Loss of CD161⁺⁺/MAIT cells in HIV infection. Isolated PBMCs from healthy controls (n = 23) and patients with early (n = 35) or chronic stage HIV infection (n = 13) were stained for CD161 expression on CD8⁺ T cells. (A) There was a lower frequency of CD161⁺⁺ cells in early and chronic HIV infection compared with the healthy control cohort, with no differences seen in the CD161⁺ populations. Results are displayed as a proportion of the CD8⁺ T cell population. (B) Representative FACS plots showing differences in the frequency of CD161⁺⁺CD8⁺ T cells. Plots are gated on CD3⁺ cells. (C-D) PBMCs from the healthy control and chronic HIV infection cohorts were stimulated with PMA/ionomycin as described in “Methods.” The CD8⁺ T cells were analyzed for production of IFNγ, IL17A, and IL22. The gating strategy is shown in supplemental Figure 9a. (C) Representative FACS plots of PMA and ionomycin stimulated PBMCs in HIV⁺ patients and healthy subjects. Plots are gated on CD8⁺ T cells. (D) There were lower frequencies of IL17A producing cells in the HIV⁺ patients but no difference in the frequency of IFNγ or IL22 producing cells. Note data points lie on the x-axis (values of 0% were arbitrarily ascribed a value of 0.001% so as to appear on the log scale).