The increase in positive rate of CXCL10 mRNA release assay in HIV co-infection patients may be related to the high expression level of CXCL10 that was caused by the cascade amplification in signal pathway, and maybe there are other signal pathways involved in the release of CXCL10 but independent of IFN-γ signal pathway or CD4+ T cells. The gene discussed is CD4; the disease is coinfection.