Phenotypic Analysis of Activation Antigens on Mitogen-stimulated T Cells Utilizing Monoclonal Antibodies

The development of hybridoma technology (1) coupled with the analytical and separation capabilities of fluorescence-activated cell sorting and in vitro techniques, to discriminate functional properties and interactions of isolated T cell subsets, led to an extensive classification of human lymphocytes into defined subsets (2–6). Studies directed toward dissecting and characterizing human T cells by cell surface determinants have identified functionally distinct T cell subsets (3,4). Antigen expression on these T cell subsets has been correlated with functional properties and the differentiation state of cells (3). Moreover, surface molecules have themselves a function as recognition elements in the cellular interaction. Indeed, the 20,000 mol. wt. T3 surface molecule was found recently to be associated with the T cell receptor structure for antigen on all T cells (7,8). In addition, T cells activated by mitogens, soluble antigens, and alloantigen express new activation surface antigens linked to the specific stimulus and the genetic program of the cells responding to this stimulus (9–16). Although in most cases the actual physiological role of these cell products is as yet unknown, they may be important as part of a network through which cell-cell signals are conveyed by activated subsets of T cells. Recently a functionally distinct surface antigen defined by anti-Tac antibody was demonstrated exclusively on activated and terminally differentiated T cells (16–18).