Because CCR5, CXCR4 and CD4 expression or differences in cell growth could affect HIV-1 infection, we compared CXCR4 and CD4 expression and cell growth of CCR5-/CR1, CCR5-/CR2 and CCR5-/CR3 cells with those of mock-transduced TZM.bl cells. The gene discussed is CD4; the disease is HIV-1 infection.