Ch. 24

The steps of how a cytotoxic T cell kills an infected cell

1) A cytotoxic T cell binds to an infected cell, which then synthesizes several toxic proteins that act on the bound cell, including one called perforin 2) Perforin is discharged from the cytotoxic T cell and attaches to the infected cell's plasma membrane, making holes in it. T cell enzymes then enter the infected cell and promote its death by a process called apoptosis 3) The infected cell is destroyed (lysed), and the cytotoxic T cell may move on to destroy other cells infected with the same pathogen

Two requirements for a helper T cell to activate adaptive immune responses

1) A foreign molecule must be present that can bind specifically to the antigen receptor of the T cell 2) This antigen must be displayed on the surface of an antigen-presenting cell

Two types of adaptive responses

1) Defense against pathogens in body fluids 2) Defense against pathogens inside body cells

The steps of the activation of a helper T cell

1) The macrophage ingests a microbe and breaks it into fragments--foreign antigens. Then molecules of a special protein belonging to the macrophage, which we will call a self protein, 2) bind the foreign antigens--nonself molecules--and 3) display them on the cell's surface. Serve as identity markers for our body cells. 4) Helper T cells recognize and bind to the combination of a self protein and a foreign antigen--called a self-nonself complex--displayed on an antigen present cell.

Activated helper T cells promote the immune response, with the secretion of additional stimulatory proteins. These signaling molecules, secreted by helper T cells, have three major effects:

1) They stimulate clonal selection of the helper T cell, producing both memory cells and additional effector helper T cells 2) The signals help activate B cells, thus stimulating the humoral immune response 3) Signaling molecules stimulate the activity of cytotoxic T cells of the cell-mediated immune response

Steps of inflammatory response

1) Tissue injury; signaling molecules are released from mast cells and macrophages that affect capillary cells 2) Capillaries widen and become leaky. Neutrophils migrate to the infected area 3) Neutrophils digest bacteria and cell debris at the site, and the tissue heals

Steps of allergic reaction

1) an allergen enters the bloodstream, binds to effector B cells 2) The B cells then proliferate through clonal selection and secrete large amounts of antibodies to this allergen 3) Antibodies attach to a mast cell that produce histamine and other chemicals, which trigger the inflammatory response 4) The allergen binds to antibodies on a mast cell 5) Histamine is released, causing allergy symptoms

The two ways the immune system responds to a detected antigen

1) an increase in the number of cells that attack to the invader directly 2) or produce antibodies

Two functions of an antibody in the humoral immune response

1) recognize and bind to a certain antigen 2) to assist in eliminating that antigen

Steps of the interferon mechanism against viruses

1) the virus infects a cell 2) interferon genes in the cell's nucleus are turned on 3) the cell synthesizes interferon. The infected cell then dies 4) the interferon proteins of the dead cell may diffuse to neighboring healthy cells, 5) which stimulates them to produce other proteins that inhibit viral reproduction

The complement system in antigen-antibody complex

Activated complement proteins can attach to a foreign cell. Once there, several activated proteins form a complex that pokes a hole in the plasma membrane of the foreign cell, causing cell lysis. Other complement proteins will act as chemical alarm signals to recruit more immune cells to the site of infection and promote inflammation

Neutralization

Antibodies bind to surface proteins on a virus or bacterium, thereby blocking a pathogen's ability to infect a host cell and presenting an easily recognized structure to macrophages. This increases the likelihood that the foreign cell will be engulfed by phagocytosis.

Function of antibodies

Antibodies do not kill pathogens. Antibodies mark a pathogen by combining with it to form an antigen-antibody complex. Weak chemical bonds between antigens and the antigen-binding sites on antibodies hold the complex together. Once marker, other immune system components bring about the destruction of the antigen

Precipitation

Antibodies link together dissolved antigens rather than viruses or cells. Antigens separate, in solid form, from the surrounding liquid. Enhances phagocytosis.

