CXCR3 and HIV infectious disease: Based on the findings that there is increased expression of CXCR3 that is associated with enhanced monocyte transmigration in the brains of HIV-infected patients and SIV+ infected macaques, we next sought to examine the effect of HIV Tat (as a surrogate of HIV infection) on the expression of CXCR3 in human monocytes in vitro.