The effect of human placental protein 14 (PP14) on the production of interleukin-1 from mitogenically stimulated mononuclear cell cultures.

Crude human decidual tissue extracts containing placental protein 14 (PP14) were shown to inhibit the production of interleukin-1 beta (IL-1) from mitogenically stimulated mononuclear cell cultures. The inhibition was dose-dependent over the range of PP14 concentrations investigated (0-8.0 mg/l) and was effective on both phytohaemagglutinin-(PHA) and lipopolysaccharide- (LPS)-induced IL-1 secretion. Using these culture systems, a PP14 concentration of 1.0 mg/l induced a 34% suppression of IL-1 secretion following LPS stimulation and 22% following PHA stimulation. For PHA stimulation the suppression of IL-1 secretion was effective throughout the culture period investigated (0-89 hr). Individual crude decidual extracts inhibited the incorporation of [3H]thymidine into PHA-stimulated lymphocytes, such inhibition being partially reversed by the addition of exogenous recombinant IL-1 to the cultures. These results suggest that the previously reported immunosuppressive activity of PP14 may be mediated by the suppression of IL-1 secretion.