Microbio Chapter 12 Adaptive Immunity

In Sum: T cytotoxic cell = foot soldier; fights on foot to carry out important work

"These warriors signal infected cells and cancer cells to commit suicide (apoptosis). Antigens in the clutches of MHC I activate these cells; that means almost any body cell as well as APCs can activate these lethal antigens. *It's not personal, I just don't want cancer, or the flu, or listeria, or..."

An antibody's single-unit, monomeric structure consists of: (3)

2 heavy chains 2 light chains Held together by covalent bonds

Stage 2: T cells Are Activated by Antigen-Presenting Cells in Lymphatic Tissues

APC bearing MHC-antigen complexes on its cell surface migrates to lymphoid tissues Interacts with T helper and T cytotoxic cells T cell with a compatible receptor binds to one of the antigens presented by the APC T cytotoxic cells will interact with antigens presented in the cleft of MHC I molecules. Only Tc cells that can specifically recognize the displayed epitopes will bind. T helper cells will bind to antigens present in the cleft of MHC II molecules. Only Th cells that can recognize the displayed epitopes will bind.

Only APCs make MHC II; they use it to present extracellular antigens to T helper cells.

APCs phagocytize dead self-cells as well as potential invaders APCs break down the ingested antigen Snippets associate with MHC II proteins to form MHC II-antigen complexes Migrate to the cell surface and display antigen

process that lymphocytes use to differentiate self from foreign MHCs

Allorecognition Tissue transplant waiting lists exist because finding an adequate match is often difficult

Similar to the need for a primary activation signal to fully activate T helper cells, a primary activation signal is needed to activate B cells by T-dependent antigens. Which of the following serves as the primary activation signal? Cytokines are released upon proper T helper cell binding. The antigen enters the cell by endocytosis and is processed, and epitopes are displayed on the cell surface by MHC II. An extracellular antigen binds to a B cell receptor. The MHC II-antigen complex on the B cell surface is bound by a T helper cell that can recognize the presented epitope.

An extracellular antigen binds to a B cell receptor. During B cell activation by T-dependent antigens, an extracellular antigen binding to a B cell receptor will serve as the primary activation signal. During the second phase, the antigen enters the cell by endocytosis and is processed, and epitopes are displayed on the cell surface by MHC II. Next, the MHC II-antigen complex on the B cell surface is bound by a T helper cell that can recognize the presented epitope. Lastly, cytokines are released upon proper T helper cell binding. previous

Which of the following molecules are only found as part of the humoral immune response? Cytotoxic T cells Antibodies T helper cells T regulatory cells

Antibodies Following activation, B cells undergo proliferation and differentiation to make memory cells and plasma cells that secrete antibodies. B cells mediate the humoral response and are not part of the cellular immune response. T helper cells coordinate both the humoral and cellular immune response; cytotoxic T cells only participate in the cellular immune response; and T regulatory cells (a subtype of T helper cells) also appear in both the humoral and cellular immune response.

__________, or amount of antibody present in the blood, is _________ during the secondary immune response. Antibody titer; lower Antibody titer; the same Immunological memory; lower Antibody titer; greater

Antibody titer; greater Primary exposure to a given antigen generates IgM antibodies first, then IgG. In a secondary response to the same antigen, activated memory cells generate a surge of IgG antibodies and only a small amount of IgM antibodies. The antibody surge is not only faster to develop than in the primary response, but the antibody titer, or amount of antibody present in the blood, is also greater during the secondary response. Furthermore, the antibodies made in a secondary response can bind the antigen even better than their predecessor antibodies, a feature that's referred to as enhanced affinity. In fact, this reactivation is so rapid and effective that we usually don't develop any symptoms and may not even realize we were re-exposed to the antigen.

Both the cellular and humoral branches can be described as going through four general stages:

Antigen presentation Lymphocyte activation Lymphocyte proliferation and differentiation Antigen elimination and memory

Produced and mature in the bone marrow (T/B) cells

B cells

In Sum: Antigen-Presenting Cells= field scout

Dendritic cells are the main APCs. These scouts search the body and collect antigens by phagocytosis. Using MHC I and MHC II, they display antigens on their cell surface and migrate to central command (secondary lymphatic tissues) to show the collected antigens to T cells. "I'll eat you and wear your antigens to dinner with the General and foot soldiers!"

the goal of both the cellular and humoral branches of adaptive immunity is the same, and that goal is to:

Eliminate an identified antigen and remember it so that next time adaptive responses are faster

how are extracellular pathogens attacked?

Extracellular pathogens are directly attacked without the need to kill host cells

Which of the following molecules released by cytotoxic T cells will enter a virus-infected cell through pores and break down proteins? Interferons Granzymes Cytokines Perforins

Granzymes Cytotoxic T cells release granzymes. They will enter a virus-infected cell through pores and break down proteins. T cytotoxic cells release perforins that form pores in the target cell. Granzymes can then enter through these pores. Cancer cells and/or infected cells released interferons to attract activated TC cells. TH cells release cytokines, which attracts NK cells and macrophages.

