Ch. 13 Host Defenses II LS

All mature T lymphocytes express ______ coreceptors. T cells also express ______ coreceptors.

CD3; CD4 or CD8 In addition to the antigen-specific T-cell receptor, all mature T lymphocytes express coreceptors called CD3. CD3 molecules surround the T-cell receptor and assist in binding. T cells also express either a CD4 or a CD8 coreceptor

Mature T cells express ______ or ______.

CD4 coreceptors; CD8 coreceptors

A basic immunoglobulin molecules is composed of how many polypeptide chains?

4

An antibody molecule is a composite of _____________ polypeptide chains, including __________ heavy chains and _________ light chains.

4; 2; 2 The basic immunoglobulin molecule is a composite of four polypeptide chains: a pair of identical heavy (H) chains and a pair of identical light (L) chains (figure 13.8). One light chain is bonded to one heavy chain, and the two heavy chains are bonded to one another with disulfide bonds, creating a symmetrical, Y-shaped arrangement.

clonal selection

A conceptual explanation for the development of lymphocyte specificity and variety during immune maturation.

True or false: There is a vaccine for almost all known pathogenic microbes.

FALSE Unfortunately, there are no effective vaccines available for a large number of pathogens that affect over 200 million people per year worldwide.

True or false: T cells, but not B cells constantly recirculate in blood and lymphatics.

FALSE they both recirculate constantly

True or false: Vaccination is the process of inoculating one individual with the dried pus from the pustules of a smallpox patient.

FALSE this process is actually correctly referred to as variolation -A hazardous, outmoded process of deliberately introducing smallpox material scraped from a victim into the nonimmune subject in the hope of inducing resistance. By the 10th century, this practice had changed to the deliberate inoculation of dried pus from the smallpox pustules of one patient into the arm of a healthy person, a technique later called variolation (variola is the name for the smallpox virus). This method was used in parts of the Far East for centuries before it was brought to England in 1721.

Which antibody fragment binds to receptors on the membranes of many different cells?

Fc

The fragment of an antibody that serves as the effector portion of the molecule as it binds to receptors on the membranes of many different cells is the ___________ fragment.

Fc or crystallizable

regions of the antibody (and identify them)

Fc region, hinge region, antigen binding site Fig. 13.8 Diagrammatic view of IgG depicts the principal functional areas (Fabs and Fc) of the molecule. Each Fab contains a hypervariable region (V) and a constant, nonvariable region (C). (b) Realistic model of immunoglobulin shows the tertiary and quaternary structure achieved by additional intrachain and interchain bonds.

The fragment of an antibody that serves as the effector portion of the molecule as it binds to receptors on the membranes of many different cells is the _______________ fragment

Fc//crystallizable

natural immunity

Any immunity that arises naturally in an organism via previous experience with the antigen. encompasses any immunity that is acquired during the normal biological experiences of an individual rather than through medical intervention.

The important antigenic characteristic of whole microbes or their parts is that they are recognized as ______.

foreign To be perceived as an antigen or immunogen, a substance must meet certain requirements in foreignness, shape, size, and accessibility. One important characteristic of an antigen is that it be perceived as foreign, meaning that it is not a normal constituent of the body. Whole microbes or their parts, cells, or substances that arise from other humans, animals, plants, and various molecules all possess this quality of foreignness and thus are potentially antigenic to the immune system of an individual. Molecules of complex composition such as proteins and protein-containing compounds prove to be more immunogenic than repetitious polymers composed of a single type of unit. Most materials that serve as good immunogens fall into these chemical categories: -proteins and polypeptides (enzymes, cell surface structures, exotoxins); -lipoproteins (cell membranes); -glycoproteins (blood cell markers); -nucleoproteins (DNA complexed to proteins but not pure DNA); and -polysaccharides (certain bacterial capsules) and lipopolysaccharides.

