IMPLICATION OF THE COMMON GAMMA-CHAIN OF THE IL-7 RECEPTOR IN INTRATHYMIC DEVELOPMENT OF PRO-T CELLS

The effects of IL-7 on the growth and differentiation of thymocytes we re analyzed using murine fetal thymus organ cultures (FTOC) in the pre sence of mAbs specific for the conventional IL-7 receptor (IL-7R) and for the common gamma (gamma c) chain. In FTOC, the development of CD4( -)CD8(-) double-negative thymocytes to CD4(+)CD8(+) double-positive (D P) and CD4(+) or CD8(+) single-positive (SP) cells was not completely blocked by adding these mAbs, although cell growth was reduced by the treatment. To define a developing stage sensitive to the mAbs, most im mature thymocytes, Pgp-1(+)c-kit(+) cells, were cultured in the 2-deox yguanosine treated fetal thymus. In the presence of both mAbs in the c ulture, neither DP nor SP thymocytes developed whereas either of the m Abs partially blocked their development. These results indicate that t he gamma c is involved in early T cell development as an indispensable subunit of the functional IL-7 receptor complex.