A tarsal mass removed from a ten year old cat proved to be an extramedullary plasmacytoma largely composed of amyloid. Systemic amyloidosis was indicated when histological examination at necropsy identified amyloid also in the lymph nodes, spleen, and liver. The amyloid subunit protein was isolated by molecular sieve chromatography of reduced and alkylated fibrils extracted from the mass, and its amino acid sequence was determined by sequence analysis of peptides isolated after digestion with trypsin or Staphylococcus protease. The sequence of the C-terminal half of the protein was homologous to the constant region of immunoglobulin lambda light chains of other species establishing the immunoglobulin origin of the amyloid. The N-terminal half of the protein was homologous to the variable region of human lambda light chains and contained several rare residues in the framework regions. To our knowledge, this is the first complete sequence determination of a feline immunoglobulin light chain, and the first complete sequence determination of an amyloid immunoglobulin light chain from a species other than man.
- Extramedullary plasmacytoma
- Immunoglobulin (AL) amyloidosis
- Lambda light chain
ASJC Scopus subject areas
- Pathology and Forensic Medicine