Kidney section analysis of κF-DH mice. (A) Immunofluorescence microscopy on frozen kidney sections of κF-DH mice using anti-mouse κ antibody at 2 and 6 months and humane end point, compared with DH control mice. κLC deposits in κF-DH mice are detectable as soon as age 2 months and become intense with age along tubular and glomerular BMs and in the mesangium. Lesion scores are indicated (see "Methods"). Original magnification ×200. (B) Periodic acid Schiff (PAS) staining performed on paraffin-embedded kidney sections showing tubular BMs thickening and nodular glomerulosclerosis with mesangial expansion of the ECM and mesangial cell proliferation. Note the massive enlargement of glomeruli in κF-DH mice. Original magnification ×200. (C) Electron microscopic analysis showing in left panel linear electron-dense deposits in the inner aspect of the glomerular BM (arrowhead). Subendothelial space is extremely widened, consistent with thrombotic microangiopathy–like lesions (asterisk). Original magnification ×8000. Right panel shows granular electron-dense deposits in the mesangium (arrowhead). Original magnification ×10 000. (D) Immunoelectron microscopy (original magnification ×40 000). Presence of anti-κ gold-conjugated particles along the inner aspect of glomerular BM (arrowhead). All data are representative of at least 3 kidneys in each group.