Phenotypic and Functional Characteristics of Early Thymic Emigrants in Peripheral Blood in Normal Conditions and Autoimmune Diseases

Complex mechanisms of thymus functioning affect the structural matrix, contributing to the gradual accumulation of genetic mutations, changes in gene expression and premature immunosenescence. The study of early thymic migrants (RTE) is necessary to identify possible diagnostic biomarkers and potential checkpoints of autoimmune diseases. The object of the study were peripheral blood samples of patients with rheumatoid arthritis (RA), psoriatic arthritis (PsA), psoriasis (PS) and healthy donors. The aim of the study was to assess the ratio of recently migrated cells from the thymus and naive T-regulatory cells in the periphery in health and autoimmune pathology. The relative number of recent thymic migrants CD4+CD45RA+CD31+ (RTE) and the number of Foxp3+ T-regulatory cells (Treg) among them were determined by flow cytofluorimetry. The number of proliferating cells was determined by the intracellular Ki-67 content. The analysis showed that the number of RTE was reduced in the group of patients with RA and patients with PsA relative to the donor group (17.3%, 18.6% vs. 23.6%) and did not change significantly in patients with psoriasis. There were no significant differences between donors and patients with AID in the number of proliferating RTE and Tregs. The level of proliferation of T-regulatory cells in patients with psoriatic pathology was comparable to donor values, and in RA there was a tendency to an increase. In patients with RA, the number of proliferating naive Foxp3+ Tregs was significantly higher than the number of proliferating RTE (15.8% vs 3.1%, p0.05, respectively). A decrease in the relative number of RTE in AID may be associated with the activation of T lymphocytes and an increase in the proportion of central memory T cells. The number of Tregs among RTE and the level of their proliferation in patients with psoriatic pathology, indicate the absence of disturbances in the generation of T-reg in the thymus. The ambiguous results obtained in patients with RA, require additional confirmation on a larger sample of patients.