Fig. 4.

T cells show a hyperactivated/exhausted phenotype during COVID-19 infection. Phenotype of circulating CD4⁺ and CD8⁺ T cells from healthy donor (HD) and SARS-Cov-2 infected patients (CoV-2). Frequencies and absolute numbers of circulating (a) CD4 and (b) CD8 T cells. c, d Expression of the CD69 activation marker and (e, f) of the TIM-3 checkpoint molecule on CD8⁺ and CD4⁺ T cells. g CXCR6-expressing CD8 T cells. e Intracellular Aiolos expression, expressed as Mean Fluorescence Intensity (MFI). Representative histogram of Aiolos expression on CD8 + T cells from a HD (blu line), Survived (green line) and Dead patients (red line). Middle bars represent medians. Full red symbols indicate deceased patients. The Mann–Whitney U test was used to compare the two groups. *p < 0.05, ***p < 0.001, ****p < 0.0001