The degree to which the antigen provokes an immune response varies and depends on the antigen's biochemical features. Which of the following molecules are the least immunogenic? Lipids Polysaccharides Haptens Proteins

Haptens Immunogenicity is impacted by a combination of antigen size, overall molecular complexity, and chemical composition. In general, proteins tend to be more immunogenic than polysaccharides, which on average tend to be more immunogenic than lipids. However, this is a generalization, and this ranking is not a hard-and-fast rule. It depends on the molecules being compared and how the patient is exposed to the antigen. Sometimes immunogenic antigens are called complete antigens to differentiate them from antigens that are not immunogenic on their own. Haptens, or incomplete antigens, cannot stimulate an immune response unless they are linked to a more complex protein or polysaccharide.

Which of the following antibodies can cross the placenta and is the most abundant of all antibodies? IgM IgD IgG IgA

IgG The most abundant antibody in human blood, IgG constitutes up to 85 percent of total antibodies. Found in all bodily fluids, it is especially abundant in blood, lymph, cerebrospinal fluid, and peritoneal fluid. IgG is one of the most versatile antibodies we make. It is the only antibody that can cross the placenta to protect the developing fetus. IgA represents up to 15 percent of our total antibodies. Prevalent in mucus, IgA is also abundant on mucous membranes of the gut, respiratory tract, and urogenital tract. It is also found in most bodily secretions, such as tears, saliva, sweat, and milk. IgM is mainly in blood and accounts for up to 10 percent of total antibody population. Usually made early in infection upon a primary antigen exposure, its presence indicates a recent exposure to a given antigen. IgD is a very sparsely represented antibody. It is a monomer mainly found on the surface of B cells; only very small quantities can be found circulating in blood. Its precise function remains unknown.

_________can exist as either a monomer or a snowflake-shaped pentamer and is central to _________. IgA; neutralization and opsonization IgM; agglutination and precipitation reactions IgG; activating complement proteins IgE; complement activation or agglutination

IgM; agglutination and precipitation reactions IgM can exist as either a monomer or a snowflake-shaped pentamer and is central to agglutination and precipitation reactions. IgE only exists as a monomer. It is central to complement activation or agglutination. IgG only exists as a monomer and is central to activating complement proteins. IgA may exist as a monomer or dimer and has excellent neutralizing capabilities and some opsonization capabilities.

Stage 3: Activated T cells Undergo Proliferation and Differentiation

In secondary lymphoid tissues, TC and TH cells bind to an epitope presented by an APC T cells to undergo clonal expansion During these cell division events, chemical signals influence cell differentiation

Having two classes of MHCs makes sense if we consider that antigens can exist in two locations. They can exist inside a host cell as an ________________ antigen. Viral proteins inside an infected host cell Intracellular bacterium or protist Abnormal proteins made by cancer cells

Intracellular

To train T cytotoxic cells, APCs obtain viral antigen samples by being infected with the virus or by phagocytizing an infected host cell. If the APC is directly infected: (2)

It loads viral peptides with MHC I Displays them on the cell surface

Cellular and humoral responses both progress through four main stages. What is the second stage? Lymphocyte proliferation and differentiation Antigen elimination and memory Antigen presentation Lymphocyte activation

Lymphocyte activation Lymphocyte activation is the second stage through which both the cellular and humoral responses progress. Upon successful antigen presentation, lymphocytes are activated by a collection of released signaling molecules called cytokines. Activated T cells influence B cell activation. Antigen presentation is the first stage, during which dendritic cells and certain other white blood cells act as antigen-presenting cells that take up antigens, process them, and show them to T cells. Lymphocyte proliferation and differentiation is the third stage, during which activated B and T cells undergo multiple rounds of clonal expansion. Antigen elimination and memory is the fourth and last stage, in which both cellular and humoral responses collaborate to eliminate the antigen against which they were activated. Once the threat passes, effector cells die off, while memory cells endure for years in lymphatic tissues.

MHC (I / II) - found on the surface of all body cells except red blood cells Acts like the body's uniform

MHC I

MHC (I/II) interacts with CD8 on T cytotoxic cells.

MHC I

On all body cells except red blood cells; serves as the body's uniform location of MHC (I/II)

MHC I

There are two main classes of MHCs important for antigen presentation: In stage 1 of adaptive immunity, APCs use _____ or _______ to present antigens to T cells.

MHC I and MHC II

Intracellular antigens are eliminated by killing the host cell. MHC (I/II) presents intracellular antigens to T (helper/cytotoxic) cells

MHC I, T cytotoxic cells

MHC (I/II) interacts with CD4 on T helper cells.

MHC II

location of MHC (I/II) Only on antigen-presenting cells (APCs); main APCs are dendritic cells

MHC II

Extracellular pathogens are directly attacked without the need to kill host cells MHC (I/II) presents extracellular antigens to T (helper/cytotoxic) cells

MHC II, T helper

___________ are specialized "self-proteins" also known as human leukocyte antigens (HLAs)

MHCs

what are the main proteins that must be matched between a tissue donor and recipient? If they are not closely matched, then the recipient's immune system will recognize the transplanted tissue as foreign.

