Ultrastructural immunolabeling in the diagnosis of light-chain-related renal disease.

Renal tissue from eight patients with light-chain deposition disease (LCDD) was immunolabeled for electron microscopy by a postembedding indirect immunogold staining procedure, using anti-kappa and anti-lambda antibodies. This technique provided an exact immunomorphological method to confirm the presence of monotypical light chains in glomeruli, tubules, and vessels. In two cases, it served to prove monotypical light-chain deposition which was not clear upon examination of sections stained for kappa and lambda light chains at the light microscopic level, using PAP or immunofluorescence methods. Three cases of amyloid nephropathy, in which the amyloid deposits stained for monospecific light chains and were immunolabeled ultrastructurally, are also described. LCDD manifests with a variety of morphological patterns in the kidney and the pathological definition of this entity has been difficult. Ultrastructural immunolabeling is a useful method to supplement existing techniques in the diagnosis of LCDD and related conditions. One outstanding feature of the postembedding technique is the ability to examine fixed and preserved renal tissue for the presence of light chains on a retrospective basis.