DIFFERENTIAL-EFFECTS OF INTERLEUKIN-2 AND INTERLEUKIN-7 ON THE INDUCTION OF CD4 AND CD8 EXPRESSION BY DOUBLE-NEGATIVE HUMAN THYMOCYTES

Expression of cell surface CD4 (in the absence of CD3/T cell receptor) characterizes an early stage of intrathymic T cell development. Here, we investigated the appearance of CD4 and dos expression on highly purified CD4(-)8(-) double-negative human thymocytes in response to interleukin (IL)-7 and IL-2. While IL-7 preferentially promoted the appearance of CD4 single-positive and CD4(+)8(+) double-positive thymocytes, Il-2 primarily induced CD8 single-positive thymocytes. A significant fraction of CD4 single-positive cells generated from double-negative thymocytes via IL-7 lacked cell surface CD3 expression. In contrast, the majority of CD8 single-positive cells generated from double-negative thymocytes via IL-2 coexpressed CD3. We conclude that IL-7 and IL-2 exert differential effects on the differentiation of early human T cell progenitors.