DIFFERENTIAL-EFFECTS OF INTERLEUKIN-7 AND INTERLEUKIN-2 ON T-CELL RECEPTOR GAMMA-DELTA-EXPRESSING CELLS WITHIN CD4(-)CD8(-) POSTNATAL HUMAN THYMOCYTES

Highly purified CD4(-)8(-) double-negative (DN) human thymocytes proliferated significantly more in response to interleukin (IL)-7 than to IL-2 in a dose-dependent fashion. Both IL-7 and IL-2 promoted the appearance of T-cell receptor (TCR) gamma delta-expressing cells in single cell suspension culture of DN thymocytes. While IL-7 exerted a vigorous growth-stimulating effect on TCR gamma delta-bearing DN thymocytes, IL-2 preferentially maintained the viability of gamma delta thymocytes without promoting their strong proliferation. In both instances, the major subset of gamma delta thymocytes expressed V delta 1 rather than V delta 2 as a variable delta-chain element on their surface. These results reveal differential effects of IL-7 and IL-2 on TCR gamma delta-bearing human thymocytes and underline the importance of both ILs in the development of DN thymocytes.