CD4 and AIDS: As in previous studies [40], there was a dramatic reduction in the number CD4+ T cells and a corresponding increase in CD8+ T cell numbers in the colon of AIDS compared to HIV-negative IBD patients and healthy controls (CD4 counts: median of 13 vs. 72 vs. 63 cells/0.8 mm2, respectively; CD8 counts: median of 84 vs. 39 vs. 59 cells/0.8 mm2 respectively) (Fig. 1a and b).