Cell-specific expression of B lymphocyte (APRIL, BLyS)- and Th2 (CD30L/CD153)-promoting tumor necrosis factor superfamily ligands in human placentas.

Apoptosis-inducing tumor necrosis factor (TNF) ligands and receptors have been reported in human placentas, but the expression patterns of family members lacking this function [a proliferation-inducing ligand (APRIL), B lymphocyte stimulator (BLyS), CD30L/CD153, CD40L/CD154, TNF-related activation-induced cytokine, CD27L/CD70, OX40L, activation-inducible TNF receptor ligand (AITRL)] are incompletely documented or unknown. We therefore investigated expression of these eight ligands and nine of their receptors (B cell maturation antigen, transmembrane activator and calcium-modulator and cyclophilin ligand-interactor, CD30, CD40, receptor activator of nuclear factor-kappaB, osteoprotegerin, CD27, OX40/CD134, AITR). Analysis by reverse transcriptase-polymerase chain reaction revealed mRNAs encoding only three of the ligands (APRIL, BLyS, CD30L/CD153). Immunoblots demonstrated all three proteins in first-trimester and term placentas, and immunohistochemical experiments showed that expression was cell-specific and gestation-related. Although mRNAs encoding receptors for the three expressed ligands were absent, those encoding receptors for all of the unexpressed ligands were detectable. Collectively, the results are consistent with the postulate that nonapoptosis-inducing, placenta-derived TNF superfamily cytokines contribute to the T helper cell type 2 bias required for successful pregnancy. Patterns of placental expression of receptors suggest bidirectional maternal-fetal cytokine communication.