IP-10 shows homology to PF-4 (platelet factor-4) and belongs to the family of chemotactic cytokines known as chemokines. The receptor for IP-10 is CXCR3. IP-10 has been shown to bind to the virus-encoded viroceptor M3. The expression of IP-10 from a variety of cells, including monocytes, endothelial cells, keratinocytes, and fibroblasts, is induced by IFN-gamma and TNF-alpha. Human neutrophils produce IP-10 in response to IFN- gamma in combination with either TNF-alpha or bacterial lipopolysaccharides. IP-10 probably also plays a role in regulation of the growth of immature hematopoietic progenitor cells. It has been shown to suppress in vitro colony formation of highly enriched cells expressing the cell surface marker CD34 in the presence of SCF, GM-CSF, or SCF and EPO, but not in their absence with the exception of SCF.