Endometriosis and Premature Ovarian Insufficiency: Immunological Alterations Reflecting Different Links in the Same Pathogenic Chain (New Original Data)

External genital endometriosis (EGE) and premature ovarian failure (POF) are among the most common and socially significant gynecological diseases, impairing patients' quality of life and forcing women to resort to assisted reproductive technology (ART) programs for infertility treatment. The immune system is recognized as a key player in the development of these pathologies. Objective. To conduct a comparative analysis of immune disorders in common forms of external genital endometriosis and premature ovarian failure and to identify characteristics common to these diseases. Material and methods. An immunological examination was conducted in 47 women with grades III-IV EGE, 46 women with POF, and 31 women in a comparison group undergoing surgical treatment in the gynecology department of the Department of Operative Gynecology and General Surgery of the V.I. Kulakov National Medical Research Center of Obstetrics, Gynecology and Perinatal Gynecology, Ministry of Health of the Russian Federation. Peripheral blood lymphocyte phenotyping was performed using flow cytometry, and the serum autoantibody profile (M, G) to endometrial antigens, steroid hormones, and steroidogenic enzymes was assessed using enzyme-linked immunosorbent assay. Results. A systemic clinical blood test revealed higher levels of all NK cell subsets, a high level of Th17 cells, and a low level of Tregs in patients with EGE, reflecting the prevalence of chronic processes. In contrast, patients with POF exhibit a predominantly enhanced Th1 response, mediating impaired steroidogenesis. The autoantibody profile in EGE is characterized by a predominance of antibodies (M, G) to tropomyosin-3, tropomodulin-3, α-enolase-1, and estradiol, whereas in POF, autoantibodies (G) to steroidogenic enzymes (aromatase, 20, 22-desmolase, 21-hydroxylase) predominate. Conclusion. Adaptive immune responses, reflecting the imperfections of central T-lymphocyte selection in patients with this pathology, determine complications associated with prolonged sterile inflammation, the development of autoimmune reactions, and the formation of a background that impedes reproductive function. The presence of a characteristic autoantibody profile in external genital endometriosis and premature ovarian failure opens the prospect of developing diagnostic antibody panels for more accurate early diagnosis and the identification of high-risk groups for these diseases.