OIA1010 ADAPTIVE IMMUNOLOGY

Adaptive Immunity

Only seen in vertebrates

Requires B and T cells which are responsible for specificity while macrophages process and present foreign antigens to T lymphocytes

B and T cells express their functional activity only after a prior exposure to an antigen

B lymphocytes synthesise and secrete antibodies into bloodstream (humoral immunity)

T lymphocytes seek out the foreign particles, and interact with both B cells and Macrophages to eliminate the foreign agent (cell-mediated immunity)

Cells & Organs Invovled in Adaptive Immunity

Lymphatic Organs

Maturation, differentiation & proliferation of lymphocytes

Primary-organs: maturation of T & B cells into antigen-recognising lymphocytes

Thymus gland (T cells) & bone marrow (B cells)

Secondary-organs: antigen-driven proliferation & differentiation occur

Spleen: largest secondary lymphoid organs

Lymph nodes: small void structure (<1 cm diameter) in various region of body

Lymph nodes

Composed of medulla with many sinuses with cortex, surrounded by capsule of connective tissue.

Highly efficient in trapping antigens that enter through afferent lymphatic vessels

Cortical region contains primary lymphoid follicles to form secondary lymphoid follicles with germinal centers contain dense lymphocytes population (mostly B cells)

Lymphocytes Migration & Reticulation

Migration of lymphocytes between lymphoid & non lymphoid tissue and homes particular site highly regulated by various Cell-surface adhesion molecules (CAMs) and receptors to these molecules.

Fate of Antigen After Penetration

(1) Antigen enter body through bloodstream

Carried through circulation to spleen and interact with APCs (dendritic cells & macrophages)

Component of antigen presented to T cells that express appropriate antigen-specific TCR -> activate T cells

Splenic B cells express antigen specific BCR also activated when exposed to antigen

(2) Enter epidermal, dermal or subcutaneous tissues

Stimulate inflammatory responses: Antigen (free or trapped by APC) transported to afferent lymphatic channels into regional draining lymph node

Interaction of antigen, macrophage, dendritic cells, T cells and B cells generate immune response

(3) Enter GI or respiratory tract

Interact with MALT (Mucosa-associated lymphoid tissue) & BALT (Bronchus-associated lymphoid tissue) , macrophages and lymphocytes

Antibodies synthesized are deposited in local tissue

Lymphocytes enter efferent lymphatic and carried through thoracic duct to circulation & redistributed