Anti-Thy-1-mediated T cell activation. Role of soluble factors and expression of interleukin 2 receptors on T cells.

Rabbit anti-Thy-1 antibody bound to T cells induces the appearance of T cell growth factor (interleukin 2, IL2) receptors and the production of IL2. IL2 receptors induction by this means occurs within a short time span, and independent of any demonstrable accessory cell. A source of exogenous or endogenous IL2 is apparently the only requirement for proliferation after these receptors are expressed. IL2 production, on the other hand, is accessory cell-dependent, and this help is mediated via Fc receptors on the accessory cell. IL2 production in this model is demonstrable at 4-6 h, or earlier, and is proliferation-independent. X-irradiation actually augments apparent IL2 production. The data are consistent with the hypothesis that a differentiated subset of T cells in any mixed population is responsible for IL2 production.