Leukocyte chemotactic factor 2: A novel renal amyloid protein

Renal amyloid deposits can often be seen in primary amyloidosis (immunoglobulin light chain disease) or in secondary forms such as reactive amyloidosis as well as in several hereditary forms where a variety of mutant proteins ‘precipitate’ as amyloid plaques. However, in rare cases, amyloidosis may be identified by renal biopsy, but no definitive diagnosis could be made. We have isolated amyloid fibrils from such a case in which the patient presented with nephrotic syndrome and subsequent azotemia requiring hemodialysis. Evaluation for amyloid deposition in other organ systems was negative and immunohistochemical analysis of the kidney deposits for known contributing proteins was unrevealing. Biochemical analysis of the fibrils identified a new amyloid subunit protein, leukocyte chemotactic factor 2, originally identified as a possible chemotactic and growth factor. A monoclonal antibody to this protein reacted specifically with the amyloid deposits in the glomeruli and interstitium by immunohistochemistry. This study emphasizes the importance of biochemical characterization of amyloid present in renal biopsies.