Understanding the benign nature of SIV infection in natural hosts
J. Clin. Invest. Guido Silvestri, et al. 117:3148 doi:10.1172/JCI33034 [Go to this article.]

Figure 2
Dynamics of the CD4⁺ T cell pools during pathogenic and nonpathogenic lentiviral infections. This figure represents the changes induced by HIV/SIV infection in the size of the pools of naive (Tn, blue), memory (Tcm, pink), and effector (Tem, red) CD4⁺ T cell subsets in both peripheral blood (PB) and MALT. The top row shows how HIV infection is associated with rapid decline of the mucosal CD4⁺ T cells and much slower, but eventually very severe, depletion of the circulating pool of CD4⁺ cells (this latter event is associated with progression to AIDS). The middle row shows how nonpathogenic SIV infection of SMs is associated, in approximately 90% of cases, with preservation of the peripheral pool of CD4⁺ T cells but a rapid depletion of the same cells in mucosal tissues. The bottom row shows how a minority of SIV-infected SMs experience a severe depletion of CD4⁺ T cells in both peripheral blood and MALT — and yet do not exhibit any clinical signs of AIDS. The term “CD4-low” refers to the small subset (~3%–5%) of SIV-infected SMs with CD4⁺ T cell counts below 200 cells/mm².