Effect of the immunoregulatory cytokines on successful pregnancy depends upon the control of graft rejection mechanisms

Successful outcomes in allopregnant women depend upon control of graft rejection mechanisms. An understanding of how the fetus escapes the maternal immune system may be relevant for the prevention of transplant rejection. It has been suggested that the same immunosuppressive cytokines contribute to successful pregnancy and transplantation. Recent reports suggest a role for transforming growth factor beta (TGF-beta) in the generation of T-regulatory lymphocytes. In contrast, production of proinflammatory cytokines accompanying intrauterine infection has been associated with fetal rejection or preterm labor. Interleukin-12 (IL-12) is the unique stimulator for differentiation of T-helper lymphocytes (Th) to Th1 cells. It rapidly induces transcription of Th1 cytokines such as interferon-gamma. This study was performed in 70 pregnant women at 21 to 36 weeks gestation, and in 32 healthy nonpregnant controls. An indirect enzyme-linked immunosorbent assay was used to estimate TGF-beta 1, and IL-12 in serum. The results showed that TGF-beta 1 levels were higher in all pregnant women compared with the nonpregnant controls. No significant changes in serum levels of IL-12 were observed in pregnant compared with the normal control women. The results suggested that the cytokine milieu of the placenta appeared to play a critical role in the maternal acceptance of the fetus, and that TGF-beta 1 may function as a regulatory factor in fetal allograft survival during pregnancy.