Serum amyloid A protein in amyloidosis, rheumatic, and enoplastic diseases

Lung cancer combined with diffuse peritoneal and mesenteric amyloidosis detected on 18F-FDG PET/CT: A case report

RATIONALE

Amyloidosis is a heterogeneous group of diseases characterized by extracellular deposition of amyloid fibrils. Lung carcinoma is rarely reported to be associated with AA amyloidosis. With regard to the manifestation of amyloidosis infiltrating organs, most of the cases focus on the heart, liver, kidneys, and peripheral nervous system. Amyloidosis with diffuse abdominal involvement in combination with pulmonary squamous cell carcinoma carcinoma is an exceptionally rare occurrence.

PATIENT CONCERNS

A 70-year-old man was admitted to hospital for a 2-month history of repeated cough, low grade fever, hemoptysis and left back shoulder pain, which was not relieved by nonsteroid anti-inflammatory drugs. Meanwhile, he complained of intermittent diffuse abdominal discomfort and chronic persistent constipation.

DIAGNOSES

The patient was diagnosed with poorly differentiated lung squamous cell carcinoma and diffuse peritoneal and mesenteric amyloidosis based on the pathological biopsy.

INTERVENTIONS

The patient received surgery and chemotherapy for lung tumor. He did not receive any treatment against amyloidosis.

OUTCOMES

The patient died of a severe respiratory infection.

LESSONS

This case indicates that lung carcinoma is suspected to play a causative role in the development of amyloidosis. In addition, amyloidosis should be considered in the differential diagnosis in cases in which diffuse greater omentum, peritoneal, and mesenteric calcifications on 18F-2-fluoro-2-deoxy-D-glucose(18F-FDG) photon emission computed tomography (PET/CT).

Serum Amyloid A in Inflammatory Rheumatic Diseases: A Compendious Review of a Renowned Biomarker

Serum amyloid A (SAA) is an acute phase protein with a significant importance for patients with inflammatory rheumatic diseases (IRD). The central role of SAA in pathogenesis of IRD has been confirmed by recent discoveries, including its involvement in the activation of the inflammasome cascade and recruitment of interleukin 17 producing T helper cells. Clinical utility of SAA in IRD was originally evaluated nearly half a century ago. From the first findings, it was clear that SAA could be used for evaluating disease severity and monitoring disease activity in patients with rheumatoid arthritis and secondary amyloidosis. However, cost-effective and more easily applicable markers, such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), overwhelmed its use in clinical practice. In the light of emerging evidences, SAA has been discerned as a more sensitive biomarker in a wide spectrum of IRD, especially in case of subclinical inflammation. Furthermore, a growing number of studies are confirming the advantages of SAA over many other biomarkers in predicting and monitoring response to biological immunotherapy in IRD patients. Arising scientific discoveries regarding the role of SAA, as well as delineating SAA and its isoforms as the most sensitive biomarkers in various IRD by recently developing proteomic techniques are encouraging the revival of its clinical use. Finally, the most recent findings have shown that SAA is a biomarker of severe Coronavirus disease 2019 (COVID-19). The aim of this review is to discuss the SAA-involving immune system network with emphasis on mechanisms relevant for IRD, as well as usefulness of SAA as a biomarker in various IRD. Therefore, over a hundred original papers were collected through an extensive PubMed and Scopus databases search. These recently arising insights will hopefully lead to a better management of IRD patients and might even inspire the development of new therapeutic strategies with SAA as a target.

Variation of amino acid sequences of serum amyloid a (SAA) and immunohistochemical analysis of amyloid a (AA) in Japanese domestic cats

Amyloid A (AA) amyloidosis, a fatal systemic amyloid disease, occurs secondary to chronic inflammatory conditions in humans. Although persistently elevated serum amyloid A (SAA) levels are required for its pathogenesis, not all individuals with chronic inflammation necessarily develop AA amyloidosis. Furthermore, many diseases in cats are associated with the elevated production of SAA, whereas only a small number actually develop AA amyloidosis. We hypothesized that a genetic mutation in the SAA gene may strongly contribute to the pathogenesis of feline AA amyloidosis. In the present study, genomic DNA from four Japanese domestic cats (JDCs) with AA amyloidosis and from five without amyloidosis was analyzed using polymerase chain reaction (PCR) amplification and direct sequencing. We identified the novel variation combination of 45R-51A in the deduced amino acid sequences of four JDCs with amyloidosis and five without. However, there was no relationship between amino acid variations and the distribution of AA amyloid deposits, indicating that differences in SAA sequences do not contribute to the pathogenesis of AA amyloidosis. Immunohistochemical analysis using antisera against the three different parts of the feline SAA protein—i.e., the N-terminal, central, and C-terminal regions—revealed that feline AA contained the C-terminus, unlike human AA. These results indicate that the cleavage and degradation of the C-terminus are not essential for amyloid fibril formation in JDCs.

