Peritubular capillary basement membrane multilayering on electron microscopy: a useful marker of early chronic antibody-mediated damage.

BACKGROUND: Chronic antibody-mediated rejection is an important cause of late graft failure. Developing an early marker of the disease may allow diagnosis and treatment before irreversible graft damage has occurred. The aim of this study was to assess whether, on electron microscopy examination, peritubular capillary (PTC) basement membrane multilayering precedes and predicts the development of transplant glomerulopathy (TG). METHODS: We used a vintage matched case-control method. Sixteen case-control pairs were created among all renal transplant patients from October 2005. Cases were patients who developed TG, and controls were patients with a late (>36 months) posttransplant (indication or surveillance) biopsy without TG. Electron microscopy was carried out on a biopsy taken earlier in the posttransplantation period for both cases and controls. RESULTS: For every additional PTC of 25 examined with three or more layers in the early biopsy, the risk of having TG in the later biopsy was increased by 1.4-fold (95% confidence interval, 1.1-1.9; P=0.015). For every PTC of 25 with five or more layers, the risk was increased by 1.6-fold (95% confidence interval, 1.0-2.7; P=0.063). Thus, the risk of future TG increased substantially with every additional PTC of 25 showing multilayering in the early biopsy. CONCLUSIONS: Peritubular capillary basement membrane multilayering on electron microscopy is a useful marker of early chronic antibody-mediated damage, and information can be obtained by assessing PTC with three to four layers of basement membrane in addition to those with five or more layers. This finding must be validated in a prospective study.

Metastatic small cell malignant melanoma: a case requiring immunoelectronmicroscopy for the demonstration of lattice-deficient melanosomes.

A case of metastatic malignant melanoma exhibiting small cell morphology is described. The patient had had a previous primary nodular small cell melanoma. The metastatic tumor was examined by conventional histology, light microscope immunohistochemistry, conventional electron microscopy, and ultrastructural immunolabeling. It consisted of small cells, which, however, varied in size and were present in distinct but merging areas. Tumor cells were negative for S-100 protein and very focally positive for cytokeratin: these findings in combination with small cell morphology suggested the possibility of small cell carcinoma. However, other melanocytic markers were positive. Neuroendocrine markers were negative. By electron microscopy, tumor cells lacked unambiguous melanosomes but contained paranuclear aggregates of nondescript granules. Following ultrastructural immunolabeling, these were found to be decorated with gold-labeled HMB-45 antibodies, thereby confirming them as lattice-deficient melanosomes. This tumor is an uncommon example of malignant melanoma where immunoultrastructural analysis helped clarify the nature of otherwise nondescript granules as true but lattice-deficient melanosomes. This is also the first case of small cell melanoma to be studied by electron microscopy.

The evolution of crescentic nephritis and alveolar haemorrhage following induction of autoimmunity to glomerular basement membrane in an experimental model of Goodpasture's disease.

Goodpasture's, or anti-glomerular basement membrane (GBM), disease presents with rapidly progressive glomerulonephritis and lung haemorrhage, and is caused by autoimmunity to the NC1 domain of the alpha3 chain of type IV collagen (alpha3(IV)NC1). This study examines the development of crescentic nephritis and alveolar haemorrhage in a model of Goodpasture's disease, experimental autoimmune glomerulonephritis (EAG), induced in WKY rats by immunization with rat GBM in adjuvant. An increase in circulating anti-GBM antibodies and albuminuria was observed by week 2, which increased further by weeks 3 and 4, while a decrease in creatinine clearance was observed by week 2, which decreased further by weeks 3 and 4. The kidneys of animals with EAG showed linear deposits of IgG on the GBM and a transient glomerular infiltration by CD4+ T cells at week 2. By week 3 there were large deposits of fibrin in Bowman's space, and glomerular infiltration by CD8+ T cells and macrophages, accompanied by focal necrotizing glomerulonephritis with crescent formation. Ultrastructural studies showed glomerular endothelial cell swelling and epithelial cell foot process effacement at week 2. As the lesion progressed, capillary loops became occluded and the mesangium became expanded by mononuclear cells. By week 3 there was detachment of the endothelium from the GBM, and accumulation of fibrin beneath the disrupted endothelial cells and in Bowman's space. Occasional breaks were observed in the continuity of the basement membrane, and cytoplasmic projections from infiltrating mononuclear cells could be seen crossing the capillary wall between the lumen and the crescent. The lungs of animals with EAG showed patchy binding of IgG to the alveolar basement membrane (ABM) at week 2, and infiltration of the interstitium by CD8+ T cells and macrophages by weeks 3 and 4, accompanied by both interstitial and alveolar haemorrhage. Ultrastructural studies showed focal mononuclear cell infiltrates in alveolar walls at week 2. Occasional breaks were observed in the basement membrane and adjacent endothelium by weeks 3 and 4, together with accumulation of surfactant and erythrocytes within the alveolar spaces. This study defines for the first time the relationship between the immunological and pathological events during the evolution of EAG, and provides the basis for further work on the pathogenesis of Goodpasture's disease.