Characterization of lymphocyte subpopulations and T cell activation in endometriosis

Numerous studies have characterized the lymphocyte subpopulations in normal eutopic endometrium and suggested a role for the cytokine secretory products of these lymphocytes in regulating endometrial cell proliferation and differentiation. Recent studies have shown that ectopic endometrium contains a greater concentration of scattered stromal lymphocytes than does eutopic endometrium. However, the lymphocyte subpopulations and their activation status have not been characterized in ectopic endometrium.

We performed immunohistochemical studies on serial sections of proliferative and secretory phase eutopic endometrium and ectopic endometrium obtained during the proliferative phase using monoclonal antibodies to CD4 (T helper-inducer cells), CD8 (T cytolytic-suppressor cells), CD22 (B-cells), CD56 (natural killer cells), and VLA-1 (T-cell activation marker).

Ectopic endometrium contained significantly more scattered stromal CD4, CD8, and activated T cells than did proliferative and secretory eutopic endometrium. There were more activated T-cells in proliferative than in secretory eutopic endometrium. Ectopic endometrium contained significantly fewer NK cells than proliferative and secretory endometrium.

These results demonstrate that (1) the increased lymphocyte population in ectopic endometrium is due to increased numbers of CD4 and CD8 cells, and (2) a greater number of activated T cells are present in ectopic endometrium as compared to eutopic endometrium. Increased concentration of stromal T cells and enhanced VLA-1 expression in ectopic endometrium suggest that cytokine products of the activated T-cells may be involved in regulating cellular processes of endometriosis tissue.