MHCs

As a T cell matures in the thymus it's tested. (2)

Must recognize the "self" MHC Cannot attack "self" cells

A patient fully recovered from Ebola with minor medical support. This was the result of ____________. naturally acquired passive immunity naturally acquired active immunity artificially acquired active immunity artificially acquired passive immunity

Naturally acquired active immunity Naturally acquired active immunity is stimulated when a patient recovers from disease. This form of immunity can be developed from either symptomatic or asymptomatic infections. Naturally acquired passive immunity is when someone receives antibodies to an antigen through nonmedical means. The best example is maternal antibodies passing across the placenta to a baby in utero, or maternal antibodies moving into an infant through colostrum and breast milk. Artificially acquired active immunity involves using vaccines to trigger an immune response in the patient. Vaccinations train the immune system to recognize specific antigens and result in the creation of the patient's own memory cells and antibodies. In artificially acquired passive immunity, the patient receives protective antibodies from an outside source via a medical treatment. The external source of the antibodies is often a horse, rabbit, or goat.

Antibodies 3 functions

Neutralize antigens- antibodies block toxins or antigens from binding to host cells Activate complement - complement protein attaches to pathogen. complement cascade leads to cytolysis, opsonization, and inflammation increase phagocytosis- phagocytosis is enhanced as antibodies precipitate, agglutinate, or opsonize antigens

Which of the following are not part of the adaptive immune system? Lymphocytes T-cells Antibodies Neutrophils

Neutrophils Neutrophils are part of the second line of defense or innate immune system. They are commonly elevated during acute bacterial infections. Antibodies, T-cells, and lymphocytes (a collective term for T and B cells) are part of the adaptive immune system. Adaptive responses are called into action when innate first- and second-line defenses fail to contain a threat. Adaptive responses take longer to mount, with a few days to more than a week elapsing between detection and response during the primary exposure (first interaction with that substance). Thanks to immunological memory, a secondary exposure to the same antigen is greeted by reactions that are so rapid and effective that we frequently will not even experience disease symptoms while our bodies eliminate the pathogen.

The mechanism for B cell self-tolerance screening differs from that of T cells: (2)

Occurs in the bone marrow Ensures future antibodies won't cross-react with self-antigens and damage host tissues

Stage 3 of humoral response: Activated B Cells Proliferate and Differentiate into Plasma Cells & Memory Cells

Once fully activated, B cells undergo proliferation and eventually differentiate into effector cells and memory cells -All of the resulting B cell clones recognize the exact same epitope of the antigen -Clones become effector cells called plasma cells and a small number become memory B cells that will reside in lymphatic tissues *if the B cell interacts with a T-dependent antigen, then a T helper cll is needed to advance to proliferation. *if the B cell interacts with a T-independent antigen, then the B cell can proliferate without further interactions.

MHC II: Presenting Extracellular Antigens to T Helper Cells Only which type of cells make MHC II? They use it to present extracellular antigens to T helper cells.

Only APCs make MHC II; they use it to present extracellular antigens to T helper cells.

Which of the following is not a key antibody function? Opsonization Precipitation Neutralization Phagocytosis

Phagocytosis Phagocytosis is not a key function of antibodies. However, they can increase phagocytosis by serving as opsonins (factors that bind a target antigen to tag it for phagocytosis), causing agglutination of large antigens (such as bacterial cells), and precipitating small, soluble antigens to make them readily detectible by phagocytes. Antibodies can directly neutralize antigens to prevent them from interacting with target host cells. For example, toxins, viruses, and bacteria often bind to specific receptors on host cells. When bound by antibodies, these entities cannot interact with host cell receptors. Opsonization is the term used for tagging antigens to enhance their chances of being phagocytized. Antibodies can precipitate small, soluble antigens to make them readily detectible by phagocytes.

order these 3 groups from most immunogenic to least: polysaccharides, proteins, lipids

Proteins > polysaccharides > lipids

T Cytotoxic Cell Roles in Antigen Elimination When a cell is infected with a virus or if it is cancerous, interferons are released.

Recruits activated T cytotoxic cells to the area Enhances MHC I production inside host cells Puts the immune system on high alert

An activated T helper cell becomes either an effector T helper cell or a memory T helper cell. What is the function of the effector T helper cell? Destroy infected cells, cancer cells, and transplanted tissue Release factors that help T cytotoxic cell and B cell activation Release antibodies "Remember" the specific antigen and create a memory

Release factors that help T cytotoxic cell and B cell activation The function of the effector T helper cell is to release factors that help T cytotoxic cell and B cell activation. Effector cytotoxic T cells will destroy infected cells, cancer cells, and transplanted tissue. Activated B cells will differentiate into plasma cells and memory cells. The plasma cells will release antibodies. Memory T cells are longliving and reside in lymphoid tissues to serve as "historians" for immunological memory. They rapidly reactivate the cellular and humoral responses if the same antigen is encountered again.

As the threat subsides, memory cells remain in lymphatic tissues ready to rapidly proliferate and differentiate upon a subsequent exposure. which stage of adaptive immunity is this?

Stage 4: Effector T Cells Eliminate Antigens & Memory T Cells Remain in Lymphatic Tissues

___________include a variety of bacterial toxins (e.g. staphylococcal enterotoxins and staphylococcal toxic shock toxin) and are especially potent T helper cell activators. APCs LPS Superantigens Antigens

Superantigens Superantigens include a variety of bacterial toxins (e.g. staphylococcal enterotoxins and staphylococcal toxic shock toxin) and are especially potent T helper cell activators. Superantigens are not processed and presented to T helper cells like normal antigens. Instead of being presented in the context of MHC II, these antigens directly crosslink MHC II and the T helper cell TCR to cause a bulk, nonspecific activation. Antigens are any molecule that, if presented in the right context, may stimulate an immune response. LPS is the abrreviation used for the lipopolisaccharides that are found in the outer membrane of Gram-negative organisms. They act as "endotoxins" and may stimulate the immune response. APC is the abbreviation used for an antigen-presenting cell. previous

T helper cells do not directly attack invaders, cancer cells, or infected host cells. Instead, what do they do?

