Electron microscopic peritubular capillary lesions: a new criterion for chronic rejection

Typical chronic rejection showing prominent glomerular and or arterial lesi ons is less common in renal allograft patients treated with cyclosporin A ( CsA). We investigated the value of peritubular capillary lesions as a crite rion for chronic rejection in the CsA era. A total of 129 renal graft biops ies, taken from recipients showing graft dysfunction after mure than 2 mont hs post-operatively, were examined by electron microscopy, and peritubular capillary lesions were studied, especially multi-layered basement membrane lesions (MLPTC). Eighty-two biopsy specimens taken from non-transplantation patients were also studied as a control. Five biopsies (6%) showed mild an d atypical MLPTC in the control group. Of thr 129 allograft biopsies, MLPTC was seen in 55 (42.6%). The prevalence showed no significant relationship to the interval from operation to biopsy. MLPTC was tither typical (n = 10) or incomplete (n = 45). Concomitant membrane disruption, edema and lymphoc yte infiltration of the subendothelial space, reflecting acute cellular rej ection, were occasionally noted in both groups. Incomplete MLPTC often deve loped within 1 yr after surgery in assoc -ciation with acute rejection. it was round in 26-50% of biopsies at any time up to 5 yr post-operatively. Th e incidence of typical MLPTC was 5.7-12.8% over 1 yr post-operatively. Thes e findings suggest that the development of chronic rejection is closely rel ated to relapsing acute tubulo-interstitial allograft rejection which is of ten clinically silent. We concluded that MLPTC is useful as a specific crit erion for chronic rejection.