DIFFERENTIAL MESSENGER-RNA EXPRESSION OF 3 DISTINCT CLASSES OF FC-GAMMA RECEPTOR AT THE FETOMATERNAL INTERFACE

Heterogeneous expression of three classes of Fc-gamma receptor (Fc-gamma-RI, IIa, IIb, and III) in the human placenta and decidua was examined by Northern blot hybridization and cDNA amplification analysis by polymerase chain reaction. Messenger RNA of Fc-gamma-RI, IIa and III genes were consistently expressed in the human placenta in all trimesters of gestation. The transcripts of the Fc-gamma-RIIb gene, on the other hand, dramatically increased in placentae at the second and third trimesters. This characteristic expression of Fc-gamma-RIIb after 20 gestational weeks was confirmed by sequential cDNA amplification analysis. Fc-gamma-RI, IIa and III mRNAs, but not Fc-gamma-RIIb, were also detected in the human decidua. Interestingly, while Fc-gamma-R mRNA could be induced in uterine endometrium by pseudopregnancy therapy using estrogen and progesterone, there was no detectable mRNA in hormone-unprimed normal endometrium. These findings suggest that Fc-gamma-Rs expressed at the feto-maternal interface can be transcriptionally regulated by sex steroid hormones as multifunctional molecules. In addition, the Fc-gamma-RIIb molecule is predominantly produced by placental tissues after the mid-trimester of gestation and possibly plays an important role in the transport of IgG molecules from mother to fetus.