The Maturation of Lymphoid Tissue Structure and Function in Ontogeny

Abstract

A number of structural organizations have been identified in the peripheral lymphoid tissues of man and animals. In encapsulated lymph nodes, these include a raore-or-less distinct division between cortex and medulla, the presence of primary lymphoid follicles and subsequently mature germinal centers, and a discrete interfollicular zone in the lymph node cortex. On a more functional basis, the lymph node has been divided geographically into “thymus-dependent regions”, concerned primarily with cellular immunologic events, and “bursa-dependent regions”, devoted presumably to the production of humoral antibody (1). The spleen is similarly, although less precisely, characterized by a white pulp and a red pulp, with germinal centers and their characteristic lymphocytic mantles prominent in the periarterial Malpighian bodies. Intense infiltrates of lymphocytes and plasma cells with or without germinal centers also characterize the wall of the intestinal tract, and here a special relationship has been postulated between the lymphoid germinal center and its superjacent epithelium (2). As was pointed out elsewhere in this symposium, however, all of the structural organizations and all of the functions normally attributed to organized lymphoid tissue may be duplicated at almost any other location within the body (3).