BACKGROUND: Human African trypanosomiasis, caused by Trypanosoma brucei, involves an early hemolymphatic stage followed by a late encephalitic stage. METHODS: We studied the expression of chemokines with use of microarray and enzyme-linked immunosorbent assay in T. brucei brucei-infected mice and in patients with human African trypanosomiasis and examined their role in controlling brain accumulation of T cells and parasites. RESULTS: The messenger RNAs (mRNAs) encoding CXCR3 ligands CXCL9 and CXCL10 demonstrated the greatest increases among chemokines in brain specimens of infected mice, as determined by microarray. CXCL9 and CXCL10 mRNA accumulation was interferon (IFN)-gamma-dependent. Expression of CXCL10 was predominantly observed in astrocytes. Weight loss was registered in wild-type but not in CXCL10(-/-) and CXCR3(-/-) infected mice. Infected CXCL10(-/-) or CXCR3(-/-) mice demonstrated reduced accumulation of trypanosomes and T cells in the brain parenchyma but similar parasitemia levels, compared with wild-type mice. CXCL10 and IFN-gamma levels were increased in the cerebrospinal fluid of patients with late stage but not early stage human African trypanosomiasis. Levels of CXCL10 in patients with late stage human African trypanosomiasis were associated with somnolence, low body weight, and trypanosomes in the cerebrospinal fluid. CONCLUSION: IFN-gamma-dependent CXCL10 is critical for accumulation of T cells and trypanosomes in the brain during experimental African trypanosomiasis. Data suggest CXCL10 as a candidate marker for late stage human African trypanosomiasis.