Circulating serum amyloid P component is the precursor of amyloid P component in tissue amyloid deposits.

Intravenous administration of 125I-labelled isolated mouse serum amyloid P component (SAP) to mice with systemic amyloidosis was followed by specific deposition of the labelled protein in amyloidotic organs. Although only a small proportion of the total injected dose became localized in this way, the amount correlated with the quantity of amyloid present in different organs and was greatest in the spleen. No such localization was detected in the organs of control, untreated mice or animals which had received inflammatory stimuli but did not have amyloidosis. The labelled SAP was found by autoradiography to be present in the same distribution within the tissues as the Congophilic amyloid deposits. These observations establish directly, for the first time, that circulating SAP is the precursor of the amyloid P component (AP) in systemic amyloidosis. They were confirmed by the further finding that intravenous injection into amyloidotic mice of human SAP, either in whole human serum or in isolated pure form, was followed by appearance of the human SAP in the mouse amyloid deposits. In addition to elucidating one aspect of the pathogenesis of amyloid deposition and strengthening the homology of functional behaviour between SAP of different species, the present results suggest a means for selective targeting of diagnostic tracers and/or effector agents to amyloid deposits in vivo.     

Immunohistological characterisation of amyloid deposits in renal biopsy specimens.

The amyloid deposits in 21 renal biopsy specimens were subjected to a detailed immunohistochemical analysis using a panel of antibodies against recognised constituents of tissue amyloid. This was a retrospective study of material originally submitted during the investigation of various renal abnormalities and studied by a routine protocol including histochemistry, electron microscopy, and immunofluorescence. The presence of an amyloid was confirmed in all 21 cases. Seventeen cases contained P component and either amyloid A (AA) (11 cases) or an immunoglobulin light chain associated amyloid (six cases). Four cases contained amyloid material with unusual immunohistochemical findings; one case had AA and P-component (PC) in the interstitium, one case had lambda light chain and beta-2 microglobulin, one case had kappa light chain and Clq, and one case had lambda light chains only. It was possible, therefore, to identify precisely the amyloid constituents and thereby "type" the amyloid by immunohistochemical means. The availability of the antibodies used and their application using these techniques could simplify the confirmation of clinically suspected amyloidosis.     

Crystal-like deposits of amyloid in pancreatic islet cell tumors.

Numerous stellate crystal-like deposits of amyloid were observed in four human pancreatic islet cell tumors. Three of the tumors were associated with hypoglycemia or hyperinsulinemia, and the remaining one produced gastrin. Histochemical and ultrastructural studies confirmed the existence of amyloid in the deposits and also suggested the presence of adsorbed or incorporated mucopolysaccharides. Stellate amyloid deposits have previously been described in experimental systemic murine amyloidosis. The relationships of these stellate deposits to other forms of amyloid depostion are unknown.     

Nature of amyloid deposits in hypernephroma. Immunocytochemical studies in 2 cases associated with amyloid polyneuropathy.

Two patients who presented with amyloid polyneuropathy were found to have an amyloid-positive hypernephroma. The amyloid extracted from the tumor of one patient was purified by gel filtration and found to immunoreact by immunodiffusion, only with antiserum against denatured lambda-type amyloid protein but not with antisera against denatured kappa amyloid, AA, or prealbumin. With the unlabeled immunoperoxidase method or immunofluorescence in combination with these specific antisera, it was shown that in both patients the amyloid deposits in the tumor, kidney, lymph node, muscle, and nerve had lambda-type amyloid antigenic fibril determinants. Some regions, amyloid-negative by congo red, immunoreacted with anti-lambda antiserum and were shown to represent amyloid fibrils electron microscopically. Several plasma cells found in the tumor and lymph node immunoreacted specifically with the anti-amyloid lambda antiserum. The findings provide the first observation that the amyloid in hypernephroma can be of immunocytic origin, even in the absence of overt signs of plasma cell dyscrasia, and suggest that amyloid polyneuropathy could be the presenting sign of hypernephroma.     

Clinicopathological importance of deposits of amyloid in the femoral head.

