Fig. 6: Effector CD4+ and CD8+ T-cell responses to SARS-CoV-2 S peptides following 7 day in vitro stimulation.

a Lymphocytes were identified by scatter characteristics and doublet exclusion (singlet lymphocytes) then T cells identified as CD3+ lymphocytes and subsets distinguished by either CD4 or CD8 expression. Bivariate analysis identified subsets of CD4+ T cells (top panel) and CD8+ T cells (bottom panel) producing TNF-α, IFN-γ and IL-2 after restimulation at day 7 and background signals from non-restimulated cells were subtracted. Percentages of IFN-γ+ CD8+ and CD4+ T cells are shown for sequential samples obtained after infection, PV1 and PV2 for b, c asymptomatic/mild (n = 6) and d, e moderate/severe (n = 11) groups. P values, calculated using Friedman’s test with Dunn’s multiple comparisons test, are shown above lines spanning the comparison groups when significant. Red lines bisecting groups represent median (solid) with IQR (dotted).