Immunophenotypic analysis of leukocyte infiltration in the renal transplant

Immunohistological analyses of transplant biopsy material can provide valuable insight into the intragraft events following transplantation. The magnitude, composition and phenotype of the leukocyte infiltration and up-regulation of parenchymal antigen expression within the renal allograft have been major areas of interest. Immunohistological analyses have demonstrated the presence of leukocyte infiltration not only during clinical rejection episodes, but also during periods of stable graft function. Nevertheless the infiltration is significantly increased during clinical rejection. Indeed, quantitation of the leukocyte infiltration using a morphometric point counting technique or image analysis can be used prospectively to diagnose rejection in the renal transplant recipient. Macrophages and T lymphocytes (both of the CD4 and CD8 phenotype) are the major infiltrating cells, B lymphocytes and NK cells being present, but in the minority. Activated and proliferating cells have been demonstrated during allograft rejection and may provide a means of identifying a functionally active infiltrate.