A Study On The Role Of Soluble HLA-G Dimer In A "Human-Mouse"Xenogeneic Graft-versus-Host Disease Model

HLA-G is a non-classical HLA class I molecule which can induce a wide range of tolerogenic immunological effects via interaction with its inhibitory receptors. Current immune suppressive drugs aimed at maintaining tolerance to allografts have a major drawback of rendering the patient susceptible to infections. Inducing tolerance to allografts is currently the main task to be solved. Studies in vitro have shown that HLA-G induces immune tolerance in T, B, NK, DC, macrophages and other immune cells via interaction with their inhibitory receptors such as ILT-2/4. Clinical transplantation studies also have shown that HLA-G-positive recipients have short acute rejection and low chronic rejection incidence compared with HLA-G-negative recipients. Soluble HLA-G dimer can induce suppression of alloresponsive T cells in vitro, but the research in vivo is relatively less. Using a "Human-Mouse" X-GVHD model, we employed MLC to study the role of rapamycin and HLA-G dimer.1. Soluble HLA-G dimers can induce T cell toleranceTo study the role of soluble HLA-G dimers in inhibition of alloreactive T cells, we loaded the Tyr368-376peptide to the T2cell surface and co-cultured with HLA-A2negative lymphocytes, followed by addition of soluble HLA-G dimers to assess its intervention in this process. We collected the cells for detection and analysis by flow cytometry techniques after7days. The results showed that the soluble HLA-G dimers can inhibit T cell activation, inhibit alloreactive CD8+cell secretion of IFN-y, promote alloreactive CD8+cell secretion of IL-4, but had no effect on the alloreactive CD8+ cell secretion of TGF-beta.2. Soluble HLA-G dimer can not improve GVHR symptoms and prolong survival time of model miceIn order to further enrich the data in vivo, we established "Human-Mouse" X-GVHD model to explore the role of HLA-G dimer in vivo.The results showed that soluble HLA-G dimer can not improve the GVHR symptoms and prolong the survival time of model mouse. Then we found that the CD56+cells had an obvious proliferation in the xenogeneic mixed culture and this proliferation was enhanced with soluble HLA-G dimers. But proliferation of CD3+and CD14+cells was not apparent. Using only CD56+cells can not cause the occurrence of xenogeneic GVHR. The model mice survival time had been significantly extended using CD56+cell depleted PBMC. From the above experimental results we can conclude that the CD56+cells play a key role in the xenogeneic mixed culture, and they are the blasting fuse in xenogeneic GVHR.3. Rapamycin can prolong survival time of model mice with increasing MDSCsmTOR is an atypical serine/threonine protein kinase, that belongs to the phosphoinositide3-kinase (PI3K)-related kinase family. It’s a key kinase in cell growth and development and also the target of rapamycin. Rapamycin is a macrolide produced by the Streptomyces Hygroscopicus bacteria and that first gained attention because of its broad antiproliferat ive properties. We used the "human-mouse xenogeneic GVHD model combined with GM-CSF to explore the effect of rapamycin from in vivo and in vitro respectively. The results showed that rapamycin can prolong survival time of model mice with increasing MDSCs in vivo and induced proliferation of the MDSCs among PBMC in vitro.