Lack of Histocompatibility Leukocyte Antigen-G expression in early embryos is not related to germinal defects or impairment of interleukin-10 production by embryos

The expression of Histocompatibility Leukocyte Antigen (HI-A)-G molecules is a mandatory prerequisite for the development of pregnancy but no hypotheses have yet been advanced regarding the lack of HLA-G modulation expression in a percentage of early embryos obtained by in vitro fertilization (IVF). One possible hypothetical model assumes that the absence of regulation of HLA-G or impaired interleukin (IL)-10 secretion could be related to germinal defects. We investigated the presence of soluble HLA-G antigens in supernatants of single embryo cultures from couples admitted to a second fertilization procedure; these couples showed a complete absence of HLA-G modulation in the first cycle's embryo supernatants (0/31). The results obtained in the second IVF cycle showed embryo supernatants positive for HLA-G (14/40), suggesting that the previous lack of antigen modulation is independent of germinal defects. Furthermore, since it has been reported that oocytes and early embryos can secrete IL-10, an anti-inflammatory cytokine produced by type 2 helper T cells that induces upregulation of HLA-G expression in monocytes and trophoblasts, we investigated the levels of IL-10 and soluble HLA-G in 40 embryo culture supernatants from 21 IVF cycles. No associations were observed between the presence of IL-10 and the production and concentrations of soluble HLA-G, or between IL-10 levels and pregnancy outcome. These results indicate that the lack of HLA-G production in early embryos is not related to germinal defects or to impairment in embryo IL-10 secretion but could be ascribed to possible uncorrected fertilization processes.