The Regulation and Function of the CD4 Coreceptor During T Lymphocyte Development
The progression of thymocytes through sequential developmental stages is marked by an ordered pattern of expression of many different cell surface molecules (Kruisbeek 1993). Of these, the CD4 and CD8 glycoproteins are noteworthy because their differential expression defines the two major lineages of mature peripheral T cells (Swain 1983). Although mature cells express one molecule or the other, the large majority of immature thymocytes expresses both CD4 and CD8. These double positive (DP) cells are subjected to a stringent selection process which favors survival of the few cells that can interact productively with host MHC molecules (Hogquist et al. 1994; von Boehmer 1994). Down-regulation of either CD4 or CD8 accompanies positive selection and precedes the emergence of mature cells with distinct effector functions.
KeywordsDouble Positive Thymic Selection Thymocyte Development Double Positive Thymocyte Thymocyte Selection
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