Immunohistochemical characterization of leucocyte subpopulations in endometriotic lesions

Leucocyte subpopulations localized in endometriotic lesions were analysed using the avidin-biotin immunoperoxidase technique on 15 biopsies obtained by CO2 laser excision. Qualitative assessment of the leucocyte subpopulations was performed with a panel of antihuman monoclonal antibodies for leucocytes (anti-Hle-1), T-lymphocytes (anti-leu-4), T helper/inducer (anti-leu-3a), T suppressor/cytotoxic (anti-leu-2a), B cells (anti-leu-12), HLA-DR (anti-HLA-DR), macrophages (anti-leu-M3) and natural killer cells (anti-leu-7, anti-leu-11; anti-leu-19). Leucocyte common antigen (anti-Hle-1)-positive cells were present in all lesions and were the most frequent stromal leucocytes. Of these, the T lymphocytes are the most frequent subpopulation together with the macrophages. The CD4/CD8 ratio was 0.78. No anti-leu-7 and/or anti-leu-11-positive cells were found although a substantial amount of anti-leu-19-positive cells were found in each lesion. There were very few B cells present in the ectopic endometrial lesions. In conclusion, an important amount of cytotoxic lymphocytes (anti-leu-2a -and anti-leu-19-positive cells) and macrophages (anti-leu-M3) were found in the endometriotic lesions. The possible importance of these intraendometriotic leucocytes for the pathophysiology of endometriosis will be discussed.