Clinical leukocyte phenotyping by laser flow cytometry and monoclonal antibodies (immunocytometry) in renal transplantation.

Absolute levels of peripheral blood mononuclear cells were sequentially monitored by immunocytometry in 54 consecutive renal allograft recipients receiving azathioprine/prednisone (STD gp, N = 16) or cyclosporine with or without prednisone (CsA gp, N = 38), before and after transplantation. In the CsA group, but not in those receiving STD therapy, the mean absolute levels of all but OKT4+ cells increased significantly with the duration of therapy. In both treatment groups (STD + CsA), the mean % delta OKT4/8 ratio increased from a prerejection quiescent value of 80 +/- 6% SE to a rejection value of 120 +/- 6% (P less than .001) and fell back to 77 +/- 6% (P less than .0005) in postrejection quiescence. The sensitivity and specificity of such an elevated ratio for rejection were 84.4% and 88.6%, while positive and negative likelihood ratios were 7.40 and 0.15, respectively. In rejection, concomitant immunopathology showed a predominance of OKT8+ cells in the graft with a mean T cell subset ratio of 0.8 +/- 0.3 SE in renal biopsies compared to 2.0 +/- 0.3 for circulating cells (P less than .0125). Parallel donor-antigen-specific assay of lymphocyte-mediated cytotoxicity (LMC) became positive with graft rejection. Immunocytometry with normalization of sequential data in longitudinal analysis thus appears to be a valuable tool in immunologic laboratory monitoring of graft rejection.