Glomerular transplant rejection: a distinctive pattern of early graft damage

Five hundred seventy-six consecutive biopsy or nephrectomy specimens obtained during the first 6 months of transplantation from 300 grafts in 431 recipients were examined by light microscopy for focal or diffuse endocapillary hypercellularity. Forty-seven (8.2%) of the 576 specimens obtained from 37 (12.3%) of the 300 grafts exhibited segmental or global occlusion of capillaries by swollen cells in 40-100% of glomeruli per biopsy. The lesions occurred at any time after transplantation, but 34 (72.3%) were present by day 60 and 7 (14.9%) before day 10. Immunofluorescence in 39 affected biopsies revealed focal or segmental glomerular staining in 18 (46.2%), among which IgM was found most frequently, and was considered to be non-specific. Electron micrographs of 17 biopsies from 14 grafts revealed that glomerular capillaries were narrowed or occluded by mononuclear cells of uncertain type, possibly monocytes, as well as lymphocytes and a few neutrophils. Complement-fixing antibody titers to cytomegalovirus rose at least fourfold in 10 (45.5%) of the 22 patients studied, but glomerular lesions were no more severe in the seroconverters than in the non-converters, and there was no consistent temporal relationship between the occurrence of glomerular changes and seroconversion. Cellular or vascular rejection was present in most biopsies. One year graft survival was 34% among 35 accessed grafts with glomerular lesions, compared to 55% among 243 biopsied grafts with no glomerular changes. We consider that these lesions do not have a consistent association with cytomegalovirus infection and that they represent a distinctive form of glomerular rejection. Whether they indicate a poor graft survival, as the present results suggest but do not prove, requires further studies of other series of cases.