Adaptive Immunity (01/30)

Third line of defense

Adaptive immunity

Consists of lymphocytes and antibodies

Provides long term security against reinfection

Adaptive immunity characteristics

Inducible, specific, long lived and systemic, and has memory

Active immunity

Exposure to antigen

Immunization

Passive immunity

Preformed antibodies or T cells are administered

Clonal diversity

Production of T/B lymphocytes before birth

Creates diverse immune cells

Clonal selection

Antigen processing and presentation

Activate specific immune cells fter infection

Results in the expansion of the correct B/T cell for the infection

B cell development

Production, proliferation, differentiation in the bone marrow

Travel to lymphoid tissue and reside there as immunocompetent cells

B cells develop B cell receptors (BCR) complexes as they mature, reading for specific antigens

Each cell responds to only one specific antigen

T cell development

The thymus is the central lymphoid organ of T cell development

Development of antigen specific T cell receptors (TCR)

Leave the thymus and travel to lymphoid tissue as mature immunocompetent cells

Antigen processing and presentation

Initiated when T and B cells interact with an antigen

Must first be processed and then presented by antigen processing cells

Differentiation of T cells into cytotoxic T cells and helper T cells

MHC Class I

Presents endogenous antigen

Recruits CD8+ T cells

MHC Class II

Presents exogenous antigen

CD4+ T cells

B cell activation

When an immunocompetent B cell encounters an antigen for the first time, B cells with specific BCR are stimulated to differentiate and proliferate

A differentiated B cell becomes a plasma cell

A plasma cell is a factory for antibody production

Antigen

Molecule that can bind with antibodies, receptors, and T/B cells

Immunoglobulin/Antibodies

Produced by plasma cells

IgG, IgA, etc.

IgG

Most abundant class (80-85%)

Accounts for most of. the protective activity against infections

Transported across the placental and protects infant for the first 6 months of life

Neutralizes toxins

General, great, guard

IgA

Found in blood in bodily secretions

Airways, alimentary, anti adhesion

IgM

Largest of the immunoglobulins

First antibody produced during the primary response to an antigen (first to respond)

Synthesized during fetal life

Massive, main, micro

IgD

Low concentration in the blood

Located primarily on the surface of developing B lymphocytes acting as an antigen receptor

Differentiation, development, defuse

IgE

Defender against parasites

Mediator of common allergic responses (Allerg-E)

Direct antibody binding (through action of antibody alone)

Neutralizing, agglutination, and precipitation

Indirect antibody binding (requiring activation of other components)

Inflammation, phagocytosis, complement system activation

Th1 cell

Help develop B cells

Th2 cell

Help develop B cells

Th17 cell

Activate macrophages

Treg cells

Limit immune response

Cytotoxic T cells (Tc)

Instead of interacting with APC, the immunocompetent Tc cell recognizes antigens presented by MHC Class I molecules on the surface of the cell

Destroy cancer cells or cells infected with a virus

Primary response

Initial exposure

Latent period or lag phase

After 5-7 days, an IgM (first antibody) antibody for a specific antigen is detected

Secondary exposure

More rapid

Larger amounts of IgG is produced

Rapidity is caused by the presence of memory cells that do not have to differentiate

Aging and immune function

Decreased T cell activity

Decreased antibody response to antigens