25.4 : 淋巴细胞和组织

Lymphoid cells and lymphoid tissues are the two major components of lymphoid organs.

Lymphoid cells consist of immune system cells such as B and T lymphocytes, dendritic cells and macrophages, and the fibroblast-like reticular cells that produce the supporting stroma.

Lymphoid tissues are connective tissues that house lymphocytes and provide a site for their proliferation and maturation.

Lymphoid tissues can be diffuse, loosely packed arrangements of lymphoid cells and reticular fibers, or they can be solid egg-shaped structures with densely packed lymphoid cells and reticular fibers called nodules or follicles.

Lymphoid nodules, widely scattered around the mucus membranes lining the respiratory, digestive, reproductive, and urinary systems, are called mucosa-associated lymphatic tissues or MALT.

At some places, like along the gastrointestinal or respiratory tracts, MALT can become aggregated and form clusters, such as the tonsils in the pharynx walls and Peyer's patches in the intestinal wall.

These aggregated nodules are strategically located to avoid the entry of microbes.