Effects Of Halofuginone On Maturation Of Dendritic Cells And Immune Tolerance During Homograft Heart Transplantation Of Rats

Objective So far there is still no better way to prevent and treat the inevitable emergence of immune tolerance after heart transplantation. Immune responses occur in several steps, APC (antigen presenting cells, APCs) uptake of antigens at first followed by interaction with T cells:on the one hand, APC processed and presented antigen to CD4+T helper lymphocytes (T helper cell,Th cells), induce cell immune response, and activate B cell immune response;on the other hand, if Th cell is not activated,immune tolerance occurs. Recent study about immune tolerance reveals immunoregulatory cells,especially APC and Treg cells (regulatory T cells),play an important role in the clinical transplant immune tolerance. Thus, the activation of the immune response or immune tolerance induction and ability for effective antigen presentation has a direct relationship.Dendritic cells are highly efficient APC which have the ability to regulate both innate and adaptive immune response.DC are considered to play crucial roles in initiation and regulation of the body’s immune response. It can uptake, processing, and handling antigen, and the antigen was subsequently presented to T lymphocytes. However, unlike the other antigen presenting cells, the greatest feature of DC is the ability to significantly stimulate the proliferation of naive T cells (naive T cells).So DC is the initiation of the body’s adaptive T cell immune response and has a unique position in the induction of adaptive T cellular immune response.DCs were first discovered in1973as a novel cell population in mouse spleen that was clearly distinct from macrophages. Under normal circumstances, the vast majority of DC in vivo is in the immature state(imDC), imDC expressing low levels of co-stimulatory molecules, adhesion molecules,and having a weak ability to stimulate the MLR in vitro,but with a strong capacity of endocytosis and the antigen-processing.When DC uptake antigens, or stimulated by certain factors (mainly inflammatory signals, such as IL-1β, TNF-a, LPS), it would migrate to lymphoid organs, gradually differentiate into mature DC(mDC), and the capacity of MHC class I molecules, costimulatory molecules, adhesion molecules expression would significantly increased, and would have a strong ability to stimulate the MLR in vitro while the capacity of antigen uptake and processing declined. DC maturation state and their functions are closely related, therefore, it has great significance to study the mechanism of DC phenotypic and functional maturation.Current use of donor immature dendritic cells to immune tolerance induced receptor has been initially successful with further understanding of the function of dendritic cells in the immune response process,but several problems still remaining, such as under the external stimulation of a variety factors、imDC easily get matured and mediate immune tolerance.Then the inhibition maturation of DC might be a new way to suppress the immune tolerance.At present, the technology of cell culture of bone marrow-derived dendritic cells in vitro and the establish of heart transplantation model of rats has become mature, which has laid the foundation of the subject.We recently demonstrated that halofuginone(HF),a widely studied derivative of febrifugine,inhibits mouse and human Thl7differentiation by activating a cytoprotective signaling pathway,and could also inhibits the development of Thl7-driven autoimmunity in a mouse model of multiple sclerosis by activating the amino acid response pathway. Leiba M.et al., have found that halofuginone inhibit NF-kappaB and p38MAPK pathway of efficient T cells.And these two pathways have been confirmed is closely related to the activation of the immune response,which certifies the halofuginone has a certain degree of effection for the generation of immune response.Nowadays,due to the lack of report on effects of halofuginone on regulation of dendritic cells,it is unkown to see if it passes to affect Th cell activation by regulate the activities of DC, or regulate immune tolerance by affect the maturation of imDC,or by other means to impact on the body’s immune response.In this study, to further understanding of the role of halofuginone in immune regulation,we take bone marrow derived dendritic cells of rats in vitro as an object to observe the effects of halofuginone on maturation of dendritic cells and immune tolerance during homograft heart transplantation of rats, in order to provide new ways and means to treat transplantation tolerance and to explore its possible mechanism.Methods We isolated rat bone marrow derived dendritic cells and investigated the effects of halofuginone in LPS-treated DCs by flow cytometry;we established heart transplantation model of rats, and observed the effect of halofuginone stimulated dendritic cells in the immune tolerance by pathological analysis and mixed lymphocyte reaction.Conclusion This study systematically observed for the first time in vivo and in vitro that halofuginone can inhibit the maturation of rat bone marrow-derived dendritic cells and lymphocyte proliferation.