Evaluation of Lymphocyte Subtypes in COVID-19 Patients.

Although many aspects of the COVID-19 disease have not yet been clarified, dysregulation of the immune system may play a crucial role in the progression of the disease. In this study, the lymphocyte subsets were evaluated in patients with different severities of COVID-19. In this prospective study, the frequencies of peripheral lymphocyte subsets (CD3+, CD4+, and CD8+ T cells; CD19+ and CD20+ B cells; CD16+/CD56+ NK cells, and CD4+/CD25+/FOXP3+ regulatory T cells) were evaluated in 67 patients with confirmed COVID-19 on the first day of their admission. The mean age of patients was 51.3 ± 14.8 years. Thirty-two patients (47.8%) were classified as severe cases, and 11 (16.4%) were categorized as critical. The frequencies of blood lymphocytes, CD3+ cells, CD25+FOXP3+ T cells, and absolute count of CD3+ T cells, CD25+FOXP3+ T cells, CD4+ T cells, CD8+ T cells, and CD16+56+ lymphocytes were lower in more severe cases compared to the milder patients. The percentages of lymphocytes, T cells, and NK cells were significantly lower in the deceased patients. (p= 0.002 and p= 0.042, p=0.006, respectively). Findings of this cohort study demonstrated that the frequencies of CD4+, CD8+, CD25+FOXP3+ T cells, and NK cells differed in the severe cases of COVID-19. Moreover, lower frequency of T cells and NK cells could be predictors of mortality in these patients.