Support the action of the cells that will actually do the work in the immune response: B cells, T cytotoxic cells, and innate immunity leukocytes such as macrophages and natural killer cells TH1 cells favor the action of T cytotoxic cells TH2 cells promote the humoral response

(T/B) cells have roles in both the humoral and cellular branches of adaptive immunity

T

APCs show antigen to (T/B) cells

T

Directly destroy cells that are virus infected, damaged, foreign/transplanted, or cancerous CD8+ T cells

T Cytotoxic Cells (TC)

Most abundant T cells CD4+ T cells "Help" coordinate the adaptive immune response by releasing cytokines Activate other white blood cells (e.g., B cells, macrophages, T cytotoxic cells) Main organizers of both the cellular and humoral branches of adaptive immunity

T Helper Cells (TH)

which are the most abundant T cells?

T Helper Cells (TH)

Initially produced in the bone marrow Immature T cells migrate to the thymus Undergo maturation (T/B) cells

T cells

T cell activation leads to differentiation into diverse effector cell lineages. There are two main lineages of T cells:

T cytotoxic cells T helper cells

directly destroy infected or cancerous cells (TC / TH) cells

T cytotoxic cells (TC cells)

Once activated, T helper cells may differentiate into a variety of subclasses that have specific functions. T helper (1/2) cells activate T cytotoxic cells, macrophages, and natural killer cells to destroy intracellular pathogens.

T helper 1 (TH1) cells

Once activated, T helper cells may differentiate into a variety of subclasses that have specific functions. T helper (1/2) cells stimulate B cells to make antibodies.

T helper 2 (TH2) cells

Which of the following is the primary activation signal to fully activate T helper cells? T helper cell's TCR interacts with the MHCI-antigen complex. The B7 protein on the APC's cell surface interacts with CD28 on the surface of T helper cells. T helper cell's TCR interacts with the MHCII-antigen complex. The TCR/MHC/antigen interaction is assisted by CD8 on the surface of T helper cells.

T helper cell's TCR interacts with the MHCII-antigen complex. The primary activation signal involves the T cell's TCR interacting with the MHC-antigen complex. T cytotoxic cells will only interact with MHC I-antigen complexes, and T helper cells will only interact with MHC II-antigen complexes. This TCR/MHC/antigen interaction is further assisted by CD8 on the surface of T cytotoxic cells and by CD4 on the surface of T helper cells. The secondary activation signal involves co-stimulatory proteins on the surface of the APC binding to co-stimulatory proteins on the T cell's surface. A number of cell membrane proteins on the APC and the T cell can interact to provide the secondary signal. One common co-stimulatory interaction is the binding of a B7 protein on the APC's cell surface with CD28 on the surface of T cells.

_________ are the most abundant T cells, and their function is to __________. T helper cells (CD4+); activate B cells to stimulate the humoral branch of adaptive immunity Cytotoxic T cells (CD8); seek and destroy cancer cells Cytotoxic T cells (CD8); directly destroy cells that are virus-infected T helper cells (CD4+); coordinate the adaptive immune response

T helper cells (CD4+); coordinate the adaptive immune response T helper cells (CD4+) are the most abundant T cells, and their function is to coordinate the adaptive immune response by releasing cytokines that boost activity of other white blood cells (especially macrophages), B cells, and T cytotoxic cells. T helper cells can be thought of as the generals of your immune system. They are the main organizers of both the cellular and humoral branches of adaptive immunity. There are three T helper cell subclasses: T helper 1 (TH1) cells, T helper 2 (TH2) cells, and T regulatory (Treg) cells. T cytotoxic cells (CD8+) can be thought of as the foot soldiers of the cellular branch of adaptive immunity. They directly destroy cells that are virus-infected, damaged, foreign/transplanted, or cancerous. previous

do not directly seek and destroy invaders; coordinate an adaptive immune response by stimulating other white blood cells (TC / TH) cells

T helper cells (TH cells)

An APC bearing MHC-antigen complexes on its cell surface migrates to lymphoid tissues and interacts with which of the following cells? T helper cells and T cytotoxic cells B cells and T helper cells T helper cells only T cytotoxic cells only

T helper cells and T cytotoxic cells An APC bearing MHC-antigen complexes on its cell surface migrates to lymphoid tissues and interacts with T helper cells and T cytotoxic cells. A T cell with a compatible receptor binds to one of the antigens presented by the APC. T cytotoxic cells will interact with antigens presented in the cleft of MHC I molecules, while T helper cells will bind to antigens present in the cleft of MHC II molecules.

Once activated, T helper cells may differentiate into a variety of subclasses that have specific functions. which subclass controls functions of other white blood cells (e.g., dendritic cells, mast cells, B and T cells)?

T regulatory (Treg) cells

Stage 1 of humoral response of adaptive immunity: B cells Are Antigen-Presenting Cells. B cells have two different paths to activation:

T-independent antigens and T-dependent antigens.

