Alternatively, since memory CD4+ T cells, the principal targets for HIV infection, normally experience periods of rapid expansion when cognate antigen is presented, followed by contraction by apoptosis in the absence of antigen (Figure 7B), misexpression of genes could reduce the cell’s sensitivity to proapoptotic signaling, which could provide a selective advantage by allowing preferential survival of the cells during the contraction phase. The gene discussed is CD4; the disease is HIV infectious disease.