| In the external environment where human beings live,there are a large number of microorganisms-viruses,bacteria,fungi,protozoa and parasites.When these microorganisms invade the human body,these exogenous biological stimuli will induce the activation of immune system.The immune system can identify the key to alien invasion is due to its ability to identify the specific signs of these microorganisms-antigen.However,organ transplantation,as one of the main methods of treating end-stage endometriosis,will also bring exogenous antigens of the graft into the body.The immune system of the recipient will induce specific immune response by recognizing these foreign antigens,and this is transplant rejection.With the in-depth research,two types of transplant rejection were revealed,namely,cell rejection and humoral rejection.The cellular rejection is stimulated by allogeneic antigens,activated by T lymphocytes,cytokine production of interleukin(IL-2)and a large number of clonal proliferation of sensitized T lymphocytes.When the allogeneic organ implanted receptor,due to the donor and recipient of the different histocompatibility of the antigen,the T lymphocytes in the peripheral circulation of the recipient sensitized by the identification of the antigen on the graft,and then into the nearby peripheral immune organs,which is transformed into lymphoblast cells and rapidly proliferates into sensitized T lymphocytes.The sensitized CD8 + T cells(cytotoxic T lymphocytes)can directly attack the grafts while sensitized CD4 + cells(Th1 Type)can either release a number of cytokines such as IL-2,IL-6,interferon gamma(IFN-?),direct(cytotoxic subgroups)or indirectly(helper CD8 + T cells,natural killer cells and B lymphocytes)injured the graft.The humoral rejection is mediated by B lymphocytes,and B cells specific recognized graft antigen by BCR(B cell receptor,BCR),which is the activation of the first signal.The activation the second signal(co-stimulatory signal)of B cells is provided by the Th cells that interact with the B cell surface on the interaction of CD40 with CD154 and multiple adhesion molecule pairs.Activated B cells then enter the germinal center,through the differentiation process to form plasma cells or memory B cells,and plasma cells produce a large number of high affinity antibodies to effect on the graft.The classical theory of modern immunology suggests that antibody immune responses against TD antigens require the aid of CD4 + T cells.CD4 + T cells play an important role in B cell activation and humoral immunity.Traditional studies suggest that Th2 cells interact with B cells through CD40 / CD40 L,CD28 / B7 and secrete IL-4,IL-2 and so on to play a role in supporting B cell activation.However,after the activation,B cells in the peripheral immune organ must undergo somatic mutations,affinity maturation,receptor editing and type conversion process in germination cente,but whether these processes need T-cell support and how to assist or control the mechanism has not yet studied thoroughly.Through the study recent years,the Tfh cell subpopulation has been validated as a function of true B cell differentiation in the germinal center,and Tfh's own differentiation process has some understanding,but the underlying mechanism of the assisting has not been fully understood.The present study shows that IL-21 knockout mice develop Tfh cell differentiation disorder and affect further GC formation and antibody production.Therefore,IL-21 is one of the essential factors in Tfh cell differentiation process.In view of this feature in the Tfh differentiation process,we hope to protect the effect of the graft by blocking the IL-21 pathway by inhibiting the humoral rejection by targeting Tfh.1.Tfh cells regulate B cell differentiation and the mechanismIn the first part,we first extracted the mouse spleen naive T cells and stimulated it with IL-21.IL-21 could significantly activate the STAT3 pathway in T cells by protein blotting,which proved that IL-21 activated STAT3 to provide the signals for T cells differentiating to Tfh cells.Further study we hope that IL-21R-Fc could block the stimulation of IL-21 on T cells,so we first with IL-21R-Fc T cells pretreatment,and then further use IL-21 to stimulate it,the results Indicating that activation of STAT3 in T cells can be completely blocked by IL-21 at an IL-21R-Fc concentration of 10 ng / ml.Further studies investigated the effect of IL-21R-Fc blocking on IL-21 signaling pathway on the differentiation of Tfh cells by a mice humoral immunization(SRBC)model.Seven days after immunization with SRBCs,the mice treated with different treatments were detected.The ratio of mature B cells in peripheral blood was first examined,and there was no significant difference,which suggested that IL-21-Fc did not affect the differentiation of B cells in the bone marrow.However,IL-21R-Fc significantly inhibited the differentiation of Tfh cells after SRBC immunization.By analyzing the sporadic germinal center,Tfh cell differentiation was inhibited with the germinal center.The results showed that the number of follicular B cells was significantly reduced in IL-21R-Fc treatment,and it was proved that the response after SRBC immunization was specific humoral immune response.The plasma cells and the production of antibody were decreased by IL-21R-Fc treatment,revealing that IL-21R-Fc could inhibite the humoral rejection.2.Tfh cells regulate humoral rejection and its mechanismIn the first part of the experiment,we proved that IL-21R-Fc inhibited the differentiation of Tfh cells.Therefore,the second part of the experiment we used IL-21R-Fc treatment of recipient mice and cardiac ectopic transplantation.In the acute rejection of mouse heart transplantation,we increased the levels of IgG and C4 d in the grafts by increasing the number of serum plasma cells and the titer of the antibody,and proved that the acute rejection after transplantation Immune participation.The survival of the mice was prolonged by further experiments with IL-21R-Fc.The myocardium of the grafts was relatively good,the edema and necrosis of the myocardium were reduced,the infiltration of inflammatory cells was significantly reduced,the degree of swelling of the vascular endothelial cells was mild,TUNEL results IL-21R-Fc treatment also decreased the apoptosis of cardiomyocytes,and the detection of gold standard C4 d through the diagnosis of body fluid rejection also clearly indicated that IL-21R-Fc The infiltration of C4 d in the treated graft was significantly decreased.The plasma plasma cell count and antibody titer were also decreased by detecting the peripheral blood of the recipient.All the results demonstrate that IL-21R-Fc has an inhibitory effect on humoral rejection after cardiac transplantation in mice.Furthermore,we analyzed the spleen of the recipient's spleen and found that the number of Tfh cells in the spleen after IL-21R-Fc treatment was significantly decreased and the formation of the germinal center was also inhibited.This is consistent with the results of the first part,proving that IL-21R-Fc can also transplant Tfh cells in vivo.In conclusion,we first demonstrated that IL-21R-Fc could block the effect of IL-21 to activating the STAT3 pathway.By using the mouse humoral immune model,we demonstrated that IL-21R-Fc can inhibit the formation of germinal centers by inhibiting the differentiation of Tfh through the blocking of IL-21 pathway,and the process of B cell differentiation to plasma cells and memory B cells is inhibited,resulting in a decrease of antibody production.Further studies we used the acute rejection model of ectopic cardiac allograft in mice to prove that humoral immunity was involved,and IL-21R-Fc could inhibit this antibody-mediated rejection by Tfh inhibition,and it provides a new way of thinking to clinical humoral rejection treatment. |
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