Expression of Epstein-Barr Virus-Induced Gene 3, an Interleukin-12 p40-Related Molecule, throughout Human Pregnancy

Abstract

In human pregnancy, trophoblasts are the only cells of fetal origin in direct contact with the maternal immune system: syncytiotrophoblasts are in contact with maternal blood, whereas extravillous trophoblasts are in contact with numerous maternal uterine natural killer (NK) cells. Therefore, trophoblasts are thought to play a key role in maternal tolerance to the semiallogeneic fetus, in part through cytokine production and NK cell interaction. Epstein-Barr virus-induced gene 3 (EBI3) encodes a soluble hematopoietin receptor related to the p40 subunit of interleukin-12. Previous studies indicated that EBI3 is expressed in the spleen and tonsils, and at high levels in full-term placenta. To investigate further EBI3 expression throughout human pregnancy, we generated monoclonal antibodies specific for EBI3 and developed an EBI3 enzyme-linked immunosorbent assay. Immunohistochemical experiments with EBI3 monoclonal antibody on first-, second-, and third-trimester placental tissues demonstrated that EBI3 was expressed throughout pregnancy by syncytiotrophoblasts and extravillous trophoblasts (cytotrophoblast cell columns, interstitial trophoblasts, multinucleated giant cells, and trophoblasts of the chorion laeve). EBI3 expression was also induced during in vitro differentiation of trophoblast cell lines. In addition, large amounts of secreted EBI3 were detected in explant cultures from first-trimester and term placentae. Consistent with these data, EBI3 levels were strongly up-regulated in sera from pregnant women and gradually increased with gestational age. These data, together with the finding that EBI3 peptide is presented by HLA-G, suggest that EBI3 is an important immunomodulator in the fetal-maternal relationship, possibly involved in NK cell regulation.

Timing of IFN-β Exposure during Human Dendritic Cell Maturation and Naive Th Cell Stimulation Has Contrasting Effects on Th1 Subset Generation: A Role for IFN-β-Mediated Regulation of IL-12 Family Cytokines and IL-18 in Naive Th Cell Differentiation

“…To date, neither free EBI3 nor p35/EBI3 has known functional activity. In addition, p35/EBI3 heterodimer has only been reported intracellular in primary cells (i.e., not secreted) (46), and consistent with this observation, we did not detect p35/EBI3 in DC supernatants (data not shown). Together these findings indicate that the effects of anti-EBI3 mAb in blocking Th cell IFN-␥ and TNF-␣ secretion (Fig.…”

“…4) recognizes not only IL-27, but also free EBI3 and p35/EBI3 heterodimer (46). To date, neither free EBI3 nor p35/EBI3 has known functional activity.…”

“…The following mAbs were used for the blocking experiments: anti-IL-12 p40 mAb clone B-P24 (IgG1) and anti-IL-12 p35 clone B-T21 (IgG1; Cell Sciences, Norwood, MA), anti-IL-18 (IgG1; MBL, Watertown, MA), MOPC21 (IgG1; ICN, Costa Mesa, CA), and anti-EBI3 mAbs 1A1 (IgG1) as previously described (27).…”

“…An EBI3 ELISA, developed by us (27), was used to determine levels of combined free EBI3 plus IL-27 p28/EBI3. An IL-27 ELISA, recognizing only IL-27 p28/EBI3, was made available by Dr. R. Kastelein (DNAX, Palo Alto, CA) (12).…”

Human CD4+CD25+Foxp3+ Regulatory T Cells Do Not Constitutively Express IL-35

“…Peroxidase reaction was developed with chemiluminescence reagents (Pierce). EBI3 ELISA was performed as previously described (10). It detects both free EBI3 and EBI3 complexed with either p28 or p35 (detection limit, 1 ng/ml).…”