Leads to the cellular response Cytokines activate T cytotoxic cells (TH1 / TH2) cell response

TH1

The type of T helper cell subclass(es) that develop(s) impacts the immune system's overall defense strategy An example of this is seen in leprosy. Which cell response causes tuberculoid form that is not disfiguring and not lethal? (TH1/TH2)

TH1

The type of T helper cell subclass(es) that develop(s) impacts the immune system's overall defense strategy An example of this is seen in leprosy. Which cell response causes a lepromatous form that is disfiguring and deadly? (TH1/TH2)

TH2

(TH1 / TH2) cell response Leads to the humoral response Cytokines promote B cell maturation

TH2 cell response

In Sum: T Helper cell= the general

These commanders mainly hang out in secondary lymphatic tissues waiting for APCs to bring back processed antigens held in the grasp of MHC II. Once activated, they release cytokines that help mobilize B cells and T cytotoxic cells for the coming battle. "B cell, make antibodies! T cytotoxic cell, go seek and destroy!"

Signaling in T Cells When signal 2 is received, a signaling cascade is sparked. There are diverse co-stimulatory proteins and therefore diverse signaling cascades. The type of cascade triggered determines what class of interleukins and other factors the T cell will make. This defines what?

This defines the specialized subclass of T cell

To train T cytotoxic cells, APCs obtain viral antigen samples by being infected with the virus or by phagocytizing an infected host cell. If the infected host cell is phagocytized: (2)

Viral antigens are engulfed Viral antigens complex with MHC I for presentation to T cytotoxic cells

how can you tell T cytotoxic cells apart from T helper cells?

We can tell these T cells apart by the presence of cluster of differentiation (CD) proteins

In Sum: B cell= sharpshooter

When activated, B cells become plasma cells that pump out antibodies. A given B cell can only make antibodies that recognize one type of epitope. "Firing off 2,000 antibodies per second is hard work!"

The monomeric structure of an antibody can be described as ________-shaped and is composed of light and heavy chains that are held together by _________. Z; covalent bonds Y; hydrogen bonds Y; disulfide bridges X; ionic bonds

Y; disulfide bridges An antibody's single-unit, monomeric structure consists of two heavy chains and two light chains held together by disulfide bridges. If the antibody is viewed from a two-dimensional perspective, it would have a "Y" shape. The tips of the Y-shaped molecule are the antigen-binding sites.

classifications for adaptive immunity: artificially acquired immunity Is the individual benefiting from the antibodies the one who made them? Describe for yes or no scenarios.

Yes= artificially acquired ACTIVE immunity; vaccination triggers immune response No= artificially acquired PASSIVE immunity; antivenom neutralizes toxins

classifications for adaptive immunity: Naturally acquired immunity Is the individual benefiting from the antibodies the one who made them? Describe for yes or no scenarios.

Yes= naturally acquired ACTIVE immunity, immunity from a previous infection No= naturally acquired PASSIVE immunity, antibodies pass across the placenta

Activated (T/B) cells influence (T/B) cell activation

activated t cells influence b cell activation

Contracting an infection that triggers the patient's immune system Memory cells and antibodies are formed Confers long-term protection Can be developed from either symptomatic or asymptomatic infections natural (active/passive) immunity

active

Vaccines to trigger an immune response Result in formation of memory cells and antibodies Confers long-term protection artificial (active/passive) immunity

active

what is the third and final line of defense?

adaptive immune response

Activated B cells, also called plasma cells, make ______________, which are a secreted form of the BCR that binds to the antigen that stimulated the activation event

antibodies

B cells coordinate the humoral response by making

antibodies

Any substance that, if presented in the right context, may trigger an immune response. Mostly proteins or polysaccharides that come from a bacterium, virus, fungus, or protist.

antigen

adaptive responses are specific to a particular ____________.

antigen

Cellular and humoral responses collaborate to eliminate the antigen against which they were activated. Once the threat passes, effector cells die off. this describes which stage of adaptive immunity?

antigen elimination

what is the first stage of adaptive immunity?

antigen presentation

Cellular and humoral responses both progress through four main stages:

antigen presentation lymphocyte activation lymphocyte proliferation and differentiation antigen elimination and memory

Dendritic cells and certain other white blood cells act as __________________________ cells.

antigen-presenting cells (APCs)

preparation of antibodies developed to neutralize specific toxins or venoms

antiserum

Your patient is suffering from botulism caused by the potent toxin released by Clostridium botulinum. In addition to supportive care, the patient could also receive an ________ to neutralize the toxin and stimulate her _________. antitoxin; artificially acquired passive immunity antiserum; artificially acquired active immunity antivenom; artificially acquired passive immunity antibiotic; naturally acquired passive immunity

antitoxin; artificially acquired passive immunity In addition to supportive care, the patient could also receive an antitoxin to neutralize the toxin and stimulate her artificially acquired passive immunity. In artificially acquired passive immunity, the patient receives protective antibodies from an outside source via a medical treatment. The external source of the antibodies is often a horse, rabbit, or goat. Antiserum, a preparation of antibodies that are developed to neutralize specific toxins or venoms, is an example. Antisera include antivenom (or antivenin) administered after a venomous snakebite, and antitoxin that neutralizes a harmful bacterial toxin. Artificially acquired active immunity is stimulated by vaccines to trigger an immune response in the patient. Naturally acquired passive immunity involves the transfer of antibodies through nonmedical means, such as breastmilk from mom to infant.

