• human leukocyte antigen-E;
  • JEG-3;
  • progesterone;
  • trophoblast

Problem  Among class Ib human leukocyte antigen (HLA) molecules, HLA-E is known to be a major ligand of CD94/NKG2 receptor on natural killer (NK) cells, and to play a pivotal role in recognition of extravillous trophoblasts (EVTs) by maternal immune cells. However, it is scarcely known how HLA-E expression is regulated in EVTs.

Method of study  In this study, we investigated whether progesterone, an essential hormone in maintaining pregnancy, regulated HLA-E expression in EVT-like cell line, JEG-3. HLA-E mRNA amount in cultured JEG-3 cells was assessed by real-time PCR and cell-surface HLA-E protein was analyzed by flowcytometry.

Results  Real-time PCR showed 3.5-fold increase 1 hour after the addition of 1000 ng/ml progesterone. This response was dimished by the addition of RU486, an antagonist for progesterone receptor. Flowcytometry indicated that 1000 ng/ml progesterone slightly enhanced HLA-E expression on the surface of JEG-3.

Conclusion  These results suggest that progesterone up-regulates HLA-E expression in JEG-3 cells through the pathway mediated by progesterone receptor. Our findings might give a new insight into immunomodulatory function of progesterone at fetomaternal interface.