Early infiltration of renal allografts with 27E10‐positive macrophages and graft outcome

Recently, we have demonstrated that acute cellular rejection is correlated with a massive infiltration of 27E10‐positive macrophages. To examine the distribution of macrophage differentiation markers in the infiltrate in the very early post‐transplantation period, two biopsies were taken intraoperatively, approximately 3 h following reperfusion, in each of 16 renal transplant recipients. One biopsy was taken for conventional histology and the other biopsy was snap‐frozen. The sections were stained using an ABC indirect immunoperoxidase technique. A panel of monoclonal antibodies against three macrophage differentiation markers (27E10, 25 F 9 and RM3/1) was used to stain the sections. Using the early inflammation macrophage marker 27E10, there was an unexpected strong staining in 3 out of 16 biopsies. This severe infiltration of 27E10‐positive macrophages with 10–20 macrophages per high power field (compared to 0–2 in others) was correlated in all cases with a poor outcome of the graft. All seven kidneys with no 27E10‐positive infiltration showed a good function 6 weeks post‐transplantation. The other macrophage markers, 25 F 9 and RM3/1, showed a less marked correlation with graft outcome. In conclusion, a massive infiltration of renal allografts with 27E10‐positive macrophages 1 h post‐transplantation may be a very early predictor of poor graft outcome.