T and B cells that don't exhibit self-tolerance are signaled to undergo

apoptosis

Despite "one epitope type recognized per lymphocyte" rule, antigen recognition capacity is essentially unlimited. Why?

because the body makes a vast number of T and B cells

To train T cytotoxic cells, APCs obtain viral antigen samples by (2)

being infected with the virus or by phagocytizing an infected host cell

Memory Cells Allow for Fast, Amplified Response upon Re-exposure to an Antigen. Effector cells die off once the threat subsides, but memory cells are long-lived. Memory cells reside in lymphoid tissues and provide immunological memory. Our memory cells allow for a rapid reactivation of the (cellular/ humoral/both) branch of the adaptive response if the same antigen is encountered again later.

both Our memory cells allow for a rapid reactivation of the cellular and humoral adaptive response if the same antigen is encountered again later

IgD

bound to B cells; poorly understood Sparsely represented antibody Mainly found on the surface of B cells 2-day half-life Monomer Precise function remains unknown

How are intracellular antigens eliminated?

by killing the host cell

T cell-mediated immunity is the (cellular/humoral) response

cellular

what are the 2 types of responses in adaptive defenses?

cellular response humoral response

Chemical signals cause B or T cell to undergo clonal expansion making ______________.

clones

Self-tolerance of B cells screened in bone marrow

could make antibodies to self-antigens? -yes= apoptosis -no= passes self-tolerance screening and migrates to lymphoid tissues

IgG

crosses placenta, most abundant made later in infection Constitutes 85% of antibody in human blood Found in all bodily fluids Half-life of about 21 days in circulation Detecting IgG to a particular antigen indicates the patient has been exposed to that antigen Monomer Crosses the placenta, activates complement, neutralizes antigens and is a powerful opsonin

Clones will recognize the same epitope that activated the original parent cell As APCs and T helper cells interact in lymphatic tissues, APCs release various _______________; the types released influence what T helper cell subclasses develop. Ex:TH1 cells - IL-12 and INF-γ TH2 cells - IL-2 and IL-4

cytokines

Upon successful antigen presentation, lymphocytes are activated by a collection of released signaling molecules called _________________.

cytokines

Activated T (cytotoxic/helper) cells destroy infected cells, cancer cells, and transplanted tissues.

cytotoxic

Most antigens are T (dependent/independent).

dependent they require T helper cells to fully activate B cells

(effector/memory) cells - engage in the response against the antigen

effector

Chemical signals cause B or T cell to undergo clonal expansion making clones. Some of the clones develop into _________________ cells, while others become_______________ cells.

effector, memory

B cells and T cells have 1000s of receptors on their surface. Each receptor on a cell recognizes the same ______________.

epitope

Parts of an antigen that are recognized by B and T cells

epitopes

The parts of an antigen that B and T cells recognize and mount an immune response against are called _________. antibodies haptens apoptosis epitopes

epitopes Epitopes are antigenic determinants. The broader term antigen is commonly used instead of epitope. However, when we say a lymphocyte "recognizes" an antigen, what we mean is that the cell can bind to a particular epitope on that antigen. Antibodies are Y-shaped molecules that plasma cells produce to neutralize infectious agents. Haptens are incomplete antigens that cannot stimulate an immune response unless they are linked to a more complex protein or polysaccharide. Apoptosis is the term used for "cell suicide," or programmed cell death. T and B cells that don't exhibit self tolerance are signalled to undergo apoptosis.

antigens presented on MHC II are (intracellular/extracellular) antigens

extracellular

Having two classes of MHCs makes sense if we consider that antigens can exist in two locations. They can exist outside of a host cell as an ________________ antigen.

extracellular ex: Extracellular bacteria, parasitic worms, and various fungi

IgE

fights parasites; mediates allergic responses Present in very low concentrations Found mostly in lungs, skin, and mucous membranes Half-life of 2 days Monomer only Functions to fight parasites and mediate allergic responses Causes mast cells and basophils to release allergy mediators (e.g., histamine, leukotriene)

Stage 2 of humoral response: B Cells Are Activated by T-Dependent and T-Independent Antigens Activation pathway is a two-signal mechanism: 1. __________ ____________ is the binding of the antigen to the B cell receptor (BCR) B cell with a bound receptor internalizes the antigen, processes it, and displays it T helper cells then interact with the MHC II-antigen complex on the B cell surface 2. co-stimulatory proteins interact

first signal

T and B cells recognize a wide variety of antigens due to ___________ ____________ mechanisms, a random process that gives rise to receptors that could bind to normal body cells.

gene shuffling

T Cytotoxic Cell Kills Antigen-Infected Cells When the TCR of a patrolling T cytotoxic cell binds to an MHC I-antigen complex, it releases porins and ____________. These do the following: Enter through the pore Break down host cell proteins Induce apoptosis

granzymes

Incomplete antigens. Unable to stimulate an immune response unless they are linked to a more complex protein or polysaccharide.

haptens

Activated T (cytotoxic/helper) cells release cytokines that can stimulate or suppress other white blood cells.

helper

B cells are stimulated by T (helper/cytotoxic) cells. Activated B cells (plasma cells) will secrete antibodies.

