Responses of Helper T Cell Subsets at Diagnosis and After Discharge in Patients with Non-Severe COVID-19: A Prospective Observational Study.

Objective: Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the virus responsible for Coronavirus Disease 2019 (COVID-19), elicits a strong immune response similar to that seen in other viral infections. The predominant cell type in this immune response also influences the disease prognosis. This study, conducted between 2022 and May 2023, aimed to evaluate the transcription factors and cytokine expressions of Th (helper T) cell subsets at the time of diagnosis and after discharge in patients with non-severe COVID-19. Materials and Methods: Forty-eight patients with non-severe COVID-19 were included in the study. Transcription factor and cytokine expressions of Th cell subsets were evaluated using the quantitative polymerase chain reaction (qPCR) method, and the results were compared at the time of diagnosis and after discharge. Results: It was determined that the cytokines and transcription factors of T helper 1 (Th1) cells (T-box expressed in T cells [T-bet], 2.71-fold, p<0.001; Interferon-gamma [IFN-γ], 1.42-fold, p=0.010) and T helper 17 (Th17) cells (RAR-related orphan receptor gamma [RORγt], 1.06-fold, p=0.946; Interleukin-22 [IL-22], 1.01-fold, p=0.599) decreased, whereas the expression of T helper 2 (Th2) cells (GATA binding protein 3 [GATA3], 2.56-fold, p<0.001; Interleukin-4 [IL-4], 1.34-fold, p=0.012; Interleukin-5 [IL-5], 1.02-fold, p=0.649; Interleukin-13 [IL-13], 2.06-fold, p=0.0119) and regulatory T (Treg) cells (Forkhead box P3 [FoxP3], 3.56-fold, p<0.001; Transforming growth factor-beta [TGF-β], 1.03-fold, p=0.670; Interleukin-10 [IL-10], 1.40-fold, p=0.010) increased. Conclusion: Our study in non-severe COVID-19 patients demonstrated significant changes in the transcription factor and cytokine expressions of Th cell subsets at the time of diagnosis compared to discharge. We think that even if the patients do not exhibit severe clinical and laboratory findings, Th cell immune responses may be strong, warranting careful consideration.