Nonamyloidotic monoclonal immunoglobulin deposits lack amyloid P component.

Deposits in tissues from 13 patients with amyloid, 8 with monoclonal light chain or light and heavy chain deposition disease, and 2 with both amyloid and nonamyloidotic light chain deposits of the same isotype were examined in parallel for the presence of amyloid P component by immunofluorescence and/or immunoperoxidase methods. Amyloid P component was detected in the amyloid but not the nonamyloid deposits, even in the 2 individuals in whom both types of deposits were present, indicating a specific relationship between the amyloid P component and the amyloid fibrils.