Placental protein 14 (PP14) inhibits the synthesis of interleukin-2 and the release of soluble interleukin-2 receptors from phytohaemagglutinin-stimulated lymphocytes.

Crude human decidual extracts containing up to 15.0 mg/l PP14 were investigated for their effects on the release of interleukin-2 (IL-2) and of IL-2 receptor (IL-2R) from phytohaemagglutinin (PHA) stimulated lymphocytes. The crude decidual extract suppressed IL-2 production over the culture period investigated (0-90 h) with maximal suppression observed at around 66 h of culture. The suppression was dose dependent over the range of PP14 concentrations used (0-7.0 mg/l). Decidual extracts also inhibited the release of soluble IL-2R into the culture supernatants over the same period. In both cases, the specific reduction of the PP14 content of the extracts by a monoclonal anti-PP14 immunoadsorbent reduced the observed suppression. These results suggest that PP14 inhibits the production of IL-2 from mitogenically stimulated lymphocytes, and leads to a reduced IL-2R release. The mechanism for such an effect is as yet unknown; however, it may explain the previously reported immunosuppressive activity of PP14.