Figure 1. Two-phase model for depletion of mB_Act from circulation.

The model outlined here is based on data generated by Titanji et al. (3) and Peruchon et al. (9). During the early stages of SIV infection (2 weeks), mB_Act cells leave the blood to home to lymphoid tissues. At 12 weeks after SIV infection, mB_Act cells migrate from the lymphoid tissues and rebound in the blood of typical progressor macaques and, to a much lesser extent, in the blood of rapid progressors. This model implies that mB_Act in rapid progressors die through apoptosis in lymphoid tissues, according to a mechanism related to PD-1 signaling on B cells (see Figure 2).