Differentiation and cell division in the mammalian thymus

Abstract

The thymus is the primary differentiation site for T (thymus-derived) lymphocytes (Metcalf, 1966). Over the past 20 years, cell traffic to and from the thymus has been investigated, and the lymphocyte population of the thymus has been found to be composed of myriad phenotypically distinct subpopulations. Several recent reviews have treated these subjects in detail (e.g., Scollay and Shortman, 1983, 1985; Scollay et al, 1984a; Mathieson and Fowlkes, 1984; Fowlkes and Mathieson, 1985). This work has resulted in a wealth of information that allows T-cell development to be examined with high resolution. By this analysis, events in the thymus provide vivid and accessible examples of processes common to many developmental systems: specific homing and migration, formation of specific cell-cell contacts, mitogenesis, coordinate and noncoordinate gene activation, induction of gene rearrangements, and programmed cell death. In this review, current knowledge of the biology of the thymus serves as a framework to define the molecular events by which thymic precursor cells are endowed with the functional properties of mature T cells.

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