One important characteristic of an antigen is that it be perceived as _____________, meaning that it is not a normal constituent of the body

foreign/nonself/non-self

To become functional, most B cells must interact with T ________ cells that bear receptors for epitopes on the same antigen.

helper

Specific immunity only occurs after a(n) __________ event.

immunizing This sort of immunity is not innate but adaptive. This means it is acquired only after an immunizing event such as an infection.

Mature B and T lymphocytes migrate in and out of ____________ organs.

lymphoid

T and B lymphocytes migrate to separate areas of the ___________organs after maturation.

lymphoid

One set of genes that codes for human cell receptors and plays a role in recognition of self by the immune system is the _________ ___________ ___________ (MHC).

major histocompatibility complex (MHC) (A set of genes in mammals that produces molecules on surfaces of cells that differentiate among different individuals in the species. See HLA.) One set of genes that codes for human cell markers or receptors is the major histocompatibility complex (MHC). This gene complex gives rise to a series of glycoproteins (called MHC molecules) found on all cells except red blood cells. The MHC is also called the human leukocyte antigen (HLA) system. This marker set plays a vital role in recognition of self by the immune system and in rejection of foreign tissue.

Which type of T cell will be available to mount an immediate response upon subsequent contact with the same invader?

memory T cell A T cell is initially sensitized when an antigen/MHC complex comes in contact with T-cell receptors. Activated T cells then begin to divide, and they differentiate into one of the subsets of effector cells (cells that actually perform the ultimate action of the system) and memory cells that will be available to mount an immediate response upon subsequent contact (table 13.4). Memory T cells are some of the longest-lived blood cells known.

________ can quickly respond upon second exposure to the eliciting antigen.

memory T cells

Mature B cells and T cells ______.

migrate in and out of lymphoid tissues

Specific immunity ______.

occurs only after an immunizing event such as an infection is adaptive (not present at birth; at birth only innate immunity is present)

differentiate between the different types of immunities:

passive natural=mom transfers antibodies to her fetus active natural =u got the infection and ur body's immune system is responding artificial natural=getting the pooled blood sera from donors (IVIG) artificial active=getting a vaccine

An antigen-_______ cell is a cell that ingests and degrades an antigen and subsequently places the antigenic determinant molecules on its surface for recognition by CD4 T lymphocytes.

presenting

A conceptual explanation for the development of lymphocyte specificity and variety during immune system maturation is known as the clonal _____ theory.

selection

The process by which the B or T cell with an antigen-specific receptor is activated by that incoming antigen is called clonal ______.

selection *deletion=refers to the destruction of self-antigens *development=the B or T cell with the appropriate receptor is selected for rapid multiplication *the receptor recognizes and binds to the antigen, so that the lymphocyte is selected for rapid multiplication

A conceptual explanation for the development of lymphocyte specificity and variety during immune system maturation is known as the clonal _____ theory.

selection the mechanism by which the exactly correct B or T cell is activated by any incoming antigen. This process is called clonal selection. After activation, the B or T cell multiplies rapidly in a process called clonal expansion. Two important features of clonal selection are that (1) lymphocyte specificity is preprogrammed, existing in the genetic makeup before an antigen has ever entered the tissues, and (2) each genetically distinct lymphocyte expresses only a single specificity and can react to that chemical epitope.

After final maturation, T and B lymphocytes migrate to ____ areas in the ____ organs.

separate; lymphoid Although all lymphocytes arise from the same basic stem cell type, at some point in development they diverge into two distinct types. Final development of B cells occurs in specialized bone marrow sites, and that of T cells occurs in the thymus. Both cell types subsequently migrate to separate areas in the lymphoid organs (for instance, nodes and spleen). B and T cells constantly recirculate through the circulatory system and lymphatics, migrating into and out of the lymphoid organs

antitoxin

Globulin fraction of serum that neutralizes a specific toxin. Also refers to the specific antitoxin antibody itself.

artificial immunity

Immunity that is induced as a medical intervention, either by exposing an individual to an antigen or administering immune substances to him or her. active immunity: occurs when an individual receives an immune stimulus (antigen) that activates the B and T cells, causing the body to produce immune substances such as antibodies. Active immunity is marked by several characteristics: (1) It creates a memory that renders the person ready for quick action upon reexposure to that same antigen; (2) it requires several days to develop; and (3) it lasts for a relatively long time, sometimes for life. Active immunity can be stimulated by natural or artificial means.

