CD4 and COVID-19: Although percentages of most cell subsets were restored to the levels of controls at the time of CP donation (ca. 2 months after recovery), specific alterations were observed in the levels of CD4+ (lower) and CD8+ (higher) T cells in CP donors who developed Abs and recovered from mild (non-hospitalized) or severe (hospitalized) COVID-19 (60.11% and 60.75%, respectively, compared to 71.36% of controls for CD4+, p < 0.01; 33.49% in both groups compared to 24.38% of controls for CD8+, p < 0.05).