Immunocytological determination of lymphocytes and monocytes/macrophages in urinary sediments of renal allograft recipients

Background. Urinary studies using Papanicolaou staining following kidney transplantation led to the conjecture that acute allograft rejection might be accompanied by an increased lymphocyturia. However, it is difficult to distinguish lymphoid cells from other urinary cells using conventional stains. Methods. Staining of urinary lymphocytes using FITC‐labelled antibodies is complicated by a high unspecific fluorescence that limits the evaluation. Therefore, we developed a method to stain urinary lymphocytes using enzyme‐linked antibodies. The cells were cytocentrifuged onto microscope slides and were fixed. Results. By means of a combined evaluation of Papanicolaou and immunocytochemical staining, CD3‐positive pan T cells, CD4‐positive T‐helper cells, CD8‐positive cytotoxic/suppressor cells, and CD14‐positive monocytes/macrophages of urinary sediments were determined in 41 kidney graft recipients following renal transplantation. During periods of normal graft function, neither positive lymphocytes nor positive monocytes/macrophages were found in the urinary sediments. However, in the course of acute allograft rejection a significant increase in positive lymphocytes and positive monocytes/macrophages could be observed. Interestingly, in cases of acute allograft rejection the distribution of urinary lymphocytes and monocytes was comparable to the distribution of infiltrating immunocompetent cells in renal allograft biopsies. Conclusion. The present study demonstrates that immunocytochemical staining via enzyme‐conjugated antibodies is a reliable method to visualize T lymphocytes and monocytes/macrophages in the urinary sediment, and that this technique may be of special diagnostic value in the diagnosis of acute allograft rejection.