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 rangeof tolerogenic immunological effects via interaction with its inhibitory receptors.Current immune suppressive drugs aimed at maintaining tolerance to allografts have amajor drawback of rendering the patient susceptible to infections. Inducing toleranceto allografts is currently the main task to be solved. Studies in vitro have shown thatHLA-G induces immune tolerance in T, B, NK, DC, macrophages and other immunecells via interaction with their inhibitory receptors such as ILT-2/4. Clinicaltransplantation studies also have shown that HLA-G-positive recipients have shortacute rejection and low chronic rejection incidence compared with HLA-G-negativerecipients. Soluble HLA-G dimer can induce suppression of alloresponsive T cells invitro, but the research in vivo is relatively less. Using a “Human-Mouse” X-GVHDmodel, 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 itsintervention in this process. We collected the cells for detection and analysis by flowcytometry techniques after7days. The results showed that the soluble HLA-G dimerscan inhibit T cell activation, inhibit alloreactive CD8+cell secretion of IFN-γ, promotealloreactive 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 survivaltime 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 thatsoluble HLA-G dimer can not improve the GVHR symptoms and prolong the survivaltime of model mouse. Then we found that the CD56+cells had an obviousproliferation in the xenogeneic mixed culture and this proliferation was enhanced withsoluble 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. Themodel mice survival time had been significantly extended using CD56+cell depletedPBMC. From the above experimental results we can conclude that the CD56+cellsplay a key role in the xenogeneic mixed culture, and they are the blasting fuse inxenogeneic GVHR.3. Rapamycin can prolong survival time of model mice with increasing MDSCsmTOR is an atypical serine/threonine protein kinase, that belongs to thephosphoinositide3-kinase (PI3K)-related kinase family. It’s a key kinase in cellgrowth and development and also the target of rapamycin. Rapamycin is a macrolideproduced by the Streptomyces Hygroscopicus bacteria and that first gained attentionbecause of its broad antiproliferat ive properties. We used the "human-mousexenogeneic GVHD model combined with GM-CSF to explore the effect of rapamycinfrom in vivo and in vitro respectively. The results showed that rapamycin can prolongsurvival time of model mice with increasing MDSCs in vivo and induced proliferationof the MDSCs among PBMC in vitro.