CD4 and HIV infectious disease: Tregs accumulate at the sites of chronic HIV infection and play a direct role in the promotion of T‐cell exhaustion through production of IL‐10 that inhibits T‐cell proliferation.81 Aside from Tregs, multiple cell types contribute to IL‐10 production and patients with elevated plasma levels of IL‐10 correlate with rapid disease progression and impaired CD4 T‐cell help.