Progesterone Induced Blocking Factor (PIBF) Mediates Progesterone Induced Suppression of Decidual Lymphocyte Cytotoxicity

Laškarin G, Tokmadžić VS, Štrbo N, Bogović T, Szekeres‐Bartho J, Randić L, Podack ER, Rukavina D. Progesterone induced blocking factor (PIBF) mediates progesterone induced suppression of decidual lymphocyte cytotoxicity. AJRI 2002; 48:201–209 © Blackwell Munksgaard, 2002 PROBLEM: Progesterone induced blocking factor (PIBF) is a mediator of progesterone that blocks peripheral blood lytic natural killer (NK) activity. Progesterone or PIBF stimulated decidual macrophages block up‐regulation of perforin expression in decidual lymphocytes (DL). Therefore, we investigated whether progesterone regulates cytotoxicity of DL. METHOD OD STUDY: Decidual mononuclear cells were cultured with progesterone, PIBF, progesterone and anti‐PIBF antibody or in the medium only. Cytolytic activity of non‐adherent DL was measured by PKH‐26 (red) 2 hr cytolytic assay and flow cytometry. Perforin positive DL were detected by immunofluorescency and PIBF‐positive cells by immunohistology. RESULTS: Progesterone and PIBF, in a dose‐dependent manner decreased cytotoxicity of DL against K‐562 targets, and perforin egzocytosys was blocked. Anti‐PIBF antibodies reversed the progesterone mediated reduction in cytolytic activity of DL. PIBF positive cells were found in first trimester pregnancy decidua. CONCLUSION: The results indicate possible role for PIBF, as a mediator of progesterone in regulation of DL cytolytic activity at the maternal–foetal (M–F) interface.