Release of a transforming growth factor (TGF)-beta 2-related suppressor factor from postimplantation murine decidual tissue can be correlated with the detection of a subpopulation of cells containing RNA for TGF-beta 2.

Postimplantation murine decidual tissue from allopregnant C3H mice has been shown to release in vitro a potent immunosuppressive factor closely related to transforming growth factor (TGF)-beta 2 but slightly lower in apparent molecular weight. Decidual suppressor factor (DSF) activity was first detected in decidual tissue supernatant at day 9.5 of gestation and reached a plateau by day 10.5 to 12.5. By Northern analysis of decidual and placental tissue with a simian TGF-beta 2 probe, two characteristic TGF-beta 2 mRNA transcripts were detected in decidual tissue. In situ hybridization analysis of C3H implant sites, with the simian (pGEM-G1G2) TGF-beta 2 riboprobe, revealed a small population of TGF-beta 2+ cells localized to postimplantation decidua basalis and metrial gland cell area after day 8.5. On and before day 8.5, when DSF was not detectable, few TGF-beta 2 mRNA+ cells were detected. To test for TGF-beta release in situ, sections of uterine tissue were stained with antibody specific for TGF-beta 2, that identified DSF in Western blots. In postimplantation tissues (day 9.5, 12.5) patchy anti-TGF-beta 2 staining was seen over decidual tissue. Before day 9.5, slight and diffuse staining over decidual tissue was present with more marked staining of extradecidual tissue. Very little staining was noted over day 9.5 decidual tissue by using anti-TGF-beta 1 antibody as a control; however, some staining was seen over postimplantation fetal trophoblast and myometrial tissue. Fractionation of disaggregated postimplantation decidua by velocity sedimentation revealed that TGF-beta 2 mRNA+ cells were predominantly small and sedimented in the same fraction(s) as those cells previously shown to release DSF in vitro. Thus, the release of TGF-beta 2 related DSF correlates with the in situ detection of TGF-beta 2 mRNA and the in situ release of TGF-beta 2 peptide. These studies suggest that DSF may be a form of TGF-beta 2 released by a population of small lymphocytic decidual suppressor cells.