Lymph in Immune Function

As lymph circulate through the lymphatic organs, such as the lymph nodes, it carries microbes, parts of microbes, and their toxins picked up from infection sites anywhere in the body. Once inside lymphatic organs, macrophages that reside there permanently engulf the invaders as part of the innate immune response. Lymph nodes fill with huge numbers of defensive cells (many of which are lymphocytes, which are responsible for the adaptive immune response)

Septic shock

Bacterial infections in blood can cause this. It affects capillaries of the whole body--their leakiness leads to widespread fluid accumulation in tissues and low blood pressure, which may ultimately lead to poor circulation to vital organs and organ failure.

What cells help protect the body against the spread of some cancers

Cytotoxic T cells

What do anti-inflammatory drugs do

Dampen the normal inflammatory response and help reduce swelling and fever

Large amounts of _________ is needed to maintain the number of copies of antibodies

Endoplasmic reticulum

Lymph in circulatory system

Fluid that enters the tissue spaces from the blood in a capillary bed is returned to the blood via lymphatic vessels. Fluid enters the lymphatic system by diffusing into dead-end lymphatic capillaries that are intermingled among the blood capillaries. Lymph drains from the lymphatic capillaries into larger lymphatic vessels. The fluid reenters the circulatory system via two lymphatic vessels that fuse with veins in the chest. The lymphatic vessels have valves to prevent back flow, and these vessels depend mainly on the movement of skeletal muscles to squeeze their fluid along

Other functions of T cells

Function indirectly by promoting phagocytosis by other white blood cells and by stimulating B cells to produce antibodies.

How HIV destroys helper T cells

Proteins on the surface of the virus can bind to proteins on the surface of a helper T cell. Attached, HIV can enter and begin to reproduce

What can enhance the activation of the helper T cell

Signaling molecules secreted by the antigen-presenting cell, which diffuse to the helper T cell and stimulate it

Components of innate external barriers

Skin/exoskeleton, acidic environment, secretions, mucous membranes, hairs, cilia

Agglutination

The clumping together of viruses, bacteria, or foreign eukaryotic cells. Because each antibody has at least two binding sites, antibodies can hold a clump of invading cells together. It makes the cells easy for phagocytes to capture.

Fever

Toxins themselves may trigger this, or macrophages may release compounds that cause the body's thermostat to be set at a higher temperature. A high one is dangerous, but a moderate one may stimulate phagocytosis and hasten tissue repair

histamine

a chemical alarm signal released by mast cells that causes blood vessels to dilate and become more permeable in inflammatory and allergic responses

Anaphylactic shock

a dangerous allergic reaction --cause mast cells to release inflammatory chemicals very suddenly. Blood vessels then dilate abruptly, causing a rapid drop in blood pressure. Can be counteracted with epinephrine.

Complement system

a group of about 30 different proteins that circulate in an inactive form of the blood. These proteins can act together with other defense mechanisms. Some cause lysis (bursting) of invading cell, some enhance phagocytosis, and some trigger the inflammatory response

Innate immunity

a set of defenses that are active immediately upon infection and are the same whether or not the pathogen has been encountered previously

antigenic determinant (epitope)

a small surface-exposed region of an antigen. Antigen receptors on B cells, as well as antibodies, recognize and bind to the antigenic determinant

All antibody mechanisms involve two parts

a specific (adaptive) phase and a nonspecific (innate) phase

Effector cells (plasma cells)

act immediately to combat infection. Secrete antibodies into blood and lymph

Pathogens

agents that cause disease

Antibody

an immune protein found in blood plasma that attaches to one particular kind of antigen and helps counter its effects

Elevated white cell count indicates

an infection because white blood cells increase severalfold

Depending on the polypeptide structure of the stem,

antibodies are grouped into various classes that distinguish where they are found in the body and how they work

Allergens

antigens that cause allergies

Inflammatory response

any damage to tissue triggers this response. Its main function is to disinfect and clean injured tissues

Antigen

any molecule that elicits an adaptive immune response. They are non-self molecules that protrude from pathogens or other particles, such as viruses, bacteria, mold spores, pollen, house dust, or the cell surfaces of transplanted organs, or substances released into extracellular fluid, such as toxins secreted by bacteria

