Old game, new players: Linking classical theories to new trends in transplant immunology

The evolutionary emergence of an efficient immune system has a fundamental role in our survival against pathogenic attacks. Nevertheless, this same protective mechanism may also establish a negative consequence in the setting of disorders such as autoimmunity and transplant rejection. In light of the latter, although research has long uncovered main concepts of allogeneic recognition, immune rejection is still the main obstacle to long-term graft survival. Therefore, in order to define effective therapies that prolong graft viability, it is essential that we understand the underlying mediators and mechanisms that participate in transplant rejection. This multifaceted process is characterized by diverse cellular and humoral participants with innate and adaptive functions that can determine the type of rejection or promote graft acceptance. Although a number of mediators of graft recognition have been described in traditional immunology, recent studies indicate that defining rigid roles for certain immune cells and factors may be more complicated than originally conceived. Current research has also targeted specific cells and drugs that regulate immune activation and induce tolerance. This review will give a broad view of the most recent understanding of the allogeneic inflammatory/tolerogenic response and current insights into cellular and drug therapies that modulate immune activation that may prove to be useful in the induction of tolerance in the clinical setting.

Inhibitory effect of cyclosporin A on the immunological rejection of rats with cerebral hemorrhage following transplantation of nerve growth factors transfected glial cells

BACKGROUND： At present, it has been confirmed that immunological rejection exists in the cell transplantation in brain tissue, the effects of immunosuppressant on the immunological rejection and the survival of grafts in brain cell transplantation are worthy being investigated further. OBJECTIVE： To observe the immunological rejection after transgeneic cell transplantation in treating cerebra hemorrhage in rats, and investigate the interventional effect of cyclosprin. DESIGN ： A randomized controlled study SETTINGS： Second Affiliated Hospital of Xuzhou Medical College; First Affiliated Hospital of Nanjing Medica University. MATERIALS： Thirty-five healthy clean-degree SD rats of 6-8 weeks old were used, weighing 200-250 g, either male or female; The FACSort flow cytometer （American BD Company） and NYD-1000 image analytical system were used, The rat-anti-rat CD4 monoclonal antibody, rat-anti-rat CD8 monoclonal antibody, and rat-anti-rat MHC Ⅱ antigen monoclonal antibody were purchased from Santa Cruz Company; SP and DAB kits were purchased from Beijing Zhongshan Bio-engineering Company. XSP-8C2 light microscope was the product of Shanghai Zousun Optical Instrument, Co.,Ltd, and KYKY-3800B electron microscope was the product of China KYKY Technology Development Co.,Ltd. METHODS ： The experiments were carried out in the animal experimental center of Nanjing Medical University from April to July in 2003. ① Model establishment： The rats were anesthetized, and then the coordinates of left internal capsule were identified, and the needle was withdrawn after 120 μL blood was injected into the internal capsule. Adenoviruses were taken as the carriers, after the astrocytes were successfully transfected by nerve growth factor（NGF） gene, 0.2 mL cell suspension was injected into the sites of cerebral hemorrhage. Thirty successfully established rat models were randomly divided into cyclosporin A group （n=18） and control group, the rats were treated with intraperitoneal injection of cyclosporin A （10 mg/kg per day） intraperitoneal injection of saline of the same dosage from the 1^st day after transplantation, once a day for 7 days continuously.② CD4^＋ and CD4^＋ detection： The CD4^＋ and CD4^＋ T lymphocytes in caudal vein were counted with flow cytometer at 15 days after treatment. ③ Morphological observation in the transplanted sites： The rats were killed and then brain tissues were taken out, the transplanted sites and the structure of the normal brain tissue around the transplanted sites were observed with light and electron microscopes. ④Detections of the infiltration of T lymphocyte subsets and expression of major histocompatibility complex （MHC） Ⅱ antigen in the transplanted sites： The image analysis of immunohistochemical sections was performed with the image analytical system, and the integral optical density （IOD） was taken as the statistical value to observe the infiltration of T lymphocyte subsets and expression of MHC Ⅱ antigen in the transplanted sites, and the normal brain tissue around the transplanted sites were taken as controls. MATN OUTCOME MEASURES： ① Countings of CD4^＋ and CD4^＋ in peripheral blood; ②Results of the morphological observation in the transplanted sites; ③ Infiltration of T lymphocyte subsets and expression of MHC Ⅱ antigen in the transplanted sites RESULTS ： Totally 35 rats were used, and 30 were successfully made into models, 5 died during the treatment, the other 25 were involved in the analysis of results. ① Results of CD4^＋ and CD4^＋ T lymphocytes in pedpherel blood： The percentages of CD4^＋ and CD4^＋ T lymphocytes in the cyclosporin A group were （29.20±3.97）% and （20.65±2,02）%, respectively, which were obviously lower than those in the control group [（47,39±3,01）%, （28.30±2.36）%, t=-4.983, 4.012, P 〈 0.05], and the CDC/CD4^＋ ratio was obviously lower than that in the control group （1,41±0.86, 1,64^＋0.69, t=-3. 871, P〈 0.05）.② Morphological results in the transplanted sites： Under optical and electron microscopes, the survival region of the transplant was round, and it had an unobvious migration region with the normal brain tissues, the grafts had normal cellular form. Infiltrations of lymphocytes and monocytes were observed in both groups, and mainly located in the transplanted sites, and the expression of lymphocytes in the cyclosporin A group was markedly lower than that in the control group, and no above-mentioned changes were observed in the normal brain tissue around the transplanted sites. ③ Results of CD. and CD4^＋ T lymphocytes and expression of MHC Ⅱ antigen in the transplanted sites： The CD4^＋ and CD4^＋ T lymphocytes and expression of MHC Ⅱ antigen in the transplanted sites were observed in both groups. The IOD of CD4^＋ and CD4^＋ antigen positive cells in the cyclosporin A group were obviously lower than those in the control group （1.85±0.38, 1.44^＋0.33; 3.33±0.37, 2.648±0.56, /=-4.122, 4.434, P〈 0.05）, and the IOD of MHC Ⅱantigen positive cells was markedly lower than that in the control group （0.76±0.22, 0.94±0.24, t=3.885, P 〈 0.05）. CONCLUSION： There is immunological rejection in brain tissue after the transplantation of NSC transgeneic glial cells. ② The immunosuppressant of cyclosporin A can reduce the immunological rejection after the cell transplantation.

