HIV infection is characterized by progressive T-cell depletion. T-cell depletion increases the production of both apoptosis stimulating fragment (FAS) and interleukin-7 (IL-7). As shown by Rethi et al, IL-7 synergizes with FAS to induce proliferation of suboptimally activated T cells. It is known that chronic hyperactivation/proliferation induces T-cell apoptosis and death, particularly of bystander cells. The whole process results in T-cell depletion, thus completing the HIV-AIDS pathogenesis cycle. Professional illustration by Alice Y. Chen.