Identification and characterization of a novel beta chemokine containing six conserved cysteines

The chemokines are emerging as a diverse and expanding family of cytokines. In this study, we report the identification of a novel beta (CC) chemokine that exhibits an unusual pattern of six conserved cysteines and was thus designated 6Ckine. The primary amino acid sequence of 6Ckine is highly conserved in humans, mice, and pigs and contains the expected four cysteines characteristic of the beta chemokine family plus two additional carboxyl-terminal cysteines. Expression of human 6Ckine appears to be restricted to lymphoid organs, particularly lymph node, spleen, and appendix, while murine 6Ckine has a broader tissue distribution with the highest mRNA levels found in spleen and lung. Recombinant murine 6Ckine was chemotactic in vitro for thymocytes and activated T cells, but not for B cells, macrophages, or neutrophils. Together these data demonstrate that 6Ckine is a novel member of the chemokine superfamily.