State of the immune system in patients after a transfer of COVID-19 infection

It is known that manifestations of the post- COVID syndrome, while maintaining an imbalance in immunological parameters, can be observed for 6 or more months after a COVID-19 infection. Further study of the state of the immune system in the post-COVID and post-vaccination period is an urgent problem for understanding the mechanisms of immune defense, developing immunorehabilitation programs for post- COVID syndrome, creating new approaches to developing programs for the rehabilitation treatment of patients who have undergone COVID-19. The aim of this study was to assess the parameters of cellular and humoral immunity in the post-COVID period. Materials and methods. The parameters of cellular and humoral immunity were assessed in 126 patients (27 men and 99 women) who had COVID-19 infection, aged 25 to 83 years, within a period of 1 month to 1 year after the disease. The level of specific anti-SARS-CoV-2 IgG antibodies was also investigated by a quantitative enzyme-linked immunosorbent assay using the test system «SARS-CoV-2-IgG-IFA-BEST» (Russia). Results. Data were obtained indicating a long-term preservation of disturbances in the functional state of the immune system in the post-COVID period: an increased amount of T-regulatory cells (CD4+CD25+), T-lymphocytes with markers of late activation (CD3+HLA-DR+), medium and low molecular weight circulating immune complexes and decrease in the level of immunoglobulin A in the blood serum. Temporary aggravation of immune response disturbances was noted in subjects who undergone COVID-19, in the period of 3-6 months from the moment of clinical recovery. In addition, there were more pronounced changes in the immune system in individuals of the older age group. Differences in the level of specific anti- SARS-CoV-2 IgG antibodies in patients after COVID-19 infection depending on vaccination have been established.