CCL5 or RANTES (acronym for Regulated upon Activation, Normal T cell Expressed and presumably Secreted), was initially discovered by subtractive hybridization as a transcript expressed in T cells but not B cells. Eosinophilchemotactic activities released by thrombinstimulated human platelets have also been purified and found to be identical to RANTES. Besides T cells and platelets, RANTES has been reported to be produced by renal tubular epithelium, synovial fibroblasts and selected tumor cells.