Interactions of humoral immune response indicators and parameters of systemic inflammatory response in patients with post-COVID-19 syndrome

   Objective. To assess the state of the systemic inflammatory response and humoral immune response in middle-aged patients came through COVID-19 infection in mild and moderate severity.   Materials and methods. A cohort single-center study involving 83 patients came through COVID-19 infection in mild and moderate severity (women - 69.9% (58 patients), men - 30.1% (25 patients); median age 53 years [49; 56] was conducted over the period 2022-2023. All patients underwent clinical examination, evaluation of humoral response with determination of IgG and IgM antibodies to SARS-CoV-2 virus, as well as concentration of interleukins: interleukin-1β, interleukin-4, interleukin-6, interleukin-8, interleukin-10, high-sensitivity C-reactive protein, tumour necrosis factor α, transforming growth factor β1 and procalcitonin concentrations. Patients were divided into three groups: 1-3 months; 3-6 months; and 6 months to 1 year after COVID-19 infection.   Results. Within a year the percentage of IgM-positive patients in all patient groups was about a quarter (25 %, 21 % and 25 % respectively). While remaining within the reference values for the whole group, procalcitonin and interleukin-10 levels in the selected cohort exceeded those of the test-negative cohort (p = 0.0053 and p = 0.0044, respectively), which we considered as persistent chronic compensated inflammation.   Conclusion. A quarter of patients who came through COVID-19 infection in mild and moderate severity have persistently positive IgM levels for a year, combined with proinflammatory status according to systemic inflammatory response parameters.