severity of covid-19 infectious and immune-based profile

Background: severe acute respiratory syndrome coronavirus 2 (sars-cov-2) causes immune system dysregulation and a systemic cytokine storm. under healthy conditions, t helper cells protect against intracellular pathogens, extracellular parasites, and extracellular bacteria. objectives: for the novelty of our study, little is known regarding the balance of t cell subtypes and responses in two forms of covid-19 in our country. we investigated whether there was a relationship between t cell subtype frequency and cytokines by covid-19 severity. methods: forty-six pcr-confirmed severe (n = 30) and moderate (n = 16) covid-19 patients and 13 sex- and age-matched healthy control (hc) subjects were enrolled. immunophenotyping of t cell subsets and related serum cytokines was performed using flow cytometry and elisa, respectively. results: there was a significantly lower frequency of cd8+tbet+ (p < 0.01) t cells in the severe group compared to hc. also, there was a significantly lower frequency of cd4+gata3+ (p < 0.001) and cd8+tbet+ (p < 0.001) t cells in the severe group compared to the moderate group. moreover, receiver-operating characteristic (roc) curve analysis revealed a considerable correlation between ctl (cd8+t-bet+) subtypes and the severity of the disease. severe covid-19 disease was associated with reduced interferon-gamma (ifn-γ) and interleukin (il)-2 concentration and increased il-5 and il-6 concentration. conclusions: reduced systemic levels of il-2 can trigger decreased numbers of th1 and th2 cells, and in contrast to elevated il-5 and il-6, the numbers of th2 cells did not increase in these cases.