Long-term evaluation of proliferative donor antigen-specific reactivity in cadaveric kidney transplant recipients

Pre-transplant immune state defined by serum markers and alloreactivity predicts acute rejection after living donor kidney transplantation

Acute rejection (AR) remains a major cause for long-term kidney allograft failure. Reliable immunological parameters suitable to define the pre-transplant immune state and hence the individual risk of graft rejection are highly desired to preferably adapt the immunosuppressive regimen in advance. Donor and third party alloreactivities were determined by mixed lymphocyte cultures. Soluble forms of CD25, CD30, and CD44 were detected in patients' serum by ELISA. Various lymphocyte subpopulations were measured using flow cytometry. All patients received triple immunosuppression (tacrolimus/mycophenolate mofetil/steroids) and were grouped according to biopsy results within the first year: rejection-free (RF, n = 13), borderline (BL, n = 5), or acute rejection (AR, n = 7). Patients with AR showed the highest pre-transplant alloreactivities and serum levels (sCD25/sCD30/sCD44) according to the pattern RF < BL < AR. Relying on serum analysis only, multivariate logistic regression (logit link function) yielded a prognostic score for prediction of rejection with 75.0% sensitivity and 69.2% specificity. Patients with rejection showed markedly higher pre-transplant frequencies of CD4(+) /CD8(+) T cells lacking CD28, but lower numbers of CD8(+) CD161(bright) T cells and NK cells than RF individuals. Pre-transplant immune state defined by alloreactivity, serum markers, and particular lymphocyte subsets seems to correlate with occurrence of graft rejection after kidney transplantation. A prognostic score based on pre-transplant serum levels has shown great potential for prediction of rejection episodes and should be further evaluated.

Detecting adaptive immunity: applications in transplantation monitoring

In recent decades, continuous improvements in immunosuppressive therapy have led to a significant increase in kidney allograft survival. Despite innovative developments and improvements in immunosuppression, chronic allograft injury and late graft loss still remain major causes of morbidity and mortality. In clinical practice, long-term immunosuppression is adapted and fine-tuned according to drug levels, kidney function, and biopsy results. As an invasive procedure, indication biopsy still represents an indispensible diagnostic gold standard. However, in an effort to further improve outcomes on the basis of individualized treatment, there is an urgent need for noninvasive assays, as well as biomarkers, to more accurately monitor allogeneic responses and predict the risk of acute and chronic allograft rejection. This article discusses strategies for immune monitoring of T-cell responsiveness and humoral alloreactivity. Furthermore, new microarray and gene profiling data are highlighted, which may identify hyporesponsive transplant recipients who could benefit from a reduction or even withdrawal of immunosuppression. Finally, supplementary transplant risk assessment markers, such as soluble CD30 and urinary effector molecule analysis, are discussed as promising new tools. Recent developments and improvements in test principles to monitor and predict allograft immunity are encouraging and may herald the transition of present empiric immunosuppression to individualized immunosuppressive treatment. Nonetheless, before implementation of immune monitoring in routine clinical practice, there is still a need for prospective trials designed to clarify the actual diagnostic potential of individual test systems in a therapeutic context.

Improved long-term graft function in kidney transplant recipients with donor antigen-specific hyporeactivity

We investigated the development of donor antigen-specific hyporeactivity by using donor cells as stimulator cells in the MLC and comparing the pre- and post-transplant responses of peripheral blood mononuclear cells. Twenty-two haploidentical pediatric living-relative donor recipients treated with daclizumab, methylprednisone, mofetil mycophenolate and calcineurin inhibitors were tested for study. Of these, 50% of the recipients developed in vitro donor antigen-specific hyporeactivity. The recipients who did so have higher creatinine clearance levels at 12, 24 and 36 months post-transplant (104, 92 and 81 mL/min/1.73 m(2), respectively) than those who remained responsive to donor antigens (77, 74 and 70 mL/min/1.73 m(2)) (p < 0.05). Acute rejection episodes were not observed; however, no recipients with donor-specific hyporeactivity have been diagnosed with CAN, unlike three recipients who remained responsive to donor antigens (0% vs. 27.3%, p = 0.06). Differences in accumulative doses of methylprednisone and mofetil mycophenolate were observed between hyporeactivity- and response-patients to donor antigens at the three years end-point (1.9 +/- 0.8 g/m(2) vs. 4.2 +/- 0.5 g/m(2), and 277 +/- 89 g/m(2) vs. 672 +/- 16.0 g/m(2); p < 0.01 and <0.02, respectively). We conclude that the development of donor antigen-specific hyporeactivity correlate with improved graft function and may permit lower immunosuppression.