Cells & Tissues of the Adaptive Immune System

Adaptive Immunity Lymphocytes

T and B lymphocytes.

B-Cell Receptor (BCR)

A membrane-bound immunoglobulin (Ig) that recognizes specific antigens.

T-Cell Receptor (TCR)

The antigen-specific receptor expressed on the surface of T cells.

Cluster of Differentiation (CD)

Cell surface molecules that serve as markers for specific cell types.

Primary Lymphoid Organs (Function)

Sites of lymphocyte development and generation of antigen-specific receptor diversity. (thymus and bone marrow)

Secondary Lymphoid Organs (Function)

Sites where lymphocytes meet antigens, undergoing clonal selection and expansion.

Secondary Lymphoid Organs (Examples)

Lymph nodes, spleen, and mucosa-associated lymphoid tissue (MALT).

Site of T Cell Development

Thymus.

Sites of B Cell Development

Bone marrow (most mammals), bursa of Fabricius (birds), or ileal Peyer's patches (ruminants).

Antigen Source for Lymph Nodes

Antigens delivered from surrounding tissues.

Antigen Source for the Spleen

Antigens delivered directly from the blood.

Antigen Source for MALT

Antigens delivered at mucosal sites.

Thymus Structure & Location

Lobulated organ in cranial mediastinum with cortex, medulla, and epithelial cell network.

Subtypes of MALT

NALT (nasal), GALT (gut), and BALT (bronchial).