Fig. 2: Blood MAIT cells are activated and secrete proinflammatory cytokines in patients with COVID-19.

a, Representative quantile contour plots of CD69, CD56 and double-positive surface marker expression on blood MAIT cells from one uninfected control and two patients with COVID-19 who were admitted to an IDU and an ICU, respectively. CD69⁺, CD56⁺ and CD56⁺CD69⁺ MAIT cell frequencies in the blood of uninfected controls (n = 80) and infected patients from the IDU (n = 62) and ICU (n = 66). b,c, MDS plot (b) and UMAP (c). c, Analysis of MAIT cells for each uninfected (n = 23) and infected patient from the IDU (n = 50) or ICU (n = 66) from Bichat hospital analyzed with the same flow cytometer. d, UMAP divided by groups and colored by the scaled expression of CD69 and CD56. e,f, Representative quantile contour plots and frequencies of IFN-γ (e) and GzB (f) in MAIT cells after stimulation from uninfected controls (n = 25–27) and patients with COVID-19 hospitalized in an IDU (n = 14–15) or ICU (n = 15). g, Representative quantile contour plots and frequencies of GzB⁺ MAIT cells without stimulation in uninfected controls (n = 19) and patients in an IDU (n = 11) or ICU (n = 14) with COVID-19. h, Comparative analysis of frequencies of GzB⁺ MAIT cells without stimulation in blood and ETAs of patients in an ICU with COVID-19 (n = 7). Representative quantile contour plots are shown on the left, and individuals are shown on the right. Small horizontal lines indicate the median and quartiles (a) or the median (e–g). Each symbol represents one biological sample. *P < 0.05, **P < 0.01, ***P < 0.001 and ****P < 0.0001 (two-sided Mann–Whitney non-parametric test (a and e–g) and Wilcoxon signed-rank test (h)).