The pattern of amyloid deposits in the femoral head is described in four cases, two of which had deposits of amyloid related to age and two of which had generalised systemic amyloidosis (one of primary amyloidosis, one of multiple myeloma). The deposition of amyloid in the articular cartilage of the femoral head was similar in all four cases. Heavy deposits of synovial amyloid were identified in the case with primary amyloidosis and in one of the cases with amyloidosis related to age. Both cases of generalised systemic amyloidosis showed abundant deposits of amyloid in the bone marrow. Amyloid was not present in the bone marrow of either case with amyloidosis related to age. The importance of these findings is discussed in relation to the pathogenesis of the arthropathy syndrome of a rheumatoid type described in cases of primary amyloidosis and multiple myeloma.     

Fine structure and origin of amyloid deposits in pituitary adenoma.

A pituitary adenoma with amyloid deposits was studied by light and electron microscopy. The amyloid material was radially oriented, deposited in the extracellular space, and often intermingled with small vesicles. It was surrounded by histiocytes with deep cytoplasmic invaginations. The histiocytes contained large autophagic vacuoles in which amyloid was also present. These features are similar to other forms of amyloidosis and suggest a histiocytic origin of the amyloid.     

Antibody-mediated resolution of light chain-associated amyloid deposits

Primary light-chain-associated (AL) amyloidosis is characterized by the deposition in tissue of monoclonal light chains as fibrils. With rare exception, this process is seemingly irreversible and results in progressive organ dysfunction and eventually death. To determine whether immune factors can effect amyloid removal, we developed an experimental model in which mice were injected with amyloid proteins extracted from the spleens or livers of patients with AL amyloidosis. Notably, the resultant amyloidomas were rapidly resolved, as compared to controls, when animals received injections of an anti-light-chain monoclonal antibody having specificity for an amyloid-related epitope. The reactivity of this monoclonal antibody was not dependent on the V(L) or C(L) isotype of the fibril, but rather seemed to be directed toward a beta-pleated sheet conformational epitope expressed by AL and other amyloid proteins. The amyloidolytic response was associated with a pronounced infiltration of the amyloidoma with neutrophils and putatively involved opsonization of fibrils by the antibody, leading to cellular activation and release of proteolytic factors. The demonstration that AL amyloid resolution can be induced by passive administration of an amyloid-reactive antibody has potential clinical benefit in the treatment of patients with primary amyloidosis and other acquired or inherited amyloid-associated disorders.     

Development of senile plaques. Relationships of neuronal abnormalities and amyloid deposits.

The evolution of senile plaques and the relationships among neuritic elements, extracellular deposits of the beta-amyloid protein (beta/A4), and vascular beta/A4 are poorly understood. Immunocytochemical methods were used to examine fixed-frozen prefrontal cortices of 14 rhesus monkeys (Macaca mulatta) (14 to 37 years of age) for the presence of abnormal fibers/neurites, alpha 1-antichymotrypsin (alpha-ACT), and beta/A4. Age-associated alterations included abnormal fibers/neurites, presence of beta/A4, and association of alpha-ACT with beta/A4 in plaques and blood vessels. Vascular amyloid was present only in the oldest monkeys. The topographic distribution of abnormal fibers/neurites was mapped with acetylcholinesterase (AChE) histochemistry, and deposits of amyloid were visualized with immunocytochemistry for beta/A4. beta/A4 often was associated with neurites, but many neurites lacked demonstrable beta/A4. Thus in aged monkeys, abnormal neurites may provide one type of focus for the accumulation of the amyloid precursor, which is subsequently abnormally processed to form beta/A4. Our data in rhesus monkeys suggest that fiber and neuritic abnormalities increase with age and that they may precede the majority of beta/A4 deposits; the initial stages of neurite formation and parenchymal amyloid deposits may be independent of the appearance of vascular amyloid; and these processes may be synergistic with advanced age.     

Senile aortic amyloid. Evidence for two distinct forms of localized deposits.

