One of the best-known functions of TGFB1 is that of immunoregulation, but during pregnancy, TGFB1 has been suggested to play a role in several other processes, including implantation, trophoblast differentiation, and in the activation and resolution phases of angiogenesis [11, 12] . The recognized importance of TGFB1 during the angiogenic process has been strengthened by its ability to regulate the vascular endothelial growth factor (VEGF) family, which includes VEGFs A, B, C, and D as well as placental growth factor (PGF) [13] [14] [15] [16] . Therefore, we hypothesized that PSGs may induce TGFB1 to promote immune tolerance, affect trophoblast function, and promote angiogenesis in the pregnant uterus. We explored this possibility by examining the effect of PSG1 in cell types involved with development of the placental blood supply, including primary monocyte/macrophages, low-passage primary endothelial cells, and two extravillous trophoblast cell lines.