Recognition of nonclassical HLA class I antigens by gamma delta T cells during pregnancy.

The healthy trophoblast does not express classical HLA-A and HLA-B products; therefore, an MHC-restricted recognition of trophoblast-presented Ags is unlikely. In the decidua and also in peripheral blood of healthy pregnant women, gammadelta T cells significantly increase in number. We investigated the possible role of gammadelta T cells in recognition of trophoblast-presented Ags. PBL and isolated gammadelta T cells from healthy pregnant women as well as from those at risk for premature pregnancy termination were conjugated to choriocarcinoma cells (JAR) transfected with nonclassical HLA Ags (HLA-E, HLA-G). To investigate the involvement of killer-inhibitory/killer-activatory receptors in trophoblast recognition, we tested the effect of CD94 block on cytotoxic activity of Vdelta2(+) enriched gammadelta T cells to HLA-E- and/or HLA-G-transfected targets. Lymphocytes from healthy pregnant women preferentially recognized HLA(-) choriocarcinoma cells, whereas those from pathologically pregnant patients did not discriminate between HLA(+) and HLA(-) cells. Normal pregnancy Vdelta2(+) T cells conjugated at a significantly increased rate to HLA-E transfectants, whereas Vdelta2(+) lymphocytes from pathologically pregnant women did not show a difference between those and HLA(-) cells. Blocking of the CD94 molecule of Vdelta2(+) lymphocytes from healthy pregnant women resulted in an increased cytotoxic activity to HLA-E-transfected target cells. These data indicate that Vdelta2(+) lymphocytes of healthy pregnant women recognize HLA-E on the trophoblast, whereas Vdelta1 cells react with other than HLA Ags. In contrast to Vdelta2(+) lymphocytes from healthy pregnant women, those from women with pathological pregnancies do not recognize HLA-E via their killer-inhibitory receptors and this might account for their high cytotoxic activity.