helper

Secondary immune responses requires the coordinated activity of memory B and T cells. Primary exposure to a given antigen generates IgM antibodies first, then IgG. In a secondary response to the same antigen: Activated memory cells QUICKLY generate a (high/low) titer of high affinity IgG antibodies and a (large/small) amount of IgM antibodies.

high titer of high affinity IgG antibodies small amount of IgM antibodies

antibody-mediated immunity is the (cellular/humoral) response

humoral

Adaptive immune responses closely interact with innate immune responses. If any part of the innate or adaptive system is impaired, the host is considered __________ __________.

immune compromised

Ability of an antigen to successfully trigger an immune response. Impacted by a combination of antigen size, molecular complexity, and chemical composition.

immunogenicity

Stage 4 of humoral response: Antibodies Help Eliminate Antigens Plasma cells secrete proteins called antibodies, also known as ________________. Antibodies bind to the antigen that triggered the B cell's activation.

immunoglobulins (Ig)

antigens presented on MHC I are (intracellular/extracellular) antigens

intracellular

The major histocompatibility complex type I (MHC I) _________. is found only on antigen-presenting cells interacts with CD4 on T helper cells is found on all body cells except red blood cells presents extracellular antigens

is found on all body cells except red blood cells The major histocompatibility complex type I (MHC I) is found on all body cells except red blood cells. MHC II is only found on antigen-presenting cells (APCs), interacts with CD4 on T helper cells, and presents extracellular antigens.

A given plasma cell makes antibodies that all recognize the same epitope A given B cell can't change what epitope it recognizes, it can undergo _________ __________, which alters what class of antibody is made 5 antibody isotypes: IgG, IgA, IgM, IgE, IgD. Different isotypes have different specializations and also predominate in different areas of the body.

isotype switching

function of memory Th and Tc cells

long-lived cells that remain in lymphatic tissues; quickly mount immune response upon re-exposure

adaptive responses differ from innate responses in that they take (shorter/longer) to mount.

longer

The most important adaptive immunity leukocytes (white blood cells) are

lymphocytes

IgM

made early in infection; large structure limits where it migrates Mainly in blood Accounts for up to 10% of total antibodies Half-life of about 10 days Made early in infection upon a primary antigen exposure Exists as either a monomer or pentamer Functions in agglutination, precipitation, and complement activation (not a strong opsonin)

IgA

main antibody in milk; resistant to destruction by stomach acid Accounts for up to 15% of total antibodies Half-life of about 6 days Prevalent in mucous (e.g., mucous membranes of the gut, respiratory tract, and urogenital tract) Found in secretions (e.g., tears, saliva, sweat, and milk) Exists as a monomer or as a dimer Neutralizing and opsonization capabilities

Ensuring self-tolerance involves screening for the ability to recognize ____________________ proteins.

major histocompatibility complex (MHC)

(Mature/Immature) B and T cells: Present at relatively low levels in circulation Mainly reside in lymphoid tissues

mature

(effector/memory) cells - remain in lymphatic tissues to serve as a rapid recognition of the antigen if it's encountered again later

memory

where do memory cells reside and endure for years?

memory cells reside in lymphatic tissue and respond to later antigen encounter

A mother is breastfeeding her infant son and transferring crucial antibodies to him. This will result in _________. naturally acquired active immunity artificial acquired passive immunity naturally acquired passive immunity artificial acquired active immunity

naturally acquired passive immunity Naturally acquired passive immunity is when someone receives antibodies to an antigen through nonmedical means. The best example is maternal antibodies passing across the placenta to a baby in utero, or maternal antibodies moving into an infant through colostrum and breast milk. Naturally acquired active immunity is stimulated when a patient recovers from disease. This form of immunity can be developed from either symptomatic or asymptomatic infections. Artificially acquired active immunity involves using vaccines to trigger an immune response in the patient. Vaccinations train the immune system to recognize specific antigens and result in the creation of the patient's own memory cells and antibodies. In artificially acquired passive immunity, the patient receives protective antibodies from an outside source via a medical treatment. The external source of the antibodies is often a horse, rabbit, or goat.

with immunological memory, secondary exposure to the same antigen is rapid and effective. will we experience the same disease symptoms while our bodies eliminate the pathogen?

no, frequently will not experience disease symptoms while our bodies eliminate the pathogen

Patient receives antibodies to an antigen through nonmedical means Example: maternal antibodies No memory cells or antibodies Does NOT confer long-term protection Temporary protection natural (active/passive) immunity

passive

Patient receives protective antibodies from a medical treatment Source of the antibodies is often a horse, rabbit, or goat Antiserum - preparation of antibodies developed to neutralize specific toxins or venoms Temporary protection Patient may have an immune response artificial (active/passive) immunity

passive

MHC I bind to a diverse collection of proteins in the ER— including self-proteins—and display them on the cell surface. It is up to _______________ Tc cells to determine if the protein being displayed is a normal self-protein or not.

patrolling Only T cytotoxic cells that have been trained by APCs to recognize the given antigen can effectively patrol the body and eliminate cells displaying suspicious antigens

T Cytotoxic Cell Kills Antigen-Infected Cells When the TCR of a patrolling T cytotoxic cell binds to an MHC I-antigen complex, it releases _____________ that forms pores in the target cell.

perforins

When the TCR of a patrolling T cytotoxic cell binds to an MHC I-antigen complex, what 2 things are released?

