Lambda III subgroup immunoglobulin light chains are precursor proteins of nodular pulmonary amyloidosis.

To investigate the selectivity of amyloid deposits in lungs, the authors determined the amino-terminal sequence of two amyloid proteins of two nodular pulmonary cases--a case of systemic amyloidosis without myeloma and a localized case--and produced a specific antibody to the amyloid protein of the systemic case to stain other amyloid lung specimens. Moreover, the authors extracted immunoglobulins (Igs) from the amyloidotic spleen of the systemic case to assess their affinity with the lung specimens. Both nodular pulmonary amyloid proteins had an amino-terminal structure similar to that of the lambda III subgroup Ig light chain and reacted with the same antibody. In other cases, nodular forms also stained positively with the same antibody, but interstitial forms were unstained. Extracted Igs containing amyloidogenic lambda III light chains reacted with pulmonary amyloid deposits on sections of both nodular cases. These results suggest that the lambda III subgroup Ig light chains are precursor proteins of nodular pulmonary amyloidosis and that their affinity for pulmonary tissue may be a main determinant of pulmonary localization in nodular amyloidosis.