CXCR4 and infection: These modeling results might indicate partial impact of the direct infection of CD34+CD7+ cells with HIV-1 (Figure 5C) (84), and hence raise questions regarding additional molecular mechanisms underlying the loss (differentiation or death) of CD34+CD7+CXCR4+ cells, such as the Notch signaling pathway, SDF-1/CXCR4 signaling pathway, or inflammatory signals as described above.