THE MUTUAL BENEFIT ROLE OF LIVER AND PANCREAS IN COMBINED TRANSPLANTATION

The present study observed the mutual benefit role of liver and pancreas in combined hepaticopan-creatic transplantation in rats. The results indicated that pancreas, when transplanted with liver, could survive for a significant long time (13. 4±1.01 days) than it transplanted alone (9. 2±1.14 days) (P< 0. 05, t test). The interstitial rejection was mild and its rejection grade was significantly different from that of pancreas transplanted alone (P<0. 05, X2 test). The liver, when transplanted with pancreas, regenerated with strong competence and contact structure morphologically compared with liver transplanted alone. We think that pancreas could be immunologically protected against rejection and liver can be nutri-tionalized by pancreas in combined liver and pancreas transplantation.

Increase of peripheral Th17 lymphocytes during acute cellular rejection in liver transplant recipients

BACKGROUND: Although many human inflammatory and autoimmune diseases were previously considered to be mediated by T helper type 1 (Th1) cells, the recently described Th17 cells play dominant roles in several of these diseases. We and others speculated that allograft rejection after organ transplantation may also involve Th17 cells. Episodes of acute rejection occur in 30% of liver transplants. This study aimed to determine the frequency of circulating Th17 cells in patients who had received liver transplants for benign end-stage liver disease and to identify any association between acute rejection episodes and levels of Th17 cells in the peripheral blood. METHODS: A prospective study compared Th17 cells from 76 consecutive benign end-stage liver disease patients who had undergone orthotopic liver transplantation from 2007 to 2011 with those from 20 age-matched healthy individuals. Peripheral blood samples were collected at different time points within one year after transplant. Blood samples and liver biopsies were also collected at the diagnosis of acute rejection. Percentages of circulating CD4+ IL-17+ cells were measured by flow cytometry The transplant patients were classified into two groups: a rejection group consisting of 17 patients who had an episode of acute rejection, and a non-rejection group comprising the remaining 59 patients with no acute rejection episodes Percentages of circulating Th17 cells were compared between the two groups and controls. RESULTS: The levels of circulating CD4+ IL-17+ T cells in the rejection group were higher during acute rejection than those in the non-rejection group (2.56±0.43% versus 1.79±0.44% P<0.001). The frequency of CD4+ IL-17+ cells in peripheral blood was positively correlated with the rejection activity index (r=0.79, P=0.0002).CONCLUSION: Circulating Th17 cells may be useful as a surrogate marker for predicting acute rejection in liver transplant recipients.