Aortic tissues obtained at autopsy were examined from 84 patients (age, 18-96 years). Amyloid deposits were present in the media in 61 of 63 (97%) of the patients above the age of 50. In addition, intimal amyloid deposits were present in 35% of this group. Intimal amyloid differed from medial amyloid both in its morphologic characteristics and its association with atherosclerosis. An antiserum raised to a low molecular weight protein extracted from amyloid fibrils of the aortic media reacted specifically with medial amyloid but did not react with intimal deposits. Neither type of amyloid reacted with anti-ATTR (Senile systemic amyloid), anti-AANF (isolated atrial amyloid), or antisera to other known forms of amyloid. These findings are consistent with the presence of two separate forms of localized amyloid in the aging aorta.     

The classification of amyloid deposits in clinicopathological practice

A series of 104 biopsy cases with histopathological proof of amyloid, submitted to our department of pathology over the last 19 years, were re-examined. The survey investigated the medical indication for surgery, the origin and quality of the biopsy and the clinical information as documented on the request form for histopathological examination and in hospital records. Amyloid deposits were classified using antisera directed against five major amyloid fibril proteins, i.e. AA, ATTR, Aλ, Aκ and Aβ2M and optimal conditions were sought for the reliable and early characterization of amyloid disease in clinicopathological practice. This survey revealed that 98% of the biopsy cases already suffered from a disease which was either a cause or a result of amyloidosis. In only 2% of the biopsy cases was amyloidosis detected without any clinical indication. Immunohistochemical classification of the amyloid deposits and comparison with hospital records demonstrated diagnostic pitfalls such as immunostaining of amyloid by two or more antibodies recognizing different fibril proteins, and disagreement between immunohistochemical typing of amyloid and the initial clinical diagnosis. Based on these observations we assume that the characterization of amyloid disease and its biological significance is impossible in clinicopathological practice without clinical information or without immunohistochemical classification of the fibril protein in biopsy specimens. Different aspects of histopathological detection of AA- and AL-amyloidosis are discussed.     

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.     

Spheroidal deposits of amyloid in prolactin-secreting pituitary adenomas]

Nine peculiar cases of pituitary adenomas were pointed out by a retrospective investigation at the Ospedale di Legnano (from 1978 to 1984) and at the Ospedale di Circolo di Varese (from 1973 to 1986). These tumours are chromophobe adenomas with diffuse structure. Histologically they show typical, large, spheroid and concentric amyloid deposits, in addition to common, amorphous--often perivascular--ones. They were investigated by histochemical methods (Crystal-Violet, Congo-Red) and by immunohistochemical ones as well (anti-PRL and anti-GH), showing that these deposits are amyloid and are in close relation with PRL production. In particular, by immunohistochemical methods we found out that the cells of the tumours displaying spheroidal bodies do contain prolactin, not GH. The amyloid deposits are also immunohistochemically positive to anti-PRL serum, not to anti-GH serum. Finally, by considering the information present in literature, we have discussed the possible pathogenic mechanisms leading to amyloid deposits in pituitary adenomas.     

Classification of amyloid deposits in diagnostic cardiac specimens by immunofluorescence

BackgroundAt least 12 distinct forms of amyloidosis are known to involve the heart or great vessels. Patient treatment regimens require proper subtyping of amyloid deposits in small diagnostic cardiac specimens. A growing lack of confidence in immunohistochemical staining for subtyping amyloid has arisen primarily as a result of studies utilizing immunoperoxidase staining of formalin-fixed paraffin-embedded tissue. Immunofluorescence staining on fresh frozen tissue is generally considered superior to immunoperoxidase staining for subtyping amyloid; however, this technique has not previously been reported in a series of cardiac specimens.MethodsAmyloid deposits were subtyped in 17 cardiac specimens and 23 renal specimens using an immunofluorescence panel.ResultsAmyloid deposits were successfully subtyped as AL, AH, or AA amyloid by immunofluorescence in 82% of cardiac specimens and 87% of renal specimens. In all cases, the amyloid classification was in good agreement with available clinical and laboratory assessments. A cross-study analysis of 163 cases of AL amyloidosis reveals probable systemic misdiagnosis of cardiac AL amyloidosis by the immunoperoxidase technique, but not by the immunofluorescence technique.ConclusionsAmyloid deposits can be reliably subtyped in small diagnostic cardiac specimens using immunofluorescence. The practical aspects of implementing an immunofluorescence approach are compared with those of other approaches for subtyping amyloid in the clinical setting.