Human leukocyte antigen–DR isotype (major histocompatibility complex class II) expression in different types of endometriosis

BACKGROUND: Disorders of the immune system, which regulates adhesion, invasion, proliferation, apoptosis, and neoangiogenesis, are essential in the development of endometriosis. At the same time, a significant role is assigned to the immunogenetic aspects of the progression of endometriosis, in particular, the influence of major histocompatibility complex, or human leukocyte antigens, on the regulation of the immune system in this disease. However, characteristic features of its expression in different types of endometriosis are poorly understood. AIM: The aim of this study was to determine the human leukocyte antigen–DR isotype (major histocompatibility complex class II) (HLA-DR) expression characteristics in endometrioid heterotopias in different types of endometriosis such as adenomyosis, endometrial ovarian cysts, and extragenital endometriosis. METHODS: This retrospective study was performed based on morphological and immunohistochemical studies of surgical material. The latter was carried out using the standard avidin-biotin complex method using mouse monoclonal antibodies specific to HLA-DR (class II). RESULTS: The study included 329 women aged 18 to 47 years who underwent surgical interventions for endometriosis of various organ localizations: 98 cases of internal genital endometriosis (adenomyosis), 196 cases of endometrial ovarian cysts, and 35 cases of extragenital endometriosis (21 cases of postoperative scar endometriosis and 14 cases of endometriosis of various parts of the intestine). Regardless of the organ localization of endometriosis, a clear pattern of HLA-DR (class II) expression was found. HLA-DR positive cells were found in the stroma of adenomyosis foci, in the capsules of endometrial ovarian cysts, and in extragenital heterotopias. They were more common in postoperative scar endometriosis—79 [75; 104], intestinal endometriosis—55 [50; 59], adenomyosis—56 [32; 97], and in endometrial ovarian cysts, their expression value was 14 [10; 63]. The glandular epithelium in endometrial heterotopias with signs of proliferation or secretion was HLA-DR negative in all the studied types of endometriosis—in adenomyosis, postoperative scar endometriosis, and intestinal endometriosis. Positive HLA-DR (class II) expression was found only in the epithelial lining of cystically transformed glands in adenomyosis foci and extragenital sites of endometriosis. The largest number of HLA-DR positive epithelial cells was found in the epithelial lining of endometrial ovarian cysts, the expression intensity being weak in 12.3%, intermediate in 72.3%, and strong in 15.4% of cases. CONCLUSION: The data obtained suggest that the HLA-DR positive phenotype of endometriosis may reflect a specific morphogenesis and abnormalities in the cell genome associated with chronic inflammation, which is important in the prognosis of the clinical course of the disease. Further comprehensive clinical, morphological, and molecular genetic studies are required.