MOLECULAR-CLONING AND FUNCTIONAL-CHARACTERIZATION OF A NOVEL CC-CHEMOKINE, STIMULATED T-CELL CHEMOTACTIC PROTEIN (STCP-1) THAT SPECIFICALLYACTS ON ACTIVATED T-LYMPHOCYTES

A novel human chemokine STCP-1 (stimulated T cell chemotactic protein) was isolated from an activated macrophage cDNA Library. The chemokine has four cysteines positioned in a manner that identifies STCP-1 as a member of the CC chemokine family. The amino acid sequence shows 34% identity with RANTES. The gene consists of 3 exons and 2 introns with the position of intron/exon boundaries similar to that of RANTES. The gene is expressed as a 3.4-kilobase transcript on lymph node, thymus, and appendix. STCP-1 induces Ca2+ mobilization in a small percentage o f primary activated T lymphocytes, but on repeated stimulation the per centage of T lymphocytes that respond to STCP-1 increases, The chemoki ne STCP-1 does not induce Ca2+ mobilization in monocytes, dendritic ce lls, neutrophils, eosinophils, lipopolysaccharide-activated B lymphocy tes, and freshly isolated resting T lymphocytes, Similarly, STCP-1, wh ile acting as a mild chemoattractant for primary activated T lymphocyt es, is a potent chemoattractant for chronically activated T lymphocyte s but has no chemoattractant activity for monocytes, neutrophils, eosi nophils, and resting T lymphocytes. As STCP-1 acts specifically on act ivated T lymphocytes, it may play a role in the trafficking of activat ed/effector T lympho- cytes to inflammatory sites and other aspects of activated T lymphocyte physiology.