Granulated lymphocytes with an unusual antigenic phenotype (CD56+ CD38+ CD2 +/- CD3- CD16-) form a substantial proportion of leukocytes in human endometrial stroma. The purpose of this study was to examine morphological and antigenic heterogeneity in endometrial granulated lymphocytes (eGL) in imprint preparations, paraffin-embedded sections and frozen sections. eGL in decidual imprints showed variations in cell size, nuclear size, shape and chromatin content and the number and size of cytoplasmic granules. eGL were detected in paraffin-embedded sections using phloxine tartrazine, alcian blue and toluidine blue stains. There was no difference in the number of eGL among the three stains but the granules appeared smaller and more regular when stained with toluidine blue. The proportion of stromal cells which were leukocytes increased from 8.2% in proliferative endometrium to 31.7% in early pregnancy decidua. The number of CD56+ and CD38+ cells increased in late secretory endometrium; CD56+ cells formed greater than 75% of the leukocytes in first trimester decidua. The increased number of CD2+ cells in decidua was not comparable with CD56+ and CD38+ cells suggesting that a lower proportion of CD56+ cells in first trimester decidua coexpress CD2, an observation which was supported by double labelling studies. eGL therefore show morphological and antigenic heterogeneity and the study of granulated lymphocytes in pathological endometrium and decidua will require careful phenotypic and morphological analysis of accurately dated samples.
Endometrial stromal granulocytes (EGs) are prominent in late luteal phase human endometrium and in early pregnancy decidua. They have been believed to develop from endometrial stromal cells and to secrete relaxin. Recent immunohistochemical studies have suggested that EGs are derived from bone marrow but this has been difficult to prove, mainly because the characteristic cytoplasmic granules are not preserved in frozen tissues. Two separate approaches have now been employed to investigate the cellular lineage of EGs. Formalin-fixed paraffin-embedded sections of first trimester decidua were labelled by an immunoperoxidase method with four monoclonal antibodies (mAbs) reactive with routinely fixed and processed tissues. In addition, acetone-fixed smears of decidual cell suspensions were labelled with a panel of mAbs. Sections and smears were counterstained to demonstrate the characteristic cytoplasmic granules of EGs. Endometrial granulocytes were LCA+, CD2+, MT1+, and UCHL1+, which provides evidence that they are leucocytes. EGs are probably members of the large granular lymphocytes series and may have an essential role in normal implantation and placentation.
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