Molecular cloning and characterization of a novel CXC chemokine macrophageinflammatory protein-2 gamma chemoattractant for human neutrophils and dendritic cells

Chemokines play important roles in leukocyte trafficking as well as functio n regulation. In this study, we described the identification and characteri zation of a novel CXC chemokine from a human dendritic cell (DC) cDNA libra ry, the full-length cDNA of which contains an open reading frame encoding 1 11 aa with a putative signal peptide of 34 aa, This CXC chemokine shares gr eatest homology with macrophage inflammatory protein (MIP)-2 alpha beta, he nce is designated as MIP-2 gamma, mouse MIP-2 gamma was identified by elect rocloning and is highly homologous to human MIP-2 gamma, Northern blotting revealed that MIP-2 gamma was constitutively and widely expressed in most n ormal tissues with the greatest expression in kidney, but undetectable in m ost tumor cell lines except THP-1 cells. In situ hybridization analysis dem onstrated that MIP-2 gamma was mainly expressed by the epithelium of tubule s in the kidney and hepatocytes in the liver, Although no detectable expres sion was observed in freshly isolated or PMA-treated monocytes, RT-PCR anal ysis revealed MIP-2 gamma expression by monocyte-derived DC. Recombinant MI P-2 gamma front 293 cells is about 9.5 kDa in size and specifically detecta ble by its polyclonal Ab developed by the immunization with its 6His-tagged fusion protein. The eukaryotically expressed MIP-2 gamma is a potent chemo attractant for neutrophils, and weaker for DC, but inactive to monocytes, N K cells, and T and B lymphocytes. Receptor binding assays showed that MIP-2 gamma does not bind to CXCR2, This implies that DC might contribute to the innate immunity through the production of neutrophil-attracting chemokines and extends the knowledge about the regulation of DC migration.