Lecture 13: Adaptive Immunity Flashcards by Vic Canon

What is specific immunity?

aka the third line of defense or adaptive immunity

the body’s ability to recognize and defend itself against distinct invaders and their products

A “smart” system whose “memory” allows it to respond rapidly to a second encounter with a pathogen

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What are the types of specific immunity?

Humoral: antibodies produced by B cells

Cell-mediated: involves T cells

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What is an antigen (Ag)?

a substance that causes the body to produce specific antibodies or sensitizes T cells (from the invaders)

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What is an antibody (Ab)?

A protein made in response to an antigen (from the hosts)

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What is the overview of adaptive immunity?

lymphocyte development and differentiation
the presentation of antigens
the challenge of B and T lymphocytes by antigens
B-lymphocyte response (the production and activities of antibodies) and T-lymphocyte response (cell-mediated immunity)

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What is the lymphatic system?

Screens the tissues for foreign antigens

Composed of lymphatic vessels and lymphatic cells

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Lymph system vs blood system

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Lymphatic vessels:

Form a one-way system: conducts lymph from local tissues and returns it to the circulatory system

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What is lymph?

A liquid:
-similar composition to blood plasma

-arises from fluid leaked from blood vessels into surrounding tissues

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Lymphatic cells:

From stem cells in bone marrow

Includes lymphocytes, smallest leukocytes

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What are lymph nodes?

Houses leukocytes that recognize and attack foreign antigens present in the lymph

Concentrated in the cervical (neck), inguinal (groin), axillary (armpit), and abdominal regions

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Role of spleen as lymphatic organ

Similar in structure and function to the lymph nodes

Filters bacteria, viruses, toxins, and other foreign matter from the blood

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Role of tonsils and mucosa-associated lymphoid tissue (MALT)

Physically trap foreign particles and microbes

MALT includes the appendix, lymphoid tissue of the respiratory tract, and Peyer’s patches in the wall of the small intestine

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Discuss B lymphocytes

Arise and mature in the red bone marrow

Found primarily in the spleen, lymph nodes, red bone marrow, and Peyer’s patches

Small percentage of B cells circulate in the blood

Major function is the secretion of antibodies

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Discuss antibodies

Also called immunoglobulins (Ig)

Soluble, proteinaceous molecules that bind antigen

Secreted by plasma cells which are B cells actively fighting exogenous antigen

Part of the humoral immune response

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Discuss T lymphocytes

Produced in the red bone marrow and mature in the thymus

Circulate in lymph and blood to lymph nodes, spleen, and Peyer’s patches

Part of the cell-mediated immune response, act directly against antigens:
-endogenous invaders
-many of the body’s cells that harbor intracellular pathogens

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What are the ways that antibodies function?

Activation of complement

Stimulation of inflammation

Agglutination

Neutralization

Opsonization

Antibody-dependent cell-mediated cytotoxicity

Discuss antigens

Molecules that trigger a specific immune response
-components of bacterial cell walls, capsules, pili, and flagella
-proteins of viruses, fungi, and protozoa

Contain antigenic determinants (epitope)

Food and dust can also contain antigenic particles

What are the ways antigens can enter the body?

Through breaks in the skin and mucous membranes

Direct injection, as with a bite or needle

Through organ transplants and skin grafts

Discuss antigenic determinants

Parts of an antigen

Antibodies recognize and react with antigenic determinants or epitopes

Haptens

Small separable parts of an antigen

must specifically bind to an antibody to stimulate antibody production

Which T cell type is mainly responsible for interaction with B cells?

T helper cell 2 (TH2)

T cell type mainly responsible for interaction with B cells:

Drives B-cell proliferation; secretes IL-4, IL-5, IL-13

Which T cell type is mainly responsible for inflammation promotion?

T helper cell 17 (TH17)
Promotes inflammation; secretes IL-17; important in lung immunity

Which T cell type is mainly responsible for cell-mediated pathway?

T helper cell 1 (TH1)
Activates the cell-mediated immunity pathway;
secretes tumor necrosis factor and interferon gamma;
also responsible for delayed hypersensitivity (allergy occurring several hours or days after contact)

Which T cell type is mainly responsible for prevention of autoimmunity?

T regulatory cell (TR) Controls specific immune response Prevents autoimmunity

Which T cell type is mainly responsible for foreign cell lysis?

T cytotoxic cell (TC) Destroys a target foreign cell by lysis Important in destruction of complex microbes, cancer cells, virus-infected cells Graft rejection Requires MHC-1 for activation

What do memory T cells do? How are they formed?

Differentiate after activation of T helper or T cytotoxic cell Do not participate in initial response but seed immune tissues to be activated in future responses Always bear receptors for the specific antigen that originally activated TH or TC cell from which they are derived

What are on the surface of B cells and T cells?

B cells: Immunoglobulin; B-cell receptor; MHC II marker T cells: Distinct CD molecules: CD3, CD4/ CD8; T-cell receptor

What are antibodies?

Also called immunoglobulins (Ig) Soluble, proteinaceous molecules that bind antigen Secreted by plasma cells, which are B cells actively fighting exogenous antigen Part of the humoral immune response

Antibody function: Activation of complement:

The interaction of an antibody with complement can result in the specific rupturing of cells and some viruses

Antibody function: Agglutination

The capacity of antibodies to aggregate, or agglutinate, antigens is the consequence of their cross linking cells or particles into large clumps. Agglutination renders microbes immobile and enhances their phagocytosis.

Antibody function: Neutralization

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

Antibody function: Opsonization

When antibodies bind to microbes, they encourage the uptake of the microbe by phagocytes. Opsonization has been likened to putting handles on a slippery object to provide phagocytes a better grip.

What are the different types of antigens?

Antigenic determinants Exogenous antigens Endogenous antigens Autoantigens

Clonal Deletion:

The process of destroying B and T cells that react to self antigens

Immune Tolerance:

When lymphocytes develop a harmful specificity for self molecules, they are eliminated from the pool of cells

Clonal Selection of B cells:

Bone marrow gives rise to B cells Mature B cells migrate to lymphoid organs A mature B cells recognizes epitopes by B-cell receptors

What are the requirements for effective vaccines? If one requirement is not met, should the vaccine be used? Why or why not?

It should have a low level of adverse side effects or toxicity and not cause serious harm It should protect against exposure to natural, wild forms of pathogen It should stimulate both antibody (B-cell) response and cell-mediated (T-cell) response It should have long-term, lasting effects (produce memory) It should not require numerous doses or boosters It should be inexpensive, have a relatively long shelf life, and be easy to administer.

Advantages and disadvantages of live, attenuated vaccines?

Advantages: Viable organisms can multiply and produce infection but not disease Confer long-lasting protection Require fewer disease and boosters Effective at inducing cell-mediated immunity Disadvantages: Require storage facilities Can be transmitted to other people Can mutate to become virulent again

How are DNA vaccines made?

DNA that codes for protein antigen is extracted from pathogen genome Genomic DNA is inserted into plasmid vector; plasmid is amplified and prepared as vaccine DNA vaccine is injected into subject Cells of subject accept plasmid with pathogen’s DNA, DNA is transcribed and translated into various proteins Foreign protein of pathogen is inserted into cell membrane, where it will stimulate immune response.