Progesterone-induced blocking factor 1 (PIBF1) (PIBF1)

Progesterone-induced blocking factor 1 (PIBF1) is a multifunctional protein that plays a critical role in the immunological maintenance of pregnancy and cellular organization. Primarily induced by progesterone in lymphocytes and trophoblast cells, PIBF1 is secreted to modulate the maternal immune system by shifting the cytokine balance toward a Th2-dominant profile and inhibiting natural killer (NK) cell activity [1, 4]. This immunomodulatory function is essential for preventing the rejection of the semi-allogeneic fetus. Beyond its role in reproduction, PIBF1 also functions as a centrosomal protein (also known as CEP90) that is vital for spindle assembly, microtubule organization, and ciliogenesis [2]. In clinical settings, low levels of PIBF are associated with recurrent miscarriage and preterm birth, while its overexpression is frequently observed in various cancers, where it promotes tumor cell proliferation and immune evasion [1, 5]. Pharmacological management often involves the use of progesterone or dydrogesterone to induce PIBF expression in threatened pregnancies, whereas its inhibition is a subject of interest in oncology [1, 6].

Other names

PIBFCEP90Centrosomal protein of 90 kDa

Progesterone-induced expression of PIBF1 leads to the secretion of a 34 kDa immunomodulatory protein that binds to a receptor complex composed of IL-4Rα and a PIBF-specific chain (PIBF-R). This interaction activates the STAT6 signaling pathway, which induces the production of Th2 cytokines (e.g., IL-4, IL-10) and suppresses the cytolytic activity of natural killer (NK) cells, thereby creating an environment conducive to pregnancy maintenance [1, 5, 6].