Antihistamines

are drugs that interfere with histamine's action and give temporary relief from an allergy

Macrophages

are large and wander through interstitial fluid eating an bacteria and viruses they encounter

Immunodeficiency disorders

are under reactions of the immune system, in which an immune response is either defective or absent (ex: SCID, AIDS, Hodgkin's disease)

Common disorders associated with chronic inflammation

arthritis, heart disease, Alzheimer's disease, and some cancers

Natural killer cells

attack cancer cells and virus-infected cells by releasing chemicals that lead to cell death

Cytotoxic T cells

battles pathogens that have already entered body cells CD8, MHC 1

As HIV depletes the number of helper T cells,

both the cell-mediated and humoral immune responses are severely impaired, drastically compromising the body's ability to fight infections

phagocytosis

cellular ingestion and digestion of foreign substances

B and T cells of the adaptive immune response together provide a two-pronged defense:

combatting pathogens both in body fluids and cells

vaccine

composed of a harmless variant or part of a disease-causing microbe, such as an inactivated bacterial toxin, a dead or weakened virus, or a piece of a virus. The vaccine stimulates the immune system to mount defenses against this harmless antigen, defenses that will also be effective against the actual pathogen because it has similar antigens. Once vaccinated, your immune system will respond quickly if it is exposed to the actual microbe

pus

consists of dead white blood cells, fluid that has leaked from capillaries, and other tissue debris

Helper T cells activate

cytotoxic T cells

Hairs

filter incoming air

The tip of each arm of the Y

forms an antigen-binding site

Each antibody molecule consists of

four polypeptide chains

Major Histocompatibility Complex (MHC) molecules

genes at multiple chromosomal loci code for these, which are the main self proteins

HIV destroys what kind of cells

helper T cells

Allergies

hypersensitive (exaggerated) responses to otherwise harmless antigens in our surroundings

The structure of an antigen-bind site on an antibody is ____ to that of the receptor on the parent B cell

identical

Active Immunity

immunity from exposure or vaccine that actively produces antibodies

vaccination

immunization

Vertebrates rely on

innate and adaptive immunity

Invertebrates rely solely on

innate immunity

lymphatic system

involved in both innate and adaptive immunity. It consists of a branching network of vessels, lymph nodes, bone marrow, and several organs

Adaptive Immunity (acquired immunity)

is a set of defenses that is activated in response to specific pathogens. It differs from individual to individual depending on what pathogen they have previously been exposed to. It is highly specific and it can amplify innate responses

Memory cells

lie in wait to help activate the immune system upon subsequent exposure to the antigen. Remain in lymph nodes

Mucous membranes

line internal surfaces open to the external environment (digestive, respiratory, reproductive, and urinary). The mucus produced provides protection by trapping foreign particles and using defensive proteins to kill harmful microbes.

lymph nodes

little round organs packed with macrophages and lymphocytes

Adaptive responses are

lymphocytes

B cells

lymphocytes that continue developing in bone marrow

T cells

lymphocytes that migrate to the thymus to develop

Two types of antigen-presenting cells

macrophages and B cells

All classes of antibodies..

mark invaders for elimination

Binding of antibodies to antigens boosts the function of phagocytic cells of innate immunity in three ways:

neutralization, agglutination, and precipitation

Binding of antibodies to antigens inactivates antigens by:

neutralization, agglutination, precipitation, and activation of complement system

Two main types of of phagocytic cells

neutrophils and macrophages

A T cell receptor has two binding sites:

one for antigen and one for self protein. Both enable a T cell receptor to recognize the overall shape of a self-nonself complex on an antigen-presenting cell

Antigen-presenting cell (APC)

one of a family of white blood cells that ingests a foreign substance or a microbe and attaches antigenic portions of the ingested material to its own surface, thereby displaying the antigens to a helper T cell

