Increased CD95 (Fas) and PD-1 expression in peripheral blood T lymphocytes in COVID-19 patients.

A low count of CD4+ and CD8+ lymphocytes is a hallmark laboratory finding in the coronavirus disease 2019 (COVID-19). Using flow cytometry, we observed significantly higher CD95 (Fas) and PD-1 expression on both CD4+ T and CD8+ T cells in 42 COVID-19 patients when compared to controls. Higher CD95 expression in CD4+ cells correlated with lower CD4+ counts. A higher expression of CD95 in CD4+ and CD8+ lymphocytes correlated with a lower percentage of naive events. Our results might suggest a shift to antigen-activated T cells, expressing molecules increasing their propensity to apoptosis and exhaustion during COVID-19 infection.