Is SIV infection associated with CD4+ T-cell depletion?
The progression of HIV disease in humans is characterized by decreasing blood CD4+ T-cell counts and, during the asymptomatic phase, increasing CD8 counts. But while the total number of CD8 T cells in the body likely increases, the fall in CD4 counts is partly due to redistribution, that is, enhanced trapping of circulating cells in lymphoid tissues. Sopper and colleagues (page 1213) report a comprehensive quantitative study of the changes in lymphocyte numbers in the nonhuman primate model of HIV infection. This is fundamentally a cross-sectional necropsy analysis of total and proliferating (Ki-67+) CD4+ versus CD8+ T cells in a cohort of normal and SIV-infected rhesus macaques, with or without an “AIDS-defining” illness. Effort was made to count lymphocytes in samples from all reasonably accessible sites, weighing the total organ and the representative sample to calculate total numbers. The main finding is that CD4 cell numbers increased rather than decreased in asymptomatic disease,
