PLACENTAL PROTEIN 14 INHIBITS IL-1β AND TNFα mRNA EXPRESSION IN PHA-STIMULATED HUMAN PBMC.

Abstract

208 Placental protein 14 (PP14) is a member of the lipocalin family, a group of soluble proteins with diverse functions. Predominately a secretory product of human decidua, PP14 is also found in follicular fluid, seminal fluid, the late secretory phase of endometrium, and platelets. Even though PP14 is most abundant in first trimester human amniotic fluid (80-125 mg/L) and is thought to participate in fetal tolerance, little information exists about the function of this protein. Previous investigations have demonstrated that PP14 purified from human decidual extracts inhibits mixed lymphocyte cultures and IL-1β and IL-2 secretion from phytohemagglutinin (PHA)-stimulated peripheral blood mononuclear cells (PBMC). Since IL-1β and TNFα are pivotal mediators in amplifying the immune response, we examined the ability of PP14 to inhibit human PBMC IL-1β and TNFα mRNA expression using Northern blot analysis. In these studies, human amniotic fluid was used as a rich source of PP14. PBMC were stimulated with PHA in the presence of amniotic fluid or amniotic fluid depleted of PP14 by immunoprecipitation. After 20 hours, RNA was isolated from these cells and probed for IL-1β, TNFα, and TGFβ1 mRNA expression. The Northern blot results show a dramatic increase in both IL-1β and TNFα expression upon PHA stimulation whereas amniotic fluid PP14 inhibits IL-1β and TNFα mRNA expression in a dose-dependent fashion. When we used non-saturating amounts of amniotic fluid depleted of PP14 by immunoprecipitation, the inhibition of IL-1β and TNFα mRNA expression was reversed. In contrast, amniotic fluid PP14 has no effect on the mRNA expression of TGFβ1, a known anti-inflammatory cytokine. In summary, amniotic fluid PP14 inhibits IL-1β and TNFα mRNA expression in PHA-stimulated PBMC. By inhibiting the expression of these pro-inflammatory cytokines, PP14, a naturally occurring immunosuppressive protein, has the potential of being a powerful therapeutic agent in the management of both acute and chronic allograft rejection.