HUMAN MIG CHEMOKINE - BIOCHEMICAL AND FUNCTIONAL-CHARACTERIZATION

Mig is a chemokine of the CXC subfamily that was discovered by differe ntial screening of a cDNA library prepared from lymphokine-activated m acrophages. The mig gene is inducible in macrophages and in other cell s in response to interferon (IFN)-gamma. We have transfected Chinese h amster ovary (CHO) cells with cDNA encoding human Mig and we have deri ved CHO cell lines from which we have purified recombinant human Mig ( rHuMig). rHuMig induced the transient elevation of [Ca2+](i) in human tumor-infiltrating T lymphocytes (TIL) and in cultured, activated huma n peripheral blood-derived lymphocytes. No responses were seen in huma n neutrophils, monocytes, or Epstein-Barr virus-transformed B lymphobl astoid cell lines. rHuMig was chemotactic for TIL by a modified Boyden chamber assay but rHuMig was not chemotactic for neutrophils or monoc ytes. The CHO cell lines, IFN-gamma-treated human peripheral-blood mon ocytes, and IFN-gamma-treated cells of the human monocytic cell Line T HP-1 all secreted multiple and identical HuMig species as revealed by SDS-PAGE. Using the CHO-derived rHuMig, we have shown that the species ' heterogeneity is due to proteolytic cleavage at basic carboxy-termin al residues, and that the proteolysis occurs before and not after rHuM ig secretion by the CHO cells. The major species of secreted rHuMig ra nged from 78 to 103 amino acids in length, the latter corresponding to the full-length secreted protein predicted from the HuMig cDNA. Carbo xy-terminal-truncated forms of rHuMig were of lower specific activity compared to full-length rHuMig in the calcium flux assay, and the trun cated species did not block the activity of the full-length species. I t is likely that HuMig plays a role in T cell trafficking and perhaps in other aspects of the physiology of activated T cells.