Cytokines are small proteins that have an essential role in the immune and inflammatory responses. The repertoire of cytokines is becoming diverse and expanding. Here we report the identification and characterization of a novel cytokine designated as chemokine-like factor 1 (CKLF1). The full-length cDNA of CKLF1 is 530bp long and a single open reading frame encoding 99 amino acid residues. CKLF1 bears no significant similarity to any other known cytokine in its amino acid sequence. Expression of CKLF1 can be partly inhibited by interleukin 10 in PHA-stimulated U937 cells. Recombinant CKLF1 is a potent chemoattractant for neutrophils, monocytes and lymphocytes; moreover, it can stimulate the proliferation of murine skeletal muscle cells. These results suggest that CKLF1 might have important roles in inflammation and in the regeneration of skeletal muscle.
Abbreviations used: ANAE, acid α-naphthyl acetate esterase; CKLF, chemokine-like factor; EGFP, enhanced green fluorescent protein; EST, expressed sequence tag; HE, haematoxylin–eosin; IL-10, interleukin 10; PHA, phytohaemagglutinin; POX, peroxidase; RT–PCR, reverse-transcriptase-mediated PCR; SSH, suppression–subtractive hybridization; STCP-1, stimulated T-cell chemotactic protein 1; TARC, thymus and activation-regulated chemokine.