What is the set of genes that encodes human cell receptors that play a role in recognition of self by the immune system called?

MHC This marker set plays a vital role in recognition of self by the immune system and in rejection of foreign tissue.

Through ______, both a primary and memory response will occur so that if the pathogen enters the body, the immune response will be immediate, powerful, and sustained.

vaccination The basic principle behind vaccination is to stimulate a primary response and a memory response that primes the immune system for future exposure to a virulent pathogen. If this pathogen enters the body, the immune response will be immediate, powerful, and sustained.

Intravenous immunoglobulin (IVIG) contains immunoglobulins extracted from ______.

the pooled blood of many human donors Intravenous immunoglobulin (IVIG), sometimes called gamma globulin, contains immunoglobulin extracted from the pooled blood of human donors. The method of processing IVIG concentrates the antibodies to increase potency and eliminates potential pathogens (such as hepatitis B and HIV). It is most useful in patients who have a diminished ability to mount their own immune response, or if the disease is so fast-acting that it could be fatal before the victim develops her own antibodies (tetanus, rabies).

When considering pathogenic microbes, ______.

there are many that lack a vaccine As of 2008, there were no vaccines used in the United States that consisted of killed whole bacteria. The last two available were those for cholera and plague. Despite considerable successes, dozens of bacterial, viral, protozoal, and fungal diseases still remain without a functional vaccine. At the present time, no reliable vaccines are available for HIV/AIDS, various diarrheal diseases, respiratory diseases, and worm infections that affect over 200 million people per year worldwide. Worse than that, most existing vaccines are out of reach for much of the world's population.

________ causes an immediate immune response upon entry of the pathogen in the body.

vaccination The basic principle behind vaccination is to stimulate a primary response and a memory response that primes the immune system for future exposure to a virulent pathogen. If this pathogen enters the body, the immune response will be immediate, powerful, and sustained. NOT: -immunization (Although often used interchangeably with vaccination, immunization includes both active artificial immunization (vaccination) and artificial passive immunity (i.e. antisera).)

passive immunity

Specific resistance that is acquired indirectly by donation of preformed immune substances (antibodies) produced in the body of another individual. occurs when an individual receives immune substances (usually anti-bodies) that were produced actively in the body of another human or animal donor. The recipient is protected for a short time, even though he or she has not had prior exposure to the antigen. It is characterized by (1) lack of memory for the original antigen; (2) lack of production of new antibodies against that disease; (3) immediate onset of protection; and (4) short-term effectiveness because antibodies have a limited period of function and, ultimately, the recipient's body disposes of them. Passive immunity can also be natural or artificial in origin.

Only ________ cells require antigen to be presented on MHC class molecules.

T *all T cells require antigen presentation *B cells do not respond to antigen presented on MHC class molecules T-cell reactions are among the most complex and diverse in the immune system and involve several subsets of T cells, whose particular actions are dictated by the APCs that activate them. We refer to T cells as "restricted"—that is, they require some type of MHC (self) recognition before they can be activated. T cells produce cytokines with a spectrum of biological effects. They also are influenced by cytokines secreted by other cells. The end result of T-cell stimulation is the mobilization of other T cells, B cells, and phagocytes.

Since they require some type of MHC recognition on an antigen-presenting cell before they can be activated, we refer to ______________ cells as "restricted".

