Distribution of the T cell element of the immune system in post-COVID patients with first identified hyperglycemia

Post-COVID syndrome combines many adverse outcomes with often new-onset conditions, including type 2 diabetes mellitus (DM). The relevance of the study is the insufficient data on T cell immunity in patients with hyperglycemia after COVID-19. The purpose of this study was to identify the characteristics of T cell immunity in individuals with post-COVID syndrome and newly diagnosed carbohydrate metabolism disorders (CDM) in the post-COVID period. The study included 100 patients (32 men and 68 women) aged from 38 to 70 years (mean age (M±m) was 59.40±8.80 years) with a verified post-COVID-19 condition. All patients were divided into three groups: group 1 – patients with concomitant newly diagnosed impaired glucose tolerance (IGT) in the post-COVID period (prior to SARS-CoV-2 infection, no increase in glycemia was detected according to primary medical documentation) (n = 30), group 2 – patients with concomitant newly diagnosed type 2 diabetes mellitus (n = 30), and group 3 – patients with the development of post-COVID syndrome without hyperglycemia (n = 40). During the study, the following parameters were determined: CD45⁺, CD3⁺ (T lymphocytes), CD45⁺, CD3⁺, CD4⁺ (helper inducers), CD45⁺, CD3⁺, CD8⁺ (cytotoxic T lymphocytes), CD45⁺, CD3⁺, CD4⁺, CD25⁺, CD127^- (T regulatory cells), CD45⁺, CD3⁺, CD4⁺, CD25⁺ (T lymphocytes – early activation), CD45⁺, CD3⁺, HLA-DR⁺ (T lymphocytes – late activation). Infection with SARS-CoV-2 with the subsequent development of post-COVID syndrome and persistent hyperglycemia (IGT, type 2 diabetes) in the post-COVID period was accompanied by a higher level of the total number of T lymphocytes. A study of the T lymphocyte population revealed changes in the subpopulation composition. In the group of patients with CDM, a significant increase in T cytotoxic and T regulatory cells was noted. More pronounced changes in the subpopulation composition were identified in the group of patients with newly diagnosed type 2 diabetes in the post-COVID period: an increase in the relative and absolute numbers of T helper cells and T cells of late activation of lymphocytes. Disorders of carbohydrate metabolism associated with COVID-19 are accompanied by changes in the subpopulation composition of T lymphocytes. In individuals with newly diagnosed type 2 diabetes in the post-COVID period, hyperactivation of the T cell component of the immune system was revealed. Heterogeneous data were obtained in individuals with newly diagnosed impaired glucose tolerance, which requires further study of this group of patients.