perforins and granzymes

Activated B cells differentiate into effector cells called ____________ cells.

plasma

plasma cells function vs memory cells function

plasma cells= release antibodies memory cells= long lived cells that remain in lymphatic tissues; quickly mount immune response upon re-exposure

TCR interacting with the MHC-antigen complex (primary/secondary) activation signal

primary

T cells require two signals for full activation:

primary activation signal and secondary activation signal

Few days to more than a week between detection and response

primary exposure

Activated B and T cells undergo multiple rounds of cell division to _____________ (clonal expansion).

proliferate

Self-tolerance of T cells screened in thymus.

recognize MHCs? -no= apoptosis -yes --> potentially self reactive? -yes= apoptosis -no= passes self-tolerance screening and migrates to lymphoid tissues

involves co-stimulatory proteins on the surface of the APC binding to co-stimulatory proteins on the T cell's surface ex: B7 protein on the APC's cell surface binding with CD28 on the surface of T cells (primary/secondary) activation signal

secondary

If allowed to mature, these lymphocytes would attack self-tissues To prevent that, the body has screening mechanisms that select for immune cells with _________________.

self-tolerance

each T cell can only recognize one epitope of the antigen due to TCR _________________. APCs present diverse epitopes from diverse antigens It is possible for >1 T cell to interact with the APC and become activated

specificity

T cells physically and chemically interact with B cells to fully stimulate a humoral response. which stage of adaptive immunity does this describe?

stage 2: lymphocyte activation

what are antigens that are especially potent T helper cell activators? Examples: bacterial toxins (e.g., streptococcal exotoxin, staphylococcal toxic shock toxin) Not processed and presented to T helper cells Directly crosslink MHC II and the T helper cell TCR to cause a bulk, nonspecific activation Large numbers of T helper cells are activated Release of dangerous levels of cytokines. Can lead to shock and even death

superantigens

When a B or T cell binds to a specific epitope of an antigen, what happens to the cell?

the cell becomes activated

T cell receptors (TCRs) and B cell receptors (BCRs) are antigen recognition receptors. in TCRs and BCRs, what binds to what?

the epitope binds to the antigen-binding site

at the antigen binding site, the antibody recognizes one specific epitope. where are the antigen-binding sites?

the tips of the molecule

B cells do not require APCs to show them antigens; instead they can do what?

they can directly interact with an antigen

T or F: Our immune system generates a vast array of B cells and T cells, which have the capacity to recognize virtually any antigen.

true

when do adaptive response go into action?

when innate first and second line defenses fail to contain a threat

do cancer cells frequently make proteins and/or polysaccharides antigens?

yes, cancer cells also frequently make proteins and/or polysaccharides antigens. similar to how bacteria, viruses, fungi, or protists can make proteins or polysaccharides that are antigens.

MHC II: Presenting Extracellular Antigens to T Helper Cells

1. APC takes up extracellular antigens by phagocytosis. 2. The endocytic vesicle fuses with a lysosome to make a phagolysosome, where the antigen is broken down. Vesicles carrying the MHC II then fuse with the phagolysosome. 3. Pieces of the antigen associate with MHC II. 4. The MHC II-antigen complex migrates to the cell surface to be displayed so that it can interact with T helper cells.

Humoral response of adaptive immunity

1. An extracellular antigen binds to a B cell receptor (BCR). 2. The antigen enters the cell by endocytosis, is processed, and epitopes are displayed on the cell surface by MHC II. 3. The MHC II-antigen complex on the B cell surface is bound by a T helper cell that can recognize the presented epitope. 4. Cytokines are released upon proper Th cell binding.

MHC I: Presenting Intracellular Antigens to T Cytotoxic Cells All nucleated body cells have the capacity to present intracellular antigens in the context of MHC I

1. An intracellular antigen (a viral protein in this case) is broken into fragments by the cells proteasome. 2. The fragments are transported into the endoplasmic reticulum (ER) by a transporter protein. 3. The protein fragments associate with MHC in the ER. 4. MHC I-antigen complexes make their way to the cell surface, where they are displayed for presentation to T cytotoxic cells.

Which of the following is a common feature between T and B cells? Both will undergo proliferation and differentiation to make plasma cells. Both mature in the bone marrow. Both produce memory cells after activation. Both require an antigen-presenting cell to become activated.

Both produce memory cells after activation. A common feature between T and B cells is that they both produce memory cells after activation. B cells mature in the bone marrow, T cells mature in the thymus; only B cells will require antigen-presenting cells to become activated; and only B cells undergo proliferation and differentiation to make plasma cells.

Which of the following cell surface structures may initiate B cells by T-independent antigens? Pili Fimbriae Capsules Flagella

Capsules Repetitive antigens, such as those found on the surface of certain pathogens, may act as T-independent antigens. These repetitive antigens are usually, although not exclusively, polysaccharides (examples: bacterial capsule polysaccharides). Pili, flagellae, and fimbriae are also extracellular structures, though they do not typically act as antigens.

T-Dependent and T-Independent Antigens Repetitive antigens may act as T-independent antigens; Ex: bacterial capsule polysaccharides In T-independent activation, multiple BCRs on the given B cell directly bind to the antigen

Causes proliferation and differentiation to make plasma cells Limited capacity for memory Do not tend to confer the same long-term protection as T-dependent antigens