Humoral Immune Response

one of the two adaptive responses produced by B cells. It defends primarily against bacteria and viruses present in body fluids. It involves the secretion of free floating antibodies by B cells into the blood and lymph. This response can be passively transferred

Components of the innate internal defenses

phagocytic cells, natural killer cells, defensive proteins, inflammatory response

antigen receptors

protein molecules that stick out from a cell's surface, capable of binding one specific type of antigen, and are in place before antigen is encountered

Most antigens are

proteins or large polysaccharides that protrude from the surfaces of viruses of foreign cells

Interferons

proteins produced by virus-infected cells that help to limit cell-to-cell spread of viruses

The secondary is ____ and more _____ than the primary

quicker, prolonged

Autoimmune disorders

result when the immune system turns against some of the body's own molecules (ex: lupus, rheumatoid arthritis, type I diabetes, MS, Chron's disease).

Two stages of allergic reactions

sensitization and later exposure to the same allergen

lymph

similar to interstitial fluid but contains less oxygen and fewer nutrients

Adaptive responses are ___ than innate responses

slower

Phagocytes have

surface receptors that bind to fragments of foreign molecules shared by a broad range of pathogens

Cilia

sweep mucus in the trachea and any trapped microbes upward and out

B and T cells differentiate by

synthesizing many copies of a specific protein, which are then incorporated into the plasma membrane to form antigen receptors

Passive Immunity

temporary immunity obtained by acquiring ready-made antibodies (through placenta, breast milk, antivenom)

What enables our adaptive immune response to battle foreign invaders without harming healthy cells

the ability of lymphocytes to recognize the body's own molecules

Herceptin

the antibody used to slow the progress of cancer

Immune system

the body's system of defenses against agents that case disease

The antigen-antibody complex promotes another innate immune response, other than phagocytosis...

the complement system

MHC markers can cause

the failure in organ transplants because the person's T cells recognize the MHC markers on the donor's cells as foreign

Primary immune response

the first time an antigen enters the body and selectively activates lymphocytes. This is the initial response of adaptive immunity. It is slow. The memory cells produced by clonal selection during this confer protection in subsequent encounters with that pathogen

Human Chorionic Gonadotropin (hCG)

the hormone detected by an antibody in home pregnancy tests.

Neutrophils

the most abundant type of white blood cell, circulate the blood and enter tissues at sites of infection

chronic inflammation

the persistence of inflammatory components for abnormally long periods

Clonal selection

the process by which an antigen selectively binds to and activates only those lymphocytes bearing receptors specific for the antigen. The selected lymphocytes proliferate and differentiate into a clone of effector cells and a clone of memory cells specific for the stimulating antigen

Cell-mediated Immune Response

the second type of adaptive immunity, produced by T cells. It defends against infections inside body cells. T cells destroy body cells infected with bacteria or viruses.

Antigen-binding site

the specific region on an antigen receptor or antibody that recognizes an antigenic determinant. An antigen usually has several different determinants

Lymphocytes

the white blood cells responsible for adaptive immunity. They are found in blood and also the tissues and organs of the lymphatic system

After B and T cells fully develop..

they move via the bloodstream to lymph nodes, spleen, and other parts of the lymphatic system

Two main functions of the lymphatic system

to return tissue fluid back to the circulatory system and to fight infection

Antibodies are used to

treat breast cancer and home pregnancy tests

helper T cell

triggers both the humoral and cell-mediated immune responses. They themselves do not carry out those responses, but signals from them initiate the production of antibodies that neutralize pathogens and activate cytotoxic T cells that kill infected cells. Without these, there is virtually no immune response. CD4, MHC 2. B-cell macrophages/dendritic cells

Secondary immune response

when memory cells produced during the primary response are activated by a second exposure to the same antigen. Memory cells produced by the primary enable the rapid formation of a second round of clonal selection. This second round of clonal selection is faster and stronger than the first. The pool of memory cells produced by the primary gives rise to great quantities of effector cells that quickly secrete high levels of antibodies when a "known" antigen enters the body

Innate immune cells are

white blood cells