Fig. 6: Tissue-resident memory CD8⁺ T cells are expanded post-COVID-19.

a,b, Unsupervised clustering of CD8⁺ T cells from adenoids and tonsils according to flow cytometric surface markers (a). Quantification of the effect of previous SARS-CoV-2 infection on CD8⁺ T cell clusters showing regression coefficients ± 95% CI and P values, estimated with a linear model controlling for age and sex (b). Significantly different clusters (P < 0.05) between post-COV and UC groups are indicated with a star or highlighted in red. Adenoids post-COV n = 12, UC n = 35; tonsils post-COV n = 15, UC n = 42. c, Frequency of CD57⁺PD-1⁺CD8⁺ T cells in post-COV and UC adenoids (post-COV n = 17, UC n = 42, P = 0.044) and tonsils (post-COV n = 18, UC n = 46, P = 0.030) d, Flow cytometry plots showing CD69, CD103, CXCR5 and CXCR3 expression on CD57⁺PD-1⁺CD8⁺ T cells from one tonsil, representative of tonsils and adenoids from 26 donors. e, Adenoid from post-COV donor showing the location of CD57⁺PD-1⁺CD8⁺ T in one GC, representative of six samples. GC is circled, magnification of square is in inset. CD8 is cyan, CD57 is yellow, PD-1 is pink. HLA-DR (blue) stains follicles and Ki-67 (red) stains GC. 1 indicates CD8⁺CD57⁺PD-1⁺; 2 indicates CD8⁺CD57⁺ cells. Scale bars, 50 μm (left) and 10 μm (right). f, Cytokine/cytotoxic factor combinations (involving granzyme B, IFN-γ, CD107a, IL-2 and TNF, analyzed by SPICE) produced by tonsillar CD8⁺ T cells from post-COV (n = 13) and UC (n = 13) donors following PMA and ionomycin stimulation (category 3, P = 0.049; 10, P = 0.051; 14, P = 0.035; 18, P = 0.020; 19, P = 0.032; 22, P = 0.007; 23, P = 0.001; 26, P = 0.017; 30, P = 0.025). Sample list for a–c is in Supplementary Table 2 and e,f in Supplementary Table 11. Each symbol represents one donor. Mean ± s.d. are displayed in bar plots. Significance calculated using two-sided Mann–Whitney U-test. *P < 0.05.

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