Human members of a family of structurally related cytokines, which play a role as effectors of inflammation, were analyzed for their expression and regulation in T lymphocytes. Members of this gene family include Platelet Basic Protein (PBP); Platelet Factor 4 (PF-4); IL-8/NAP-1; IP-10, a gamma interferon induced protein; GRO; pAT 464 and pAT 744. In resting T lymphocytes the RNAs of the individual genes could not be detected, but all genes were induced upon stimulation with PHA or with PHA/PMA. The induction of five genes was blocked by the immunosuppresive drug cyclosporin A (CSA), which appears to affect initial events in T cell activation. This expression in T lymphocytes, especially the sensitivity to CSA, indicates a common immunmodulatory role of these structural related proteins.