IMMUNE CORRELATES OF POST-COVID SYNDROME AT VARIOUS GLUCOCORTICOID LEVELS

Introduction: Long-term sequelae of COVID-19 include disturbances in the immune and endocrine systems. Of particular interest is the role of cortisol as a key stress response hormone, potentially affecting the restoration of immune homeostasis in patients with post-COVID syndrome. Changes in the regulation of the hypothalamic-pituitary-adrenal axis can form various immune phenotypes that complicate the body's adaptation after infection.

Objective: To assess the parameters of the immune system in patients with post-COVID syndrome depending on the blood cortisol level, with an emphasis on natural killers, T-lymphocytes and platelet indices.

Materials and methods: 109 patients who had COVID-19 at least 6 months ago were examined. The level of cortisol in the morning serum was used to stratify patients into three groups: with normal, elevated and reduced values. The immune status was assessed by flow cytometry. The levels of NK cells, T lymphocytes and their subpopulations (helpers, cytotoxic) were analyzed - both by CD45+ and CD46+ panleukocyte markers, as well as general blood test parameters, including the average platelet volume. Statistical data processing was performed using nonparametric methods.

Results: Patients with low cortisol levels showed a significant decrease in both the absolute and relative number of NK cells, as well as a decrease in the average platelet volume. In this group, an increase in the number of T lymphocytes was simultaneously observed. In patients with hypercortisolemia, a decrease in the level of T cytotoxic cells was recorded. Immune differences clearly correlated with the level of cortisol. Conclusions: The obtained data demonstrate the presence of at least two immune phenotypes in post-COVID patients: one associated with hypercortisolemia and decreased cytotoxic T cells, the other with hypocortisolemia, NK cell deficiency and platelet activity. These differences highlight the need to take into account the hormonal status when assessing and treating post-COVID conditions.

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