Part 4: Adaptive (acquired) Immunity Flashcards by Beck Forsland

What are the characteristics of adaptive immunity?

Specificity
Self recognition
Memory

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In the adaptive (acquired) immune response, the ability to distinguish cells from self and non-self is called

Self recognition

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In the adaptive (acquired) immune response, what does specificity refer to?

Recognition of foreign substances

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A small molecule called a _____ can also act as an antigen, but only when bound to a larger molecule

Hapten

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In the adaptive (acquired) immune response, what does memory refer to?

After the 1st exposure to antigen (primary response), the immune system develops memory to provide a rapid secondary response to the same antigen

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What is the 2-part strategy for eliminating foreign material?

Humoral response

Cell-mediated response

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The response that eliminates antigens that are extracellular (ie bacteria in the bloodstream)

Humoral response

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The response that deals with antigens residing within a host cell, for example a virus infected cell

Cell-mediated response

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What is an ANTIbody GENerator?

Antigen

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What is the structure of antigen?

Large carrier molecule with epitopes projecting from surface

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Antigenic determinants are

Epitopes

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Antigens come from two places

Exogenous

Endogenous

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Antigens that have entered the body from the outside (plus give examples)

Exogenous

Examples: inhalation, ingestion, injection

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Antigens that have been generated within the cell, as a result of normal cell metabolism or because of viral or intracellular bacterial infection

Endogenous

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What does it mean to say that antigens can be cross reactive?

They elicit and bind to same antibody

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What type of antigen does not behave normally and, instead of attaching to MHC groove and triggering normal immune response, they attached to the sides of the binding site?

Superantigens

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What happens because of superantigens irregular attachment?

T-cells go on an unregulated rampage, releasing regulatory molecules (cytokines) — like interferons — in toxic amounts

For example: bacterial toxins, especially Staphylococcus and Streptococcus

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What do epitopes do?

Interact with antibody and T cells

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The ___ is a cluster of many genes for antigen recognition

Major Histocompatibility Complex (MHC)

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In humans, where is the HLA complex (Human Leukocyte Antigen) the human MHC?

Genes on chromosome 6

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What class of MHC presents antigens from inside cell (endogenous proteins)

Class I MHC

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MHC I is found on

All nucleated cells

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What class of MHC presents antigens from outside the cell?

Class II MHC

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MHC II proteins display _______ which will be recognized by helper T cells

Non-self

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MHC II proteins found ONLY on immune cells called

Antigen presenting cells (APCs)

Antigen presenting cells have what kind of classes?

Both MHC I and MHC II

Antigen presenting cells (have both MHC I and MHC II) includes:

Activated dendritic cells Activated macrophages Activated B cells

The Major Histocompatibilty Complex (MHC) is divided into:

3 regions: MHC I, MHC II, MHC III

What antigen presenting cell is found in tissues that are in contact with the environment?

Activated dendritic cells

Give examples of where activated dendritic cells are found

In the skin (Langerhans cells) and lining of nose, lungs, stomach and intestines

What antigen presenting cell presents antigen early in infection?

Activated macrophages Note: Activated B cells are used later in infection

How does the presence of antigen activate macrophages?

- increased number of lysosomes (organelle filled with digestive enzymes) - produce cytokine called interleukin-1 which can induce fever and activate other cells

After the activated macrophage digests the antigenic material, what shows up on the macrophage surface?

Epitopes from antigen in combination with MHC proteins (MHC I and MHC II)

When activated macrophage presents epitopes from antigen in combination with MHC proteins (MHC I and MHC II), what cell notices and what happens?

- Helper T cells recognize presented antigen | - Recognition activates the helper T cell

What antigen presenting cells is activated later in infection as antigen presenting cell (APC)?

Activated B cells

In order to produce cytokines, Helper T cells must recognize

MHC II

What regulates cell mediated and humoral immunity?

Activated helper T cells NOTE: Cell mediated: T cell and Humoral: B cell, antibody

In order for B cells to produce antibody, they must interact with

Activated T cell

Cellular immunity is mediated by

T lymphocytes (T cells)

T cells never produce

Antibody Note: T cells never interact with free antigen, antigen must be presented to T cell by another cell

Inactive (naive) T cells cannot

Migrate into tissue

Activation of T cell require 2 signals

1. Encounter antigen presented on cell in antigen-MHC complex 2. Must be concurrently stimulated (co-stimulated) by other molecules

Activation of T cell leads to 2 things

1. Formation of specific effector T cell types | 2. Effector T cells have different roles in cell mediated immunity

What are the functions of activated T cells?

1. Proliferate 2. Bring antigens to naive T cells 3. Release cytokines

One function of activated T cell is to release cytokines. Why?

Cytokines act as messengers, they do not respond to specific antigen. They recruit other cell types, particularly macrophages

All T cells are identical in appearance, but there are 2 distinct functional populations

CD4 T lymphocytes | CD8 T lymphocytes

T cells that carry the CD4 marker can be

T helper cells (TH)

The role of TH cells is what?

Judge the significance of antigen presented by APCs (antigen presenting cells) Note: These APCs have MHC class II molecules which are recognized by TH (T helper cells)

2 subsets of TH cells

TH1 - judge and orchestrate cell mediated response by releasing cytokines to stimulate proliferation of T cells TH2 - judge and stimulate proliferation of B cells (humoral immunity)

Outcome of TH1 vs TH2 cells?

Cell activity (cell mediated) and indogenous antigen VS antibody (humoral) and exogenous antigen

What are T regulatory cells?

They can stop the action of a T cell. Treg cells stimulated by cytokine interleukin 2(IL-2) and 10 (IL-10)

Most T cells have CD8 marker, including

Cytotoxic and memory cells

T cytotoxic cells induce ____ in what kind of cells?

Apoptosis in “self” cells infected with virus or other microbes

How do T cytotoxic cells recognize dysfunctional self cells?

By recognition of antigen presented on MHC 1 molecules

T memory cells are what kind of cells?

Long lived, antigen activated T cells that respond with heightened reactivity to 2nd exposure with specific antigen

Type IV hypersensitivity immune response is mediated by

Cellular immunity

What happens when there is an imbalance in numbers of CD4 and CD8 cells?

Compromised cellular immunity

Cytokines produced by lymphocytes act as

Chemical messengers and activate other cell types

What cell types does a cytokine activate?

- Macrophages - Polymorphonuclear Leukocytes (granulocyte s) - Lymphocytes

Humoral immunity is mediated by

B lymphocytes/cells

B cells develop in

Bone marrow

Immunoglobulin (antibody) classes:

IgG - binding to antigen results in opsonization IgM - first class to be produced in response to antigen IgA - found in mucosal associated tissue with T cells IgE - can cause anaphylactic shock IgD - does not bind complement

What immunoglobulin crosses the placental barrier to provide passive immunity to fetus? (And is also in colostrum)

IgG - monomer (aka gamma globulin)

What is the most efficient class of immunoglobulins at activating complement cascade? And also agglutination and precipitation

IgM - pentamer

What immunoglobulin is found in body secretions? (Saliva, mucus, milk, tears)

IgA Note: exists as monomer in blood, secreted as a dimer

Which immunoglobulin class is involved in allergy, and triggers release of histamines by binding mast cell?

IgE - monomer

What class of immunoglobulin is primarily found on B cell surfaces where if functions as a receptor for antigen?

IgD

What is the function of complement? (Hint: OIL)

1. Opsonization preparing cells for phagocytosis 2. Inflammation, release active substances to promote 3. Lyse cell by attaching to cell surfaces, forms membrane attack complex (MAC)