To characterize the biologic activities of potential mediators of allergic inflammation, we have cloned, expressed, and purified guinea pig RANTES (gpRANTES). cDNA for gpRANTES was cloned from Con A-stimulated guinea pig spleen cells. A high level of gpRANTES expression in Escherichia coli was achieved by mutation of a human RANTES (hRANTES) expression construct to obtain a 68-amino acid protein identical with the predicted guinea pig amino acid sequence, assuming an equivalent amino terminus as the human protein. Purified gpRANTES was an effective stimulus of human eosinophils as assessed by increases in intracellular free calcium in fura-2-loaded cells and chemotactic responses in vitro. gpRANTES exhibits similar potency and efficacy to hRANTES. In marked contrast, neither gpRANTES nor hRANTES was able to activate guinea pig peritoneal eosinophils in these assays, even in the presence of IL-5. However, gpRANTES was found to be a potent stimulator of guinea pig peritoneal macrophages. Following tracheal instillation of gpRANTES, a dose-dependent increase in macrophages, but not eosinophils, was observed in gpBAL. Macrophage accumulation was detectable by 6 h and sustained for at least 48 h. These results indicate that RANTES in the guinea pig may have a different cellular selectivity than that described in the human, which may be important in the use of animal models in the analysis of allergic disorders. These selectivities do not appear to be accounted for by differences in guinea pig and human RANTES sequences.