reduction of complements c3 and c4 in saliva and serum of patients suffering sars-cov-2 infection

Background: the complement system plays a role in chronic immune activation during viral infections. objectives: this study aimed to evaluate the levels of saliva and serum complements c3 and c4 in coronavirus disease 2019 (covid-19) patients and healthy individuals. methods: this cross-sectional study included 36 severe and 22 critical covid-19 hospitalized patients and 22 healthy individuals. serum and unstimulated salivary c3 and c4 levels were assessed using the immunoturbidimetric method and analyzed using one-way analysis of variance (anova) with the student-newman-keuls test as a post hoc analysis. results: salivary c3 and c4 levels were significantly lower in patients with severe and critical covid-19 than in healthy individuals. there was no significant difference between the groups infected with severe and critical covid-19. serum c3 and c4 levels were lower in critical covid-19 patients than in healthy individuals; nevertheless, no significant difference was observed between severe covid-19 patients and healthy individuals. additionally, serum c4 levels were lower in critical covid-19 patients than in severe covid-19 patients. conclusions: it appears that serum and salivary c3 and c4 levels decrease in patients with covid-19 infection.