Deviations in populations of peripheral blood mononuclear cells and endometrial macrophages in the cow during pregnancy

The presence of conceptus alloantigens necessitates changes in maternal immune function. Here, we used the cow to evaluate whether species with epitheliochorial placentation have changes in specific leukocyte populations during pregnancy similar to those reported in species with hemotropic placentae. At days 33-34 of pregnancy, there was no effect of pregnancy status on the number of cells positive for CD8, CD4, gamma delta T cell receptor, or the monocyte marker CD68 in the peripheral blood mononuclear cell (PBMC) population. There was, however, an increase in the proportion of CD4(+) cells that were positive for CD25. There was no effect of status on the proportion of PBMCs that were CD8(+) when comparing preparturient cows to nonpregnant cows. However, preparturient cows had an increased percentage of PBMCs that were gamma delta T cells and CD4(+)CD25(+) and a tendency for a lower percentage that were CD68(+) cells. Using immunolocalization with anti-CD68, it was found that pregnant cows had increased numbers of CD68+ cells in the endometrial stroma as early as days 54-100 of gestation; this increase persisted through the last time examined (day 240 of gestation). Cells positive for CD68 were also positive for another macrophage/monocyte marker, CD14. In conclusion, pregnancy in the cow is associated with changes in peripheral and endometrial leukocyte numbers, which are similar to patterns observed in other species.