B cells and rejection: is there a link? Meaning and management of rejection characterized by steroid-resistance and B-cell infiltrates

Blood biomarkers of kidney transplant rejection, an endless search?

INTRODUCTION

The tailoring of immunosuppressive treatment is recognized as a promising strategy to improve long-term kidney graft outcome. To guide the standard care of transplant recipients, physicians need objective biomarkers that can identify an ongoing pathology with the graft or low intensity signals that will be later evolved to accelerated transplant rejection. The early identification of 'high-risk /low-risk' patients enables the adjustment of standard of caring, including managing the frequency of clinical visits and the immunosuppression dosing. Given their ease of availability and the compatibility with a large technical array, blood-based biomarkers have been widely scrutinized for use as potential predictive and diagnostic biomarkers. Areas covered: Here, the authors report on non-invasive biomarkers, such as modification of immune cell subsets and mRNA and miRNA profiles, identified in the blood of kidney transplant recipients collected before or after transplantation. Expert commentary: Combined with functional tests, the identification of biomarkers will improve our understanding of pathological processes and will contribute to a global improvement in clinical management.

Peripheral blood biomarkers for the characterization of alloimmune reactivity after pediatric liver transplantation

Individualization of immunosuppressive medications is an important objective in transplantation medicine. Reliable biomarkers to distinguish between patients dependent from intensive immunosuppressive therapy and those where therapy can be minimized among pediatric transplant recipients receiving immunosuppressive medications are still not established. We evaluated the potential of cross-sectional quantification of regulatory T cells, lymphocyte subsets, and cytokine concentrations as biomarkers in 60 pediatric liver transplant recipients with AR, CR, or normal graft function and in 11 non-transplanted patients. Transplant recipients presenting with AR had significantly higher CD8+ T-cell counts, significantly higher concentrations of IL-2, and increased levels of IFN-γ compared with asymptomatic patients or controls. Regulatory T-cell numbers did not differ between children with rejection and children with good graft function. A tendency toward increased concentrations of IL-4 and TGF-β was detected in transplant recipients with good graft function. Cross-sectional parameters of peripheral regulatory T cells in pediatric liver transplant recipients do not seem to be valuable biomarkers for individualizing immunosuppressive therapy prior to the weaning process. Lymphocyte subsets, IL-2, IFN-γ, IL-4, and TGF-β serum concentrations may be helpful to identify children in whom immunosuppression can be reduced or discontinued.

Significance of intragraft CD138+ lymphocytes and p-S6RP in pediatric kidney transplant biopsies

BACKGROUND

We have previously shown that intragraft CD20+ B cells are associated with acute cellular rejection (ACR) and allograft loss. Phosphorylation of S6 ribosomal protein, a downstream target of the PI3K/Akt/mTOR pathway, promotes growth and proliferation of cells and could identify metabolically active cells such as alloantibody secreting plasma cells. Because CD20+ lymphocytes can differentiate into CD138+ plasma cells, we aimed to identify functionally active plasma cells by using intragraft CD138 quantification and p-S6RP staining and correlate these results with allograft rejection, function, and survival.

METHODS

We examined 46 renal transplant biopsies from 32 pediatric patients who were biopsied for clinical suspicion of rejection. Immunohistochemical staining for C4d, CD20, CD138, and p-S6RP was performed. Patient creatinine clearance and graft status was followed up postbiopsy.

RESULTS

Patients with greater than or equal to six CD138+ cells/high power field (hpf) had worse graft survival with a hazard ratio of 3.4 (95% CI 1.3-9.2) 2 years postbiopsy compared with those with 0 to 5 cells/hpf (P=0.016). CD138+ cells were stained for p-S6RP, indicating functionally active plasma cells. They were associated with ACR (P=0.004) and deteriorating graft function (R=0.22, P=0.001). Intragraft CD20+ and CD138+ cells found together in ACR were associated with poorer graft survival than either marker alone, hazard ratio 1.5 (95% CI 1.1-2.2, P=0.01).

CONCLUSIONS

A threshold of greater than or equal to six CD138+ metabolically active plasma cells per hpf, coexisting with CD20+ B cells, was associated with poor allograft function and survival. This may represent an additional antibody-mediated process present in the setting of ACR and could play an important role in characterization and treatment of transplant rejection.