Stability of cytokine and immunoglobulin concentrations in the general population: prepandemic basal concentrations and intraindividual changes until the COVID-19 pandemic

Abstract Background: Evidence on physiological, basal concentrations of cytokines in the general population across sociodemographic groups, and their stability, is scant. No studies have analyzed intraindividual changes in such concentrations from before the COVID-19 pandemic until its outbreak. Objectives: To investigate: a) prepandemic concentrations of cytokines and immunoglobulins to viral exposures in a general, non-institutionalized population, and their associated sociodemographic variables; b) the intraindividual change in such concentrations between a prepandemic period (2016-17) and the initial pandemic period (2020-21); and c) whether such change was similar in participants who in 2020-21 were SARS-CoV-2 seronegative and seropositive, and between participants who did and did not develop COVID-19. Methods: We conducted a prospective cohort study in 240 individuals from the general population of Barcelona, Spain. Thirty cytokines and 31 immunoglobulins were measured in paired serum samples collected in 2016-17 and 2020-21 in the same individuals. Results: The median value of the relative intraindividual change in cytokine concentrations between 2016 and 2020 was <15% for 29 of the 30 cytokines. A substantial number of participants had an intraindividual increase or decrease ≥15% in some cytokines. No major differences in intraindividual changes of cytokine and immunoglobulin levels between 2016 and 2020 were observed between participants participants who did and did not develop COVID-19. Conclusions: Intraindividual changes in cytokines and immunoglobulins during the four years were moderate, and were not affected by SARS-CoV-2 infection or COVID-19 disease. The findings are novel, and potentially useful in clinical practice and research.