CD70 EXPRESSION ON T-CELL SUBPOPULATIONS - STUDY OF NORMAL INDIVIDUALS AND PATIENTS WITH CHRONIC IMMUNE ACTIVATION

CD70, the ligand of CD27, is a member of the TNF family, which include s molecules essential in the regulation of lymphocyte growth and survi val. It is absent on resting lymphocytes but can be induced in vitro w ith activating stimuli. To extend information about its expression by different T-cell subpopulations, and its regulation in normal and path ologic conditions, highly purified T-cell subpopulations were studied: CD70 expression depended both on the activating stimulus and on the T -cell subset analyzed. PMA + Ionomycin induced CD70 on the large major ity of CD8(+) cells, but only on a minority of CD4(+) cells (P < 0.002 ), and among these, preferentially on the CD45R0(+) subset compared wi th the CD45RA(+). The presence of CD4(+) lymphocytes in cell cultures containing mixtures of. T-cell subsets inhibited CD70 expression on CD 8(+) cells. On the contrary, stimulation with allogeneic cells induced CD70 expression also on CD4(+) cells. Moreover, CD70 was found to be expressed by chronically in vivo activated T-cells. in conditions char acterized by allogeneic and autoimmune reactions. These data suggest a possible role of CD70 in the pathogenesis of immune dysregulation; in terestingly, this role may not be simply restricted to bind to, and si gnal through, CD27, since cross-linking of CD70 enhances the prolifera tive response induced by the stimuli used to elicit its expression. (C ) 1997 Elsevier Science B.V.