T T-cell reactions are among the most complex and diverse in the immune system and involve several subsets of T cells, whose particular actions are dictated by the APCs that activate them. We refer to T cells as "restricted"—that is, they require some type of MHC (self) recognition before they can be activated.

Most B cells must interact with cells that bear receptors for epitopes on the same antigen to become functional. What type of cell would this be?

T helper

agglutination

The aggregation by antibodies of suspended cells or similar-size particles (agglutinogens) into clumps that settle.

neutralization

The process of combining an acid and a base until they reach a balanced proportion, with a pH value close to 7. In neutralization reactions, antibodies fill the surface receptors on a virus or the active site on a microbial enzyme to prevent it from attaching normally.

opsonization

The process of stimulating phagocytosis by affixing molecules (opsonins such as antibodies and complement) to the surfaces of foreign cells or particles. a process that makes microbes more readily recognized by phagocytes, so that they can dispose of them. Opsonization has been likened to putting handles on a slippery object to provide phagocytes a better grip.

clonal deletion

The selective elimination of lymphocytes that would recognize self markers

Which of the following is true for vaccines that have been approved and licensed for general use in preventing diseases?

The vaccines may show adverse outcomes, known as complications. Vaccines must go through many years of trials in experimental animals and human volunteers before they are licensed for general use. Even after they have been approved, like all therapeutic products, they are not without complications. The most common of these are local reactions at the injection site, fever, allergies, and other adverse outcomes. Some patients experience allergic reactions to the medium used to grow the vaccine organism (eggs or tissue culture) rather than to vaccine antigens.

The concentration of antibodies in serum is expressed as the

titer In immunochemistry, a measure of antibody level in a patient, determined by agglutination methods. We can learn a great deal about how the immune system reacts to an antigen by studying the levels of antibodies in serum over time. This level is expressed quantitatively as the titer (ty′-tur), or concentration of antibodies

A measure of antibody level in a patient's serum is called ________.

titer/titre

Deliberately inoculating a healthy person with the dried pus from the pustules of a smallpox patient is called ______.

variolation NOT: *immunization; Immunization is a process by which a person becomes protected against a disease through vaccination. *vaccination; Vaccination is a later practice that does not involve using dried pus.

Each individual mature B and T cell has the capacity to respond to ______.

a single unique antigen

Each individual mature B and T cell has the capacity to respond to ______.

a single unique antigen immunologic diversity: By the time T and B cells reach the lymphoid tissues, each one is already equipped to respond to a unique antigen. This amazing specificity is generated by extensive rearrangements of more than 500 different gene segments that code for the antigen receptors—which are antibody molecules—on the T and B cells (figure 13.4). In time, every possible recombination occurs, leading to a huge assortment of lymphocytes. It is estimated that each human produces antibodies with 10 trillion different specificities. While these DNA recombinations enable the recognition of a huge array of antigens (this is called the repertoire), keep in mind that a single naive lymphocyte can only recognize one antigen with its receptors.

The type of immunity that occurs when an individual is stimulated by an antigen that activates the T and B cell response is _______________ immunity.

active

______ immunity occurs when an individual receives an antigen that activates B and T cells, causing the body to produce immune substances such as antibodies.

active

Antibodies can cross-link cells or particles into large clumps through a process called ______.

agglutination

The aggregation (or clumping) by antibodies of whole cells or similar-size particles is called ________.

agglutination

The aggregation formed by antibodies binding cellular antigens or large particles is called

agglutination

The two arms of an antibody that bind the antigen are called _____.

antigen binding fragments

Which type of cell ingests and degrades a microbe, then processes and displays the microbe's antigens on its surface?

antigen-presenting cell In most immune reactions, the antigen must be formally presented to lymphocytes by cells called antigen-presenting cells (APCs). At least three different cells can serve as APCs: macrophages, B cells, and dendritic (den′-drih-tik) cells. Dendritic cells are the most potent and versatile of the APCs. Antigen-presenting cells grab the antigen-carrying microbe and ingest it. They degrade it and pass its antigens back out onto their membranes, complexed either with MHC-I or MHC-II markers. After processing is complete, the antigen is bound to the MHC receptor and moved to the surface of the APC so that it will be readily accessible to T lymphocytes during presentation *T lymphocytes=require presentation of processed antigen *NK cells kill virally infected cells and cancer cells that lose their MHC1 surface proteins *phagocytic cell=while all APCs are phagocytes, not all phagocytes present antigens to T cells!

