Fig 1: Loss of peripheral CD8+CD161hi T cell frequencies correlates with increased severity of COVID-19(A) Overview of groups in this study.(B) UMAP visualization of PBMC subsets identified by FlowSOM clustering. Samples from all participants were pooled and down-sampled to 3,000 live CD45+ cells per sample. MO, monocyte; NK, natural killer; DC, dendritic cell; PMN, polymorphonuclear neutrophil; Baso, basophil.(C) Representative marker expression by CD4+ T cell, CD8+ T cell, MO, NK cell, and B cell subsets.(D) Correlation analysis of immune cell subsets as shown in (C) with disease severity rank.(E) Expression of CD161, TCR ?d and CD56 in CD8+ T cell subsets. NK cells were used as a positive control for CD56 expression.(F) UMAP of samples grouped by disease severity rank. Samples collected within 3 days from initial symptom score recording were included.(G) Frequencies of CD161hi T cells (mean ± standard error) in different severity groups (left) and their correlation with severity rank (right).(H and I) Age comparisons among severity rank and between sexes.(J) Multiple linear regression of age (x1) and severity rank (x2) with CD161hi cell frequencies. Regression models with p values are shown for age and severity rank.Significance was determined by Kruskal-Wallis test with Dunn’s test (E) or ANOVA (H and I): *p < 0.05, **p < 0.01, ***p < 0.001. Correlation efficiency was calculated by Spearman’s rank correlation (D and G). See also Figure S1 and Tables 1 and S1.