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 1 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, 25F9 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, 25F9 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.

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