Characterization of endometriosis-associated immune cell infiltrates (EMaICI)

Objective: To identify and characterize endometriosis-associated immune cell infiltrates (EMaICI). Furthermore, to define occurrence and size of EMaICI in various types of endometriosis. Methods: Immune cells were characterized in samples of 60 premenopausal women with histological proven endometriosis. Therefore, immunohistochemical staining with monoclonal antibodies for CD3, CD4, CD8, CD45RO, CD25, CD56, CD68, and CD20 on sections of paraffin-embedded endometriotic tissue was performed. Results: EMaICI were observed in all the types of endometriosis, and characterized as T lymphocytes (CD3+), helper T lymphocytes (CD4+), cytotoxic T lymphocytes (CD8+), antigen-experienced T lymphocytes”memory cells” (CD45RO+), macrophages (CD68+), and B lymphocytes (CD20+). The maximum frequency of EMaICI and their distribution per endometriotic lesion (EML) was observed in peritoneal endometriosis (pEM) and in ovarian endometriosis (Ov. EM). In myometrium from adenomyosis (M/AM), EMaICI occurrence was lower and smaller in size in comparison with EMaICI seen in other forms of endometriosis. EMaICI were negative for regulatory T cells (CD25+ high, FoxP3+) and natural killer cells (NK cells, CD56+). Conclusion: Numerous and brisk EMaICI comprising several types of immune cells in all endometriosis forms suggest acute immunological reactions within the microenvironment of endometriosis lesions.