CD28/B7-MEDIATED COSTIMULATION IS REQUIRED FOR PARATHYROID GLAND ALLOGRAFT REJECTION IN RATS

The activation of T cells to differentiate and to proliferate is an essential step in the immune response to antigen, especially in cell mediated acute allograft rejection. Besides the interaction of CD3/TCR complex with Ag/MHC complex presented on antigen presenting cells, a complete T cell activation and proliferation requires a second costimulatory signal. The interaction of CD28/CTLA 4 and B7 is a major costimulatory pathway for T Cell activation. Inhibition of this pathway results in development of antigen specific unresponsiveness and clonal anergy.In present study,the biologic function of anti CD28 monoclonal antibody and its Fab fragment were investigated in vitro and in vivo.The results indicate that mAbCD28 and its Fab fragments could promote the functional recovery of allografts and prolong the graft survival,but could not reverse the acute rejection or induce transplantation tolerance in the rat PTG allograft model. We also found that peripheral TNF α level and NK cell activity were suppressed in the presence of mAbCD28 and its Fab fragments for a relatively long time after PTG transplantation.

Suppressive effects of antigens on the activity of specific activated lymphocytes : A test to define the specificity of activated lymphocytes

Objective：With the regular mixed lymphocytes culture （MLC） to detect the allograft rejection, the reactivity of the activated lymphocytes （primed lymphocytes） of a recipient shows sometimes increase and sometimes decrease against the antigens from the donor, which is inconsistent with the clinical results. In order to establish a convenient method for testing the specificity of the activated lymphocytes in vitro, so as to know the rejection occurred or not by testing the existence of the specific activated lymphocytes against donor＇s HLA antigens in the recipient＇s peripheral blood. Methods： Anti-IL-2 neutralizing monoclonal antibody （anti-IL-2 N-mAb） and immunosuppressors were introduced in this test system in the presence of specific stimulators and activated lymphocytes. Results ： When the activated lymphocytes were chosen from the one-way MLC 4 d to undergo re-stimulation by specific stimulators, the activity of activated lymphocytes in the treatment group was suppressed significantly compared with that in the control group. The result of this test method is consistent with the biopsy in the clinical diagnosis of rejection. Conclusion：h suggests that the activated lymphocytes can be inactivated by specific antigens in certain conditions. This can be a useful tool to define the specificity of the activated lymphocytes.

A naturally occurring CD8^＋CD122^＋ T-cell subset as a memory-like Treg family

Despite extensive studies on CD4^＋CD25^＋ regulatory T cells （Tregs） during the past decade, the progress on their clinical translation remains stagnant. Mounting evidence suggests that naturally occurring CD8^＋CD122^＋ T cells are also Tregs with the capacity to inhibit T-cell responses and suppress autoimmunity as well as alloimmunity. In fact, they are memory-like Tregs that resemble a central memory T cell （TcM） phenotype. The mechanisms underlying their suppression are still not well understood, although they may include IL-IO production. We have recently demonstrated that programmed death-1 （PD-1） expression distinguishes between regulatory and memory CD8^＋CD122^＋ T cells and that CD8^＋CD122^＋ Tregs undergo faster homeostatic proliferation and are more potent in the suppression of allograft rejection than conventional CD4^＋CD25^＋ Tregs. These findings may open a new line of investigation for accelerating effective Treg therapies in the clinic. In this review, we summarize the significant progress in this promising field of CD8^＋CD122^＋ Treg research and discuss their phenotypes, suppressive roles in autoimmunity and alloimmunity, functional requirements, mechanisms of action and potential applications in the clinic.