The role of peripheral blood CD4+CD45RA+ T cells and CD4+CD45RO+ T cells in evaluation of COVID-19 patients

<bold>Background:</bold> The role of CD4⁺ T cell subset changes in evaluation of the severity of COVID-19 in patients remains unclear. <bold>Aim:</bold> To explore the significance of CD4⁺CD45RA⁺ T cells and CD4⁺CD45RO⁺ T cells in the early detection of critical COVID-19 patients. <bold>Methods:</bold> Using a case-control approach, 147 patients treated at Shanghai General Hospital from December 10, 2022 to March 1, 2023 were selected during the COVID-19 pandemic. The patients were categorized into uninfected (12), moderate (30), severe (53) and critical (52). The clinical data of patients were collected and analyzed using logistic regression. <bold>Results:</bold> No significant differences were observed in age, body mass index, vaccination status, and prevalence of chronic diseases (e.g., diabetes, hypertension) among 4 groups. The lymphocyte count decreased with disease severity: from 1.37*10^9/L in the moderate group to 1.03*10^9/L in the severe group and 0.78*10^9/L in the critical group. Significant variations were observed in the critical group, with a remarkable increase in CD4⁺CD45RA⁺/CD4⁺ (34.42±12.83%) and a decrease in CD4⁺CD45RO⁺/CD4⁺ (61.62±13.83%), compared to others based on blood cell flow cytometry. Additionally, a decrease in the absolute number of CD4⁺CD45RO⁺ T cells was observed (0.12*10^9/L) in the critical group, but not in CD4⁺CD45RA⁺ T cells (0.07*10^9/L). Logistic regression analysis indicated that CD4⁺CD45RA⁺/CD4⁺ (OR = 1.060 (1.026,1.096)) and CD4⁺CD45RO⁺/CD4⁺ (OR = 0.948 (0.919,0.977)) were associated with critical condition. <bold>Conclusions:</bold> The ratio of CD4⁺CD45RA⁺ and CD4⁺CD45RO⁺ in CD4⁺ T cells may serve as an indicator for promptly evaluating critical condition during the the course of COVID-19.