Human leukocyte antigen-G (HLA-G) is a non-classical class I HLA molecule that is expressed by extravillous cytotrophoblast cells. This protein may play a critical role in the protection of cytotrophoblasts from maternal immune response, allowing these semi-allogeneic cells to invade the uterus unimpeded. We have demonstrated that diminished placental HLA-G expression is associated with pre-eclampsia. In order to explore fundamental mechanisms underlying this reduced HLA-G expression in pre-eclampsia, we looked for, and found by sequences analysis, a single base-pair mutation in the HLA-G gene 3'-untranslated region (3'UTR) adjacent to an AUUUA motif. This mutation is significantly associated with pre-eclampsia, the severe form being more strongly associated with homozygosity for this mutation than the mild form. Since the null allele was discovered in the HLA-G mRNA 3'UTR adjacent to an AUUUA motif, we also examined the effect of this mutation on HLA-G mRNA stability, and found that half-lives of HLA-G mRNA with the mutation were significantly shorter than without the mutation. These data provide evidence that this mutation could be one of the fundamental mechanisms for lower levels of placental HLA-G protein expression in patients with pre-eclampsia.

No abstract

SUMMARYHuman leucocyte antigen (HLA) -G is expressed on trophoblast cells during pregnancy, suggesting a role in protection of the semiallogeneic fetus. Published data suggest that HLA-G protects a cell against natural killer cell lysis. It has been hypothesized that HLA-G may also protect the fetus by preventing allo-cytotoxic T lymphocyte (CTL) responses. To test this hypothesis, we assayed the effects of various concentrations of puri®ed HLA-G on CTL response in a mixed lymphocyte culture (MLC) system. We found that concentrations i 0 . 1 mg/ml of HLA-G suppressed the allo-CTL response by 30±100% over the control, but, paradoxically, concentrations of 0 . 01±0 . 05 mg/ml of HLA-G augmented the allo-CTL response by 25±50% over the control. Concentrations j 0 . 001 mg/ml HLA-G had no effect. Addition of HLA-G to preprimed allo-CTL effector cells did not affect their killing ability. Allo-CTL suppressive doses of HLA-G induced a T helper type 2 (Th2) cytokine response, whereas allo-CTL-enhancing doses of HLA-G induced a Th1-type cytokine response. HLA-G puri®ed from ®rst-trimester placenta does not affect allo-proliferative responses nor does it alter the percentage of CD4 + or CD8 + T cells in MLCs. These ®ndings support a potential role for HLA-G-mediated suppression of allo-CTL formation in normal pregnancies. In addition, the effects observed at lower concentrations of HLA-G may have interesting implications for the condition of pre-eclampsia in which concentrations of this HLA class I molecule are reduced.

No abstract

No abstract

Our findings suggest that HLA-G may have potential clinical implications in diagnosis, prognosis, and immunotherapy of patients with breast cancer.

Overall, our results indicated that the expression of HLA-G is a characteristic feature of gastric carcinoma and that immunostaining by anti-HLA-G antibody may be a potentially useful prognostic indicator.

The effect of progesterone on HLA-G gene expression is through progesterone receptor (PR) activation, followed by binding to a novel PRE in the HLA-G promoter region. Therefore, one of the mechanisms of immunomodulation by progesterone during pregnancy may be through the regulation of HLA-G gene expression via this novel PRE.