The expression of human leukocyte antigens class I and II in women with endometriosis or adenomyosis

Objectives. The human leukocyte antigen (HLA) system has been implicated in the aetiology of endometriosis. We aimed to compare the HLA class I and II expression in endometrial specimens from women with endometriosis or adenomyosis. Methods. We studied the HLA class I and II expression in endometrial specimens from 16 women with endometriosis and 15 with adenomyosis which were compared with 15 specimens from women without endometriosis or adenomyosis. Immunohistochemistry was performed using mouse antihuman IgG2a monoclonal antibody for HLA I and IgG1 for HLA II. Results. Women with endometriosis had significantly higher HLA I and II expression in stroma (100% and 87.5% vs. 66.7% and 40%, p < 0.02 and p = 0.007, respectively) and glands (87.5% and 56.3% vs. 46.7% and 20%, p < 0.02 and p = 0.04, respectively) compared to controls, while in the adenomyosis group the expression of HLA I was comparable with controls and the HLA II expression was increased in stromal cells (73.3% vs. 40%, p = 0.03) and decreased in glands (6.6% vs. 20%, p = NS). Conclusion. Women with endometriosis had a significantly higher expression of HLA molecules whereas in adenomyosis there was a tendency of lower expression of these molecules. This could explain the suppression of cellular immunity in the peritoneal cavity.