Tolerance-inducing By Dendritic Cells Transduced Immunoglobulin-like Transcript In Vitro

Allogeneic Hematopoietic Stem Cell Transplantation (Allo-HSCT) is the only way to revolutionized hematopoietic malignancies. However, graft-versus-host disease (GVHD) is still a major complication of Allo-HSCT and playing a pivotal role in the curative effect. The quest for a revolution to GVHD has just begun. GVHD is mediated by donor T cell that can recognize minor histoconpatibility antigens (miHAs), which are peptides derived from intracellular proteins which distinguish host from donor. Following the presentation of miHAs by antigen presenting cells (APC), donor T cell are triggering by miHAS bound to MHC classⅠand classⅡantigen, respectively, to induce GVHD. Immunodepressant have a dominant role in preventing and curing graft rejections in both research and clinical practice, but it can cause side effects such as hepar and renal toxicity, severe opportunistic infection etc. Nowadays, hot and tough problems in transplantation field are how to induce immune tolerance of grafts. Removal of donor-derived T lymphocytes prior to transplantation efficiently ameliorates GVHD. However, short of T cells in graft can lower the graft-versus-leukemia (GVL) effect notably. The statistical results showed removal of donor-derived T lymphocytes prior to transplantation has been resulted in an increased incidence of recurrence of leukemia. Several clinical and experimental studies support the idea that GVHD and GVL are mediated not by the same (host-specific) T cell but also by distinct (leukemia-specific) alloreactive donor T-cell populations. GVHD has been associated with Th1 cell which aim at major and minor histocompatibility antigens, and GVL has associated with Th2 cell. Moreover, the ideal method is how to leave behind the GVL reaction without causing GVHD.Dendritic cells (DC) are the most potent professional antigen presenting cell, playing a pivotal role in the induction of both immunity and tolerance. In some condition, DCs can present antigen, express CM, excrete CK, activate T lymphocytes, and finally form immune systems. Under the other conditions, DCs can forms tolerance of grafts. Recent reports suggest that transgenation of DCs with immune suppression gene can increase their tolerogenic potential. Consequently, gene-modified DCs induce immune tolerance of grafts, and prolong survival time of grafts.Immunoglobulin-like transcript (ILT) 3 and 4, a suppressive receptor, which express in DC, play an important role in the form of DC tolerance. Researches indicated that Vitamin D3 and CK (IL-10, IFN-α) can induce immature DCs to DC tolerance. DCs stimulated with IL-10 could expressed high ILT-4 and low CM (CD80, CD86).It suggests high-expressed ILT-3, ILT-4 can mediate a immune tolerance.In this study we proposed that host bonemarrow-derived DC transduced to express ILT can delete alloreactive cells from donor haematopoietic stem cell grafts in vitro, and transplanting this manipulated grafts may prevent GVHD and keep GVL and antiviral immunity effects.Part one: To construct and identify the adenovirus vector combinated by ILT, transfer ILT virus into DCs in vitro, then detect bionomics of the DCs and observe the effects. Result: ILTmRNA could be detected by RT-PCR in DCs transferred with ILT, which indicated that adenovirus vector could effectively transfer DCs. Through DCs and ILT-DC analyzed by FACS, we observed that DCs transduced with ILT gene consistent with untransduced DCs surface phenotype.Part two: To investigate mechanisms of ILT-DC to induce immune tolerance by the regulation of regulatory T cells and apoptosis. Result: Mixed lymphocyte reactions (MLR) DCs, ILT-DCs with donor derived T cell showed that ILT-DC might inhibit activated T cell proliferation. We found that ILT-DC could induce T cells apoptosis analyzed by AnnexinV/PI.In conclusion, we have established an allogeneic model system that allows elimination of alloreactive T cells by ILT-DC. Transfer a modified allogeneic donor T lymphocyte repertoire into a BMT model demonstrated that depletion of alloreactive T cells was sufficient for preventing a lethal GVHD in recipients. Thus, ILT-DC for elimination of alloreactivity in allogeneic transplants might represent a suitable strategy for preventing a lethal GVHD.