4Modulation of maturation and function of dendritic cells by female sex steroid hormones

Problem:  Pregnancy represents an exclusive situation in which the immune and the endocrine system cooperate to prevent rejection of the embryo by the maternal immune system. While immature dendritic cells (iDC) in the early pregnancy decidua presumably contribute to the establishment of peripheral tolerance, hormones like estradiol (E2), progesterone (Prog) and bHCG are candidates that could direct the differentiation of DCs into a tolerance-inducing phenotype.
Methods and Results:  To test this hypothesis we generated iDCs from peripheral-blood-monocytes and exposed them to E2, Prog, bHCG and Dexamethasone (Dex) as control. Surprisingly, E2, Prog and bHCG upregulated the expression of HLA-DR, CD 40, CD 83 and CD 86. Visualization of the F-actin cytoskeleton confirmed these observations. In contrast, the T-cell stimulatory capacity of DCs was reduced after E2, Prog and bHCG exposure.
Conclusion:  These findings suggest that E2, Prog and bHCG interfere with selected aspects of DC maturation and may thereby help preventing activation of allogenic T-cells by the embryo.