The principal activity of an antibody is to immobilize, call attention to, or neutralize the ____________ that is complementary to its receptor.

antigen/epitope

Each individual mature B and T cell has the capacity to respond to a single, unique _________

antigen/immunogen/epitope

Phagocytes, such as dendritic cells, process and present ________.

antigens Antigens are presented by cells to T cells to activate a specific immune response. Tissue dendritic cells ingest the antigen and migrate to the nearest lymphoid organ (often the draining lymph nodes). Here they process antigen and present it to T and B lymphocytes. In most cases, the response of B cells also requires the assistance of special classes of T cells called T helper cells. One special class of T cells, called gamma-delta T cells, can be activated quickly by PAMPs, as seen in the innate response, or by specific antigens as seen here.

Phagocytic cells such as dendritic cells process and present ____________ to T cells.

antigens When foreign cells, such as pathogens (carrying antigens), cross the first line of defense and enter the tissue, resident phagocytes migrate to the site. Tissue macrophages ingest the pathogen and induce an inflammatory response in the tissue if appropriate. Tissue dendritic cells ingest the antigen and migrate to the nearest lymphoid organ (often the draining lymph nodes). Here they process antigen and present it to T and B lymphocytes.

An antibody that can neutralize a toxin can also be referred to as a(n)

antitoxin

A special type of antibody that can neutralize a bacterial exotoxin is called a(n) ________.

antitoxin NOT: *antibiotic: is an agent which kills bacteria *toxoid=a toxin that hsa been neutralized is called a toxoid *endotoxin=an endotoxin is a toxin that is part of gram negative outer membranes and is composed of lipopolysaccharide *antigen=the exotoxin is an antigen

Before vaccines can be marketed they go through years of trials and, upon approval, the vaccines ______.

are not without complications

Immune serum globulin contains immunoglobulins extracted from the pooled ______ of many human donors.

blood

Human B cells mature in the ________.

bone marrow

B cell maturation occurs in the _________ ___________.

bone marrow B cells develop in the bone marrow. As a result of gene modification and selection, hundreds of millions of distinct B cells develop. These naive lymphocytes circulate through the blood, "homing" to specific sites in the lymph nodes, spleen, and other lymphoid tissue, where they adhere to specific binding molecules. Here they will come into contact with antigens throughout life.

The principal activity of an antibody is to ______ the antigen for which it was formed. (Choose 3)

call attention to immobilize neutralize The principal activity of an antibody is to immobilize, call attention to, or neutralize the antigen for which it was formed. *NOT hydrolyze; Hydrolysis is an enzymatic reaction that breaks bonds between amino acids. Antibodies mark their targets for destruction but do not themselves carry it out.

After maturation, B cells and T cells ______.

constantly recirculate through both the blood and lymphatics

The region of an antibody that does not bind to antigen, designated Fc, is called the ___________ fragment.

crystallizable Let us view this structure once again, using one particular antibody type as a model. There are two functionally distinct segments called fragments. The two "arms" that bind antigen are termed antigen binding fragments (Fabs), and the rest of the molecule is the crystallizable fragment (Fc). It is called that because it was the first to be crystallized in pure form.

In an antibody molecule, one light chain is bonded to one heavy chain, and the two heavy chains are bonded to one another with _____________ bonds, creating a symmetrical Y-shaped arrangement.

disulfide

In an antibody molecule, the two heavy chains are bonded to one another through _____.

disulfide bonds