Immunofluorescence on paraffin to demonstrate monoclonal deposits. A case of light chain deposition disease with kappa light chain restriction. There is nodular mesangial, capillary wall and tubular basement membrane deposition of kappa light chain (A, FITC kappa, × 100) while no deposition of lambda is noted (B, FITC lambda, × 200); C: A case of primary amyloidosis with lambda light chain restriction. The lambda deposition is noted in the mesangium (FITC lambda × 200); D: There is no deposition of kappa (D, FITC kappa × 200); E: A case of cast nephropathy with kappa light chain restriction. Note the brightly positive casts for kappa (FITC kappa × 200) with no traces of lambda (F, FITC lambda × 200). FITC: Fluorescein isothiocyanate.