Investigation of IL-6 serum level in COVID-19 patients with positive COVID-19 IgG/IgM antibody titers to check inflammation and disease progression

Objective: The SARS-CoV-2, the cause of coronavirus disease 2019 (COVID-19), leads to severe pathogenicity and high mortality among different communities around the world. Therefore, it is important to understand the mechanisms of virus pathogenesis and the immune system's response to prevent the further spread of this virus. This study was aimed to evaluate the relationship between the serum level of interleukin 6 and positive IgG and IgM antibody levels in patients with COVID-19 to investigate inflammation and disease progression. Methods & Materials: In this study, 10 ml of EDTA blood samples were taken from 414 COVID-19 patients. Then, the plasma was separated and the levels of IgM and IgG antibodies and interleukin 6 cytokine were evaluated by ELISA and chemiluminescence methods, respectively. All data were analyzed by SPSS 22 and GraphPad prism 9 software at the significance level of P < 0.05. Results: The results of this study showed that there was no significant difference in the expression of IgM and IgG antibodies between men and women. Also, a significant increase in the mean expression of IL -6 was observed only in the high concentration range (100- 1000 pg/ml) in men compared to women (P < 0.001). In addition, in the female population, all three concentration ranges (negative, medium, and high) of IL -6 have the highest correlation with high titers (>10 U/ml) of IgM and IgG antibodies. While, in men, all three concentration ranges of IL -6 had the highest correlation with > 10 U/ml IgM antibody titers, but in the case of IgG, the highest correlation between different concentrations of IL -6 was observed with the negative or moderate titers of this antibody and there was an inverse relationship with the high titers of IgG (>10 U/ml). Conclusion: As a result, the relationship between different serum levels of cytokine IL -6 with different titers of IgM and IgG antibodies was observed in both male and female populations. In general, it can be concluded that the correlation between different concentrations of IL -6 with different IgM titers was similar in both men and women, but in the case of different IgG titers, this correlation was higher in women than men.