Profile of cytokine mRNA expression in peri-implantation human endometrium

The human embryo and subsequent fetus is a semi-allograft and immunologically foreign to the mother. Successful embryonic implantation and maintenance of normal pregnancy depends on intricate interactions between the invading embryo, maternal endometrium and maternal-immune response. Cytokines are pivotal in determining the type of maternal T-helper immune response, which can be divided into T-helper 1 (TH1)-mediated delayed hypersensitivity and T-helper 2 (TH2)-mediated humoral immunity. We examined the pattern of TH1 [interleukin (IL)-2, IL-12 and interferon-gamma] and TH2 (IL-4 and IL-6) cytokine expression in the peri-implantation endometrium of 10 fertile, multiparous women. Endometrial samples were timed to the mid-cycle luteinizing hormone (LH) surge, with collection on days LH+7 to LH+9. Analysis for cytokine mRNA was by mRNA extraction and reverse transcription-polymerase chain reaction. The results show a lack of TH1 and predominant TH2 cytokine expression. We postulate that endometrial cytokines may contribute to the local modulation of maternal adaptive immune response in peri-implantation endometrium, to facilitate successful embryonic implantation and maintenance of pregnancy.