Immunology: Bone marrow-derived cell populations in uterine and ectopic endometrium

Uterine endometrium contains numerous bone marrow-derived cells.The spectrum of cell types is different from that of any othertissue, and the differences in endometrium from women with endometriosismay reflect a different endometrial phenotype in these women.The cell types of bone marrow origin found in ectopic endometriummay indicate the degree of differentiation of the tissue. Itwas found that, in normal endometrium, the CD45⁺ cell populationcomprised T cells, macrophages, CD56⁺ large granular lymphocytes,some CD16⁺ cells and a few B cells. Changes in these cell populationsduring the menstrual cycle were similar in endometrium fromboth controls and patients with endometriosis, and resembledthat reported previously by others. In ectopic endometrium,the frequency of CD45⁺ cells remained within the same rangeas that of uterine endometrium but without any obvious patternof change during the menstrual cycle. CD56⁺ large granular lymphocytes,an immune cell type characteristic of uterine endometrium, werealso found in ectopic endometrium. Our results indicate thatectopic endometrium, as well as comprising both glandular andstromal cells, contains bone marrow-derived cell populationssimilar to those of uterine endometrium. This suggests thatthe same processes of cell migration and/or differentiationoccur in ectopic and uterine endometrium.