Immunity ll (Adaptive)

Adaptive cell characteristics

Recognition of self

Specificity

Diversity

Memory

Recognition of self in adaptive immunity is important because ___ and are accomplished by

distinguishing self and non-self

major histocompatibility complex (MHC)

MHC specialize to

present peptides to T cell receptors

Main classes of MHC

Class 1 and class 2

Class 1 MHC Molecules

transmembrane, surface of all nucleated cells

made of alpha and beta chains with Ag binding sites

Ag binding sites of MHC can bind to

Self peptide (all other cells know its a healthy cell)

foreign peptide (marks the cell as an infected host cell)

Class ll MHC molecule

transmembrane, found on surface of antigen presening cells (APC) has alpha and beta chains with Ag binding sites

Ag binding sites on class II MHC bind to

displays foreign particles (signals infected host cell)

Specificity is the

recognition of one specific foreign substance

Recognition of specificity is associated with

antigen of foreign invaders

Examples of foreign invaders

Antigen - any substance that elicits an immune response

MAMPs, proteins, or polysaccharides on surfaces

Epitope

Epitope

specific regions/component that binds to antibodies on the antigen

Innate defense

non-specific, 1st line of defense, active without previous exposure A

Adaptive defenses

Specific, acquired after exposure, response to antigens (Ag), involves B and T cells

Sequence the process of MHC ll

l. Lysosomes fuse with the phagosome and digest the bacterium

ll. Immunodominant epitopes are associated with MHC ll and presented on the cell surface

lll. A bacterium is engulfed by phagocytosis into a dendritic cell (APC) and is encased in a phagosome

lll > l > ll

Diversity

the recognition of trillions of unique substances

Memory results

of the actions of memory B and T cells

Memory is critical for

fighting infections faster and stronger if re-exposed to the same pathogen/substance

Sequence T cell development

l. CLP cells migrate to the thymus to become fully developed but not active/naive

ll. Common lymphoid progenitor (CLP) cells in bone marrow

lll. CLP migrate to lymph nodes and spleen to be activated when Ag is presented

ll > l > lll

Classes of T cells

Helper, regulatory, and cytotoxic T cells

CD molecules

clusters of differentiation, glycoproteins on the surface of T cells

Helper T cells CD molecule, mode of activation, function

CD4

APCs presenting Ag associated with MHC ll

Coordinate B cells and T cell responses

Regulatory T cells CD molecule, mode of activation, function

CD4

APCs presenting Ag associated with MHC ll

Downregulate strong responses

Cytotoxic T cells CD molecule, mode of activation, function

CD8

APCs/infected nucleated cells presenting Ag associated with MHC l

Destroy infected cells

T-cell receptor (TCR)

Detects Ag fragments presented by MHC molecules

Components of TCR

Sequence activation and differentiation of helper T cells

l. APC and T cells secrete cytokines to activate T cells

ll. Interaction of CD4 with MHC ll

lll. Proliferation (mitosis) and differentiation of T cells

lV. TCR recognition of a specific epitope presented by MHC ll

lV > ll > l > lll

Sequence the activation and differentiation of cytotoxic T cells

l. Interactions of CD8 with MHC l

ll. TCR recognition of specific epitope presented by MHC l

lll. Proliferation (mitosis) and differentiation

lV. APC and T cells secrete cytokines to activate T cells

V. Release of granzymes

ll > l > lV > lll > V

Sequence B cells differentiation

l. Migration to the lymph nodes and spleen to be activated if presented with Ag

ll. CLP matures in bone marrow to be fully developed

lll. Common lymphoid progenitor (CPL) cells in bone marrow

lll > ll > l

Components of B-cell receptors

Activation of B cells

BCR interacts with specific (few) Ag

No memory cells required, thus fast processing

Sequence T cell-dependent activation

l. T cell activate and stimulates the release of cytokines that then activate B cells

ll. B cells recognize and internalize an Ag

lll. Activation of B cells triggers proliferation and differentiation into B cells and plasma cells

lV. B cell presents Ag to helper T cell through MHC ll that is specific to the same Ag

V. Helper T cell interacts with Ag presented by B cells

ll > lV > V > l > lll

Difference between T cell-dependent and independent B cells

Dependent requires the involvement of a helper T cell