Histologic and immunophenotypic evaluation of pretreatment renal biopsies in OKT3-treated allograft rejections

The histologic features immunophenotype of intra- graft mononuclear populations, and HLA-Dr expression in pretreatment formalin-fixed renal allograft biopsies were correlated with outcome of OKT3 therapy in 35 steroid resistant renal transplant rejections. Therapeutic response (63% overall) was better in pure acute cellular rejections (ACR) (13/15, 87%) than ACR with interstitial fibrosis (4/12, 33%) or with vascular injury (5/8,62%). Intragraft T lymphocytes were more numerous in vascular rejection (mean 566/mm²) compared with pure ACR (mean 265/mm², P=.049), and macrophages were greater in pure ACR (203/mm²) compared with ACR with interstitial fibrosis (83/mm², P=.051). Distribution of T cells, B cells, plasma cells, and macrophages among various histologic categories was otherwise statistically similar. There was no correlation between therapeutic response to OKT3 and intragraft concentrations of individual mononuclear cell subsets. Vascular and/or epithelial HLA-Dr expression was present in 17/25 (68%) cases and was not associated with histologic features or treatment response. Follow-up graft function (median 7 months) correlated significantly with therapeutic response to OKT3 (P=.0004) and histologic presence of interstitial fibrosis (P=.031), but was not related to concentration of individual mononuclear subsets or HLA-Dr expression. We conclude that intragraft concentrations of major mononuclear cell types may relate to histology, but that these do not predict treatment response or graft outcome, and thus poorly reflect intensity or possible heterogeneity of host immunologic rejection mechanisms.