CD4 and HIV-1 infection: Consistent with what has been observed during the course of human HIV-1 infection, we also observed a dramatic reduction in CD4+ T cells in the SI IEL (M1 − M2 = 56 ± 8.0, t = 7.0, df = 6, p < 0.001), SI LPL (M1 − M2 = 40 ± 4.9, t = 8.3, df = 6, p < 0.001), LI IEL (M1 − M2 = 23 ± 5.3, t = 4.3, df = 6, p = 0.005), and LI LPL (M1 − M2 = 49 ± 9.3, t = 5.2, df = 6, p = 0.002) (Figure 5A and 5B).