Differential Effects of Interleukin‐2 and Interleukin‐7 on the Induction of CD4 and CD8 Expression by Double‐Negative Human Thymocytes*

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Abstract
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 CD8 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.