Therefore, HIV infection, but not TB, may enhance the ability of total and CD4lowCD8high DP T cells to increase apoptosis by increasing the secretion of granzyme A. Although granzyme A and perforin cooperate to induce target cell apoptosis (30), no differences in the percentage of perforin-producing DP T cells were observed in the HIV and HT group compared with the HC and TB group. This evidence concerns the gene PRF1 and tuberculosis.