Increased Expression of Cell Surface Markers on Endometrial γδ T‐Cell Receptor+ Intraepithelial Lymphocytes Induced by the Local Presence of the Sheep Conceptus

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Abstract
PROBLEM: In sheep, γδ T-cell receptor (TCR)+ cells are a major lymphocyte subpopulation in the luminal epithelium of the uterine endometrium. During late pregnancy, this population of T cells increases in number and becomes more granulated. This study was performed to determine whether this apparent activation was induced by local effects of the conceptus or systemic effects of pregnancy. METHODS: The unilaterally-pregnant ewe, in which the conceptus is surgically confined to one uterine horn, was used to distinguish between systemic and local effects of pregnancy on function of endometrial γδ TCR+ intraepithelial lymphocytes. Lymphocytes collected from peripheral blood, and from the endometrial luminal epithelium of cyclic and unilaterally-pregnant ewes (day 140 of gestation) were analyzed by flow cytometry. RESULTS: As compared to γδ TCR+ lymphocytes in peripheral blood, γδ TCR+ intraepithelial lymphocytes from non-pregnant ewes had a lower percentage of cells staining positive for CD25, CD44, and L-selectin. There was no effect of pregnancy on the percentage of γδ TCR+ peripheral blood lymphocytes staining positive for CD25, CD44, CD29, or L-selectin. Similarly, the percentage of intraepithelial lymphocytes staining positive for these antigens was similar for cells collected from cyclic ewes and cells from the nonpregnant uterine horn of unilaterally-pregnant ewes. In contrast, there was a higher percentage of CD25, CD44, CD29, and L-selectin+ cells for γδ TCR+ intraepithelial lymphocytes from the conceptus-containing uterine horn of pregnant ewes than for γδ TCR+ intraepithelial lymphocytes from the endometrium of cyclic ewes or from the nonpregnant uterine horn of pregnant ewes. CONCLUSION: The local presence of the conceptus causes changes in cell surface marker expression on endometrial γδ TCR+ intraepithelial lymphocytes during pregnancy. These changes may reflect conceptus-induced activation of this population of cells.