Medullary nephritis in the diagnosis of acute cellular rejection.

Background: The purpose of this study was to understand the role of lymphomononuclear inflammation (nephritis) in the renal allograft medulla of transplant recipients with acute dysfunction, by comparing the immunophenotype of inflammatory cells present in the medulla and cortex of kidney graft biopsies.

Method: This is a retrospective study of 113 renal allograft needle biopsies, presenting with medullary nephritis, divided into two groups according to the main location of nephritis: in cortical and medullary regions (corticomedullary nephritis) or exclusively in the medullary region (medullary nephritis). We performed immunohistochemistry (IHC) of the cells composing the inflammatory foci, using anti-CD4, CD8, CD20, CD68, and CD138 antibodies, respectively for T-helper cells, cytotoxic T cells, B lymphocytes, macrophages and plasmocytes. The clinical follow-up of the patients was correlated with the morphological findings.

Results: The nephritis was corticomedullary in 66 of the 113 cases (58.4%) and exclusively medullary in the remaining 47 cases (41.6%). The immunophenotype of the inflammatory cells was similar in the cortical and medullary compartments and were mainly: cytotoxic T lymphocytes (CD8) and macrophages CD68. The immunosuppressive therapeutic response to acute cellular rejection (ACR), based on decreasing of serum creatinine values, was 81.8% in the patients of the corticomedullary nephritis group and 63.6% in those of the medullary nephritis group.

Conclusion: Medullary nephritis in renal allograft biopsies may indicate ACR, as could be noted by the immunophenotype, which presented the same cellular mediators of rejection seen in the allograft cortex, and by the positive immunosuppressive therapeutic response observed in most patients.