Immunophenotyping of leukocytes in bovine placenta

Lymphocytes and macrophages are the main white cells involved in fetal-maternal tolerance. Little is known about these leukocytes in bovine placenta, such as the quantity and location of these cells. Thus, the objective of this study was to identify lymphocyte and macrophage populations in bovine placenta using specific markers and flow cytometry. This study analyzed samples of placentomes and intercaruncular regions of cows in the three quarters of pregnancy. In the placentomes, during the first quarter of pregnancy, mean percentage of labeled CD3+ cells was 2.34%; CD8+, 1.28%; CD14+, 1.66%; and CD335+, 0.96%. For the intercaruncular region, percentage of CD3+ cells was 0.71%; CD8+, 1.63%; CD14+, 2.81%; and CD335+, 2.81%. In the second quarter, placentomes showed 0.94% CD3+ cells; 0.77% CD8+; 0.72% CD14+; and 0.51% CD335+. In the intercaruncular region, percentage of labeled CD3+ cells was 0.50%; CD8+, 1.81%; CD14+, 2.64%; and CD335+, 0.51%. In the third quarter, placentomes showed labeling of 0.88% CD3+; 0.66% CD8+; 1.06% CD14+; and 0.74% CD335+ cells. In the intercaruncular region, percentage of labeled CD3+ cells was 0.19%; CD8+, 2.23%; CD14+, 2.43%; and CD335+, 0.16%. The results showed that there was a greater immunomarking of leukocytes CD3+ and CD335+ in the placentome when compared to the intercaruncular region during the third trimester. It can be concluded that leukocytes populations in bovine placenta is reduced, probably because of the syndesmochorial characteristic of bovine placenta. This represents a significant barrier for the immunological system of the mother, sharply decreasing the exposure of the conceptus to the mother’s immune system.