Recent studies have shown the important role of proinflammatory cytokines and chemokines in the pathogenesis of atherosclerosis and diabetes mellitus (DM). Interferon-inducible protein of 10 kD (IP-10/CXCL10), a member of the CXC chemokine superfamily, is a potent chemoattractant for activated T lymphocytes and is reported to be involved in various disease states including atheroma plaque formation, inhibition of tumor angiogenesis and maintenance of podocyte function. However, the involvement of IP-10 in type 2 DM, especially in its vascular and renal complications, is largely unknown. To elucidate the etiopathological role of IP-10 in type 2 DM, we measured the concentrations of IP-10 together with IFN-gamma, TNF-alpha, IL-18, IL-6 and MCP-1 in plasma samples from 103 type 2 DM patients with various degrees of nephropathy. A significant difference in the plasma level of IP-10 was observed between the patients and the control subjects (183.3+/-12.5 pg/m/vs 65.6+/-9.3 pg/ml, p< 0.05). IP-10 correlated IL-18, IL-6, TNF-alpha and MCP-1. The IFN-gamma level was below the detectable range. IP-10 levels became higher with the progression of nephropathy: IP-10 levels were 148.9+/-14.5, 174.2+/-17.2 and 231.9+/-31.3 pg/m/in patients with an urinary albumin creatinine ratio of< 30, 30 to 300 and> 300 microg/mg Cr, respectively. Similarly, IL-18, IL-6, MCP-1 and TNF-alpha levels in patients with overt albuminuria were significantly higher as compared with those without albuminuria (IL-18, 367.3 45.6 vs 203.5+/-17.6 pg/ml; IL-6, 1.61+/-0.26 vs 0.87+/-0.13 pg/ml; TNF-alpha, 1.83+/-0.48 vs 0.61+/-0.07 pg/ml; p< 0.05, respectively) in consistent with previous reports. These results suggested that IP-10 may have an etiopathogenic role in type2 DM and diabetic nephropathy as one of the downstream effectors of proinflammatory cytokines.