Inhibition of the activating signals in NK92 cells by recombinant GST-sHLA-G1α chain

The soluble HLA-G1 (sHLA-G 1) isoform was found to be secreted by trophoblast cells at the materno-fetal interface, which suggests that it may act as an immunomodulator during pregnancy. In this paper, we reported that GST-sHLA-G1alpha chain could bind to its receptor ILT-2 on NK92 cells and then the latter recruited Src homology 2 domain-containing tyrosine phosphatase-1 (SHP-1), which consequently dephosphorylated some important protein tyrosine kinases and blocked the activation of downstream molecules such as MEK and ERK so that the cytotoxicity of natural killer (NK) cells was inhibited. These results indicated that GST-sHLA-G1alpha chain might be exploited in new immunotherapy strategies aiming at inducing immunotolerance during allograft, xenograft and autoimmune situations. In addition, we found that modification of O-linked beta-N-acetylglucosamine (O-GlcNAc) was involved in NK cells' activating and inhibitory signals. This may provide a novel molecular target for inducing immunotolerance but needs further study.