Generation and functional assessment of nonhuman primate regulatory dendritic cells and their therapeutic efficacy in renal transplantation.

Nonhuman primates (NHP) are important pre-clinical models for evaluation of the safety and efficacy of the most promising potential therapeutic advances in organ transplantation based on rodent studies. Although rare, dendritic cells (DC) play important roles in preservation of self tolerance and DC with immunoregulatory properties (regulatory DC; DCreg) can promote transplant tolerance in rodents when adoptively transferred to allograft recipients. NHP DCreg can be generated ex vivo from bone marrow precursors or blood monocytes of cynomolgus or rhesus macaques or baboons. NHP DCreg generated in the presence of anti-inflammatory factors that confer stability and resistance to maturation, subvert alloreactive T cell responses. When infused into rhesus renal allograft recipients before transplant, they safely prolong MHC mis-matched graft survival, associated with attenuation of anti-donor immune reactivity. In this concise review we describe the properties of NHP DCreg and discuss their influence on T cell responses, alloimmunity and organ transplant survival.

Tolerance--is it worth it?

We are entering an exciting time in the study of immunologic tolerance. Several cellular and molecular strategies have been developed that show promise in nonhuman transplant models and these approaches are just now appearing in clinical trials. Tolerance strategies that prevent immune rejection and obviate the need for immunosuppressive medications (with inherent risk of cancer, infection, and organ toxicity) would improve both graft and patient survival. Each tolerance protocol brings its own set of associated risks. As the results of these trials become available, we must continue to evaluate their successes and failures. The balance of these outcomes will help us answer the question: "Tolerance-Is it worth it?"

Vascularized composite allografts and solid organ transplants: similarities and differences.

PURPOSE OF REVIEW: Vascularized composite allotransplantation (VCA) is a treatment for complex tissue injuries and defects of extremities and face. During the past thirteen years, more than 100 VCA cases have been reported. Form and function restored with VCA have exceeded the results achieved with conventional surgical techniques. The review summarized the development in VCA over the past 12 months with references of and comparison with solid organ transplantation. RECENT FINDINGS: The highlights reported in the latest publications included a better understanding of topical immunosuppressants for prevention and treatment of VCA rejection, mechanisms of chronic rejection and minimization of immunosuppressive maintenance treatment using a cell-based protocol in human upper-extremity transplantation. SUMMARY: We herein summarize the progress made in VCA in the last year with a focus on new clinical immunosuppressive strategies and novel targets for immunosuppression and immunomodulation including the application of mesenchymal stem cells for transplant tolerance.

Isolation, expansion and functional assessment of CD4+CD25+FoxP3+ regulatory T cells and Tr1 cells from uremic patients awaiting kidney transplantation.

BACKGROUND: The immunosuppressive properties of regulatory T cells have emerged as an attractive tool for the development of immunotherapies in various disease contexts, e.g. to treat transplantation induced immune reactions. This paper focuses on the process of obtaining and functionally characterizing CD4+CD25+FoxP3+ regulatory T cells and Tr1 cells from uremic patients awaiting kidney transplantation. METHODS: From October 2010 to March 2011 uremic patients awaiting living donor kidney transplantation, and their corresponding kidney donors, were enrolled in the study. A total of seven pairs were included. Isolation of CD4+CD25+FoxP3+ regulatory T cells was performed by magnetic activated cell sorting of peripheral blood mononuclear cells obtained from the uremic patients. Donor specific Tr1 cells were differentiated by repetitive stimulation of immature CD4+ T cells with immature dendritic cells, with the T cells coming from the future kidney recipients and the dendritic cells from the corresponding kidney donors. Cells were then expanded and functionally characterized by the one-way mixed leukocyte reaction and assessment of IL-10 production. Phenotypic analysis was performed by flow cytometry. RESULTS: The fraction of CD4+CD25+FoxP3+ regulatory T cells after expansion varied from 39.1 to 50.4% and the cells retained their ability to substantially suppress the mixed leukocyte reaction in all but one patient (3.8-19.2% of the baseline stimulated leukocyte activity, p<0.05). Tr1 cells were successfully differentiated from all but one patient and produced high levels of IL-10 when stimulated with immature dendritic cells (1,275-11,038% of the baseline IL-10 secretion, p<0.05). CONCLUSION: It is practically feasible to obtain and subsequently expand CD4+CD25+FoxP3+ regulatory T cells and Tr1 cells from uremic patients without loss of function as assessed by in vitro analyses. This forms a base for adoptive regulatory T cell therapy in the setting of living donor kidney transplantation.

Human regulatory macrophages as a cell-based medicinal product.

PURPOSE OF REVIEW: To consolidate our basic scientific and technological appreciation of human regulatory macrophages (M reg) as a cell-based medicinal product for use as an adjunct immunosuppressive therapy in organ transplantation. RECENT FINDINGS: Building on the original observation that crude preparations of IFN-γ-stimulated allogeneic macrophages prolong allograft survival in experimental animals, we have arrived at a detailed understanding of the derivation, phenotype and T-cell-suppressive potential of a population of in-vitro-derived human macrophages, which have been designated M regs. This basic scientific knowledge has inspired methodological advances in M reg manufacture, leading to a purer and more homogeneous cell product. In turn, cells produced by these improved protocols have been applied in the clinic, so completing a cycle of technological development. Studying the migration and physiological impact of M reg administration in patients provides a measure of reassurance that the procedure is well tolerated. Cutting-edge strategies to assess the immunological status of solid organ transplant recipients allow the biological effects of M reg treatment to be monitored. SUMMARY: A view of the human M reg as a novel, stringently defined medicinal product is presented, opening exciting possibilities for its future investigation as a therapy in solid organ transplantation and beyond.

HLA-DR matching improves survival after heart transplantation: is it time to change allocation policies?

BACKGROUND: HLA matching has improved outcome in kidney transplantation but is not considered in current allocation policies in heart transplantation. The aim of this single-center study was to assess the impact of HLA matching on long- term outcome after heart transplantation. METHODS: The records of 240 consecutive heart transplant recipients (time period 1995 to 2002; mean age 51.8 +/- 11.7 years; mean follow-up 5.9 +/- 1.8 years) were analyzed retrospectively. According to the renal allocation policy, HLA mismatches (MM) on the major antigen loci HLA-A, HLA-B and HLA-DR were calculated, demonstrating 0 to 6 MM. Patients with primary graft failure were excluded from statistical analysis. RESULTS: Survival analysis revealed a statistically significant impact of HLA-DR MM on survival. Five-year survival was 90% in patients without HLA-DR MM (n = 10), 79% in patients with 1 HLA-DR MM (n = 113), and 68.1% in patients with 2 HLA-DR MM (n = 117) (1 MM vs 2 MM: p < 0.05). Freedom from cardiac allograft vasculopathy after 5 years was 89% in HLA-DR-identical recipients (n = 10), 61% in patients with 1 HLA-DR MM (n = 102), 54% in patients with 2 HLA-DR MM (n = 104). Conventional matching with 6 mismatches over the three major HLA antigen loci revealed a trend toward a higher relative risk for adverse outcome in patients with increased MM. CONCLUSIONS: HLA-DR matching had a significant impact on survival after heart transplantation (HTx) at our center. In the effort to achieve the best comparative use of scarce donor organs the inclusion of HLA-DR matching into allocation policies might improve long-term outcome after HTx.