In vitro production of an amyloid-like substance from gamma 3 heavy chain disease protein

Amyloidosis

Amyloidosis is considered rare but has an incidence similar to that of Hodgkin's disease and chronic granulocytic leukemia. The diagnosis should be considered in any patient with unexplained nephrotic-range proteinuria, heart failure, peripheral neuropathy, or hepatomegaly. If a monoclonal protein is found in a patient with any of these clinical presentations, a biopsy should be performed and the specimen stained with Congo red. The simplest source of diagnostic material is subcutaneous fat tissue. Treatment usually consists of chemotherapy, which may be oral and low dose or high dose with stem cell rescue.

Monoclonal immunoglobulin deposition disease: a review of immunoglobulin chain alterations

Monoclonal immunoglobulin deposition disease, a complication of overtly malignant or apparently benign immunoproliferative disorders, is a severe disease featuring tissue deposition of monoclonal light, light and heavy, or heavy chains. A number of converging arguments strongly suggest a direct pathogenetic role of structural abnormalities or peculiarities of variables regions of light and/or heavy chains (associated with deletions in the constant region for the heavy chains). Recent structural data on these abnormal immunoglobulin chains are reviewed.

Immunoglobulin heavy-chain-associated amyloidosis

Immunoglobulin- or multiple myeloma-associated amyloidosis has been distinguished by the tissue deposition of Congophilic, fibrillar protein consisting of light chains or light-chain fragments (AL amyloidosis). We now report the isolation and characterization of another form of immunoglobulin-associated amyloid obtained from a patient who had extensive systemic amyloidosis and in whom the amyloid deposits consisted not of light chains but rather of an unusual form of heavy chain. This component, isolated from splenic amyloid extracts, represented an internally deleted IgG1 heavy chain as evidenced by immunochemical, electrophoretic, and amino acid sequence analyses. A comparable immunoglobulin-related monoclonal protein, consisting only of IgG heavy chains, was present in the patient's urine. Based on serologic reactivity with a battery of anti-immunoglobulin antisera, these two immunoglobulin-related components were antigenically identical; however, when compared to normal IgG, both were deficient in Fc-associated gamma-chain determinants. The structural abnormality of the amyloid gamma-chain protein was further evidenced by SDS/PAGE and immuno-blotting analyses: An unusually low molecular mass of approximately 22 kDa was found for this material vs. the expected value of approximately 55 kDa for a normal gamma heavy chain. Despite the lack of certain Fc determinants, the amyloid and urinary heavy-chain proteins expressed the IgG1 subclass allotype marker G1m(a) located on the third constant region (CH3) domain of the internally deleted IgG1 heavy chains. That the amyloid protein contained an intact CH3 domain was established through amino acid sequence analyses of cyanogen bromide fragments and peptides generated by a lysine-specific protease. These studies also revealed that the gamma-chain amyloid protein contained the complete heavy-chain variable (VH) domain [including the diversity (DH) and joining (JH) segments] that was contiguous with the CH3 domain. The low molecular mass of the protein resulted from the total absence of the first (CH1), hinge, and second (CH2) heavy-chain constant regions. Such extensive CH deletions and the presence of a complete VH distinguish this amyloid-associated heavy chain from all other heretofore characterized gamma-heavy-chain disease proteins. This heavy-chain-related form of immunoglobulin-associated amyloidosis is tentatively designated AH amyloidosis.

Reactive (secondary) amyloidosis and its pathogenesis

Recent advances in amyloid research have broadened our understanding of amyloidogenesis in connection with chronic inflammatory and infectious conditions. Experimental and clinical studies have clarified many of the mechanisms of induction, synthesis and regulation of the amyloid-related serum component SAA and have shed light on the enzymatic processes involved in the cleavage of SAA and degradation of fibrillar AA protein. The current pathogenetic model emphasizes the dynamic character of amyloid disease.

Amyloid typing using antisera to prototype fibril proteins. A brief note

Amyloid fibril proteins from three patients with generalized amyloidosis were isolated and chemically characterized by N-terminal amino-acid sequence studies in two of them. As they belonged to three different amyloid classes they served as prototypes for the preparation of antisera specific for each class. Using these antisera in immunodiffusion, amyloid fibril proteins of 15 additional cases with generalized amyloidosis have been investigated. These could be grouped into four categories: seven belonging to the amyloid A type, three to the amyloid L, lambda type, and three to the amyloid L, kappa type; the amyloid fibril proteins of two patients could not be classified by these agents and may represent still unidentified amyloid types.

Parallel intraylysosomal amyloid fibrils, a possible result of phagocytosis

Vacuoles of mesenchymal cells in the papillae of bovine kidneys with amyloidosis were studied by histochemical electron microscopy for acid phosphatase as a marker for lysosomes. The vacuoles contained parallel amyloid fibrils. The vacuoles of reticular interstitial cells were found to be lysosomes. Vacuoles of macrophage-like cells of the same papillae were positive, partially positive, or negative for the enzyme activity. A suspension of papillary material was injected subcutaneously in rats in a 21-day light and electron microscopy and enzyme histochemistry study. Amyloid was demonstrated in vacuoles of macrophages throughout this period and initially also in neutrophils. In most vacuoles amyloid fibrils were randomly arranged but in others parallel arrangement was demonstrated. Amyloid was only at the inoculation sites. Intralysosomal bovine amyloid may occur in parallel fibrillar arrangement without a definite indication for amyloid production.

The pathogenesis of amyloid deposition: a new hypothesis

Amyloid proteins are probably derived from a variety of precursor glycoproteins. It is postulated that there may be at least two key events in the pathogenesisi of amyloidosis. The first is an increase in the load of glycoprotein being brought to a site of degradation. In the case of myeloma this might be in the form of excess immunoglobulin light chains. In the case of secondary amyloidosis the form taken could be enzyme-alpha-globulin complexes. The second is an inability of the degrading site to handle the arriving substrate at a sufficiently rapid rate, the rate limiting step being at some point along the degradation pathway. We postulate that an acquired enzyme deficiency prevents removal of the carbohydrate moiety of the presented glycoprotein. This results in the accumulation of a normal intermediate (amyloid protein) during the breakdown of the glycoprotein substrate. Evidence for the operation of these mechanisms is discussed and their detailed nature and implications considered.