Adaptive Immunity: Specific Defenses of the Host

Flashcards covering key vocabulary and concepts related to adaptive immunity.

Innate immunity

Defenses against any pathogen.

Adaptive immunity

Induced resistance to a specific pathogen; also known as learned or acquired immunity.

Cellular immunity

Adaptive immunity due to T cells.

Humoral immunity

Adaptive immunity due to antibodies.

Antibody (Ab)

A protein produced in response to an antigen (Ag), capable of combining with that antigen; also called an immunoglobulin.

Antigen (Ag)

A substance that causes the body to produce specific antibodies or sensitized T cells.

Epitope

Also known as antigenic determinants, these are the specific regions on an antigen that antibodies interact with.

Hapten

Small or poor antigen is combined with carrier molecules and illicits antibody production.

Immunoglobulins

Globular proteins that make up antibodies and are produced by B-cells.

IgD

Monomer antibody that initiates immune response on naive B cells; found in blood, lymph, and on B cells (0.2% of serum Abs); half-life = 3 days.

IgM

Pentamer antibody that fixes complement and agglutinates microbes; first Ab produced in response to infection; found in blood, lymph, and on B cells (5-10% of serum Abs); half-life = 5 days.

IgG

Monomer antibody that fixes complement, crosses the placenta, and enhances phagocytosis; protects fetus and newborn; found in blood, lymph, and intestine (80% of serum Abs); half-life = 23 days.

IgA

Dimer antibody that provides mucosal protection and is found in secretions (10-15% of serum Abs); half-life = 6 days.

IgE

Monomer antibody involved in allergic reactions and lysis of parasitic worms; found on mast cells, basophils, and in blood (0.002% of serum Abs); half-life = 2 days.

T-dependent antigens

Antigens presented with (self) MHC to TH cell, which produces cytokines to activate the B cell.

T-independent antigens

Antigens that stimulate the B cell to make Abs without T cell help.

Clonal selection

Process where B cells that complex with their specific antigen proliferate into plasma cells or memory cells.

Clonal anergy

Process where lymphocytes become dormant due to interaction of receptors with antigen in the absence of other markers of inflammation.

Cytokines

Cell to cell messengers that immune system cells use to communicate.

Lymphokine

A cytokine produced by a lymphocyte.

Interleukin

A cytokine that communicates only between leukocytes.

Antibody-producing plasma cells

Differentiated B cells that initially produce IgM and then seroconvert to IgG, IgA, or IgE.

Memory cells

Differentiated B cells that persist in lymphatic tissue and can quickly respond to subsequent encounters with an antigen.

T-cell receptors (TCRs)

Receptors on T cells that respond to antigens.

Antigen-presenting cells (APCs)

Cells that present antigens to T cells; concentrated in lymphatic tissues and peripheral tissues (e.g., M cells over Peyer’s patches).

T Helper Cells

CD4+ cells that produce cyokines

TH1

Produce IFN-g, which activates cells related to cell-mediated immunity such as macrophages

TH2

Activate B cells to produce antibodies

Cytotoxic T lymphocytes (CTLs)

Activated T cytotoxic cells that recognize Ag + MHC I and induce apoptosis in target cell.

T Regulatory Cells

Suppress immune response to “self” antigens

Natural Killer (NK) Cells

Granular lymphocytes destroy cells that don’t express MHC I (foreign cells)

Antibody titer

The amount of Ab in serum.

Primary response

Immune response that occurs after initial contact with Ag.

Secondary (memory or anamnestic) response

Immune response that occurs after second exposure to Ag.

Naturally acquired active immunity

Immunity resulting from infection.

Naturally acquired passive immunity

Immunity acquired transplacentally or via colostrum.

Artificially acquired active immunity

Immunity acquired through injection of Ag (vaccination).

Artificially acquired passive immunity

Immunity acquired through injection of Ab.

Serology

The study of reactions between antibodies and antigens.

Antiserum

The generic term for serum because it contains Ab.

Globulins

Serum proteins.

Immunoglobulins

Antibodies.

Gamma (γ) globulin

Serum fraction containing Ab.