The Age-Dependent Role of Th22, Tc22, and Tc17 Cells in the Severity of Pneumonia in COVID-19 Immunopathogenesis

Coronavirus disease 2019 (COVID-19) has clinical manifestations ranging from mild symptoms to respiratory failure, septic shock, and multi-organ failure. Lymphocytes are divided into different subtypes based on their cytokine production pattern. In this study, we investigated the role of cytokine expressions of CD4 + T (T helper [Th]1, Th2, Th17, Th22) and CD8 + T cell subtypes (T cytotoxic [Tc]1, Tc2, Tc17, Tc22) in the pathogenesis of COVID-19. Peripheral blood mononuclear cells (PBMCs) were extracted with Ficoll by density gradient centrifugation from blood samples of 180 COVID-19 patients (children and adults) and 30 healthy controls. PBMCs were stimulated with PMA and Ionomycin and treated with Brefeldin A in the fourth hour, and a 10-colored monoclonal antibody panel was evaluated at the end of the sixth hour using flow cytometry. According to our findings, the numbers of Th22 (CD3 + , CD4 + , and interleukin [IL]-22 + ) and Tc22 (CD3 + , CD8 + , IL-22 + ) cells increased in adult patients regardless of the level of pneumonia (mild, severe, or symptom-free) as compared with healthy controls ( p