Endometrial lymphoid tissue in the timed endometrial biopsy: Morphometric and immunohistochemical aspects

OBJECTIVES: The purpose of this study was to provide a morphometric profile of endometrial granulated lymphocytes and to investigate qualitative and quantitative differences in leukocyte subsets in precisely timed luteal phase endometrial biopsies. STUDY DESIGN: Endometrial biopsies were obtained from 24 normal fertile women at 4, 7, 10, and 13 days after the luteinizing hormone surge. Endometrial granulated lymphocytes were assessed morphometrically in 2 μm resin sections. Eleven monoclonal antibodies were used to characterize leukocytes in frozen sections. Semiquantitation was performed with a Quantimet 970 image analyzer. Data were analyzed with one-way analysis of variance. RESULTS: CD8+ (T suppressor-cytotoxic) cells increased significantly from 4 to 7 days after the luteinizing hormone surge, whereas CD68+ macrophages increased from days 10 to 13. Lymphocytes with an unusual phenotype (CD56+, CD38+, CD2+) increased dramatically after 7 days. The volume fraction of endometrium occupied by the nuclei of endometrial granulated lymphocytes did not alter, but their mean nuclear diameter and axial ratio decreased from days 7 to 13. CONCLUSION: The morphometric findings indicate in situ proliferation of endometrial granulated lymphocytes rather than migration from the peripheral circulation. T lymphocytes, macrophages, and endometrial granulated lymphocytes increase significantly between certain stages of the luteal phase.