Cytokines involved in the generation of cytolytic effector T lymphocytes

The differentiation of precursor, antigen-competent, T cells into effective helper and/or cytolytic cells involves a number of different steps that are signaled by soluble molecules termed cytokines. We demonstrate here that subsets of T cells, distinguished on the basis of their expression of cell-surface markers, CD4 and CD8, receive distinct signals for differentiation. The precursor T cells of a T-cell subset that is MHC class II-restricted are readily activated by signals provided by rIL-1, rIL-2, rIL-3, or IFN-gamma. The precursor T cells of the MHC class I-restricted T-cell subset, on the other hand, are not readily activated by signals provided by rIL-1, rIL-3, or IFN-gamma. Recombinant IL-2 apparently functions in a nonrestricted manner, in that it can provide growth signals to both MHC class I- and class II-restricted T cells.