CD4 and lymphopenia: Moreover, Hermens and Kesmir observed lymphopenia and a reduction in the numbers of CD4 and CD8 T-cells in COVID-19 patients, with severity correlating with the extent of these reductions.31 They also noted an increased proportion of activated CD38+ and HLA-DR+ cells in severe COVID-19 cases, suggesting a triad of factors: overactivation, exhaustion, and susceptibility to apoptosis.