Experimental induction of chicken amyloid A amyloidosis in white layer chickens by inoculation with inactivated vaccines

We investigated the amyloidogenic potential of inactivated vaccines and the localized production of serum amyloid A (SAA) at the injection site in white layer chickens. Hens in the treated group were injected intramuscularly three times with high doses of inactivated oil-emulsion Salmonella Enteritidis vaccine and multivalent viral and bacterial inactivated oil-emulsion vaccines at two-week intervals. Chickens in the control group did not receive any inoculum. In the treated group, emaciation and granulomas were present, while several chickens died between 4 and 6 weeks after the first injection. Hepatomegaly was seen at necropsy, and the liver parenchyma showed inconsistent discolouration with patchy green to yellowish-brown areas, or sometimes red-brown areas with haemorrhage. Amyloid deposition in the liver, spleen, duodenum, and at injection sites was demonstrated using haematoxylin and eosin staining, Congo red, and immunohistochemistry. The incidence of chicken amyloid A (AA) amyloidosis was 47% (28 of 60) in the treated group. In addition, RT-PCR was used to identify chicken SAA mRNA expression in the liver and at the injection sites. Furthermore, SAA mRNA was detected by in situ hybridization in fibroblasts at the injection sites, and also in hepatocytes. We believe that this is the first report of the experimental induction of systemic AA amyloidosis in white layer chickens following repeated inoculation with inactivated vaccines without the administration of amyloid fibrils or other amyloid-enhancing factors.

Feline serum amyloid A protein as an endogenous Toll-like receptor 4 agonist

Serum amyloid A (SAA) is one of the major acute phase proteins and a biomarker of infection or inflammation in humans and cats. In humans, cytokine-like functions of SAA protein have been determined, and SAA is considered to be an important factor in immune responses. However, there are no reports about the functions of SAA protein in cats. In the present study, the functions of feline SAA protein on peripheral monocytes were investigated by using TNF-α production as an indicator. In feline peripheral blood monocytes, SAA protein stimulated the transcription of TNF-α within 2h and induced TNF-α secretion in time- and dose-dependent manners. The production of TNF-α by SAA stimulation in feline monocytes was found to be mediated by the activation of nuclear factor-kappa B (NF-κB). Moreover, SAA-stimulated TNF-α production was prevented by a Toll-like receptor 4 (TLR4) antagonist. On the basis of these results, feline SAA was demonstrated to be an endogenous agonist of TLR4 for the stimulation of TNF-α production and secretion by peripheral monocytes. These results suggest that feline SAA can play an important role in the regulation of inflammation and immune responses as it does in humans.

Determination of inflammatory biomarkers in patients with COPD: a comparison of different assays

Background

Chronic obstructive pulmonary disease (COPD) is an inflammatory pulmonary disorder with systemic inflammatory manifestations that are mediated by circulating acute-phase reactants. This study compared an enzyme-linked immunosorbent assay (ELISA) to a nephelometric technique for the measurement of serum C-reactive protein (CRP) and serum amyloid A (SAA) and investigated how the choice of assay influenced the estimation of inflammation in patients with stable COPD.

Methods

CRP and SAA concentrations measured by ELISA and nephelometry in 88 patients with COPD and 45 control subjects were used to evaluate the performance of these methods in a clinical setting.

Results

With both assays, the concentrations of CRP and SAA were higher in COPD patients than in controls after adjustment for age and sex. There was a moderate correlation between the values measured by ELISA and those measured by nephelometry (logCRP: r = 0.55, p < 0.001; logSAA: r = 0.40, p < 0.001). However, the concentrations of biomarkers determined by nephelometry were significantly higher than those obtained with ELISA for CRP (mean difference = 2.7 (9.4) mg/L) and SAA (mean difference = 0.31 (14.3) mg/L).

Conclusion

Although the serum CRP and SAA concentrations measured by ELISA and nephelometry correlated well in COPD patients, the ELISA values tended to be lower for CRP and SAA when compared with nephelometric measurements. International standardization of commercial kits is required before the predictive validity of inflammatory markers for patients with COPD can be effectively assessed in clinical practice.

Cyclooxygenase-2 -765G>C polymorphism is associated with C-reactive protein levels in resistant smokers but not in chronic obstructive pulmonary disease patients

We sought to investigate whether the serum concentrations of several inflammatory biomarkers are related to the cyclooxygenase-2 (COX2) -765G>C polymorphism in chronic obstructive pulmonary disease (COPD) and a control group of non-COPD smokers. Serum inflammatory markers (CRP, SAA, CXCL8, and sICAM-1) were measured by ELISA in 144 patients with COPD and in 55 control subjects. Genomic DNA was extracted from peripheral blood leukocytes, and the COX2 -765G>C (rs20417) polymorphism was genotyped. After adjustment for age and active smoking, CRP and SAA concentrations were associated with the COX2 polymorphism in controls (p=0.041 and 0.014, respectively) but not in COPD patients. The CXCL8 and sICAM-1 concentrations were not associated with the COX2 polymorphism for either cases or controls. The results of the present study indicate that there is a relationship between the COX2 -765G>C polymorphism and the concentrations of CRP and SAA in non-COPD smokers and that this relationship does not exist in COPD patients.

Identification and validation of SAA as a potential lung cancer biomarker and its involvement in metastatic pathogenesis of lung cancer

Lung cancer is recently regarded as an overhealed inflammatory disease. Serum amyloid A (SAA) is known as an acute phase protein, but it is likely involved in the cancer pathogenesis. We identified both SAA1 and SAA2 in the pooled sera of lung cancer patients but not in the healthy control, by LC-MS/MS analysis. We found that about 14-fold higher levels of SAA in lung cancer patients' sera and plasma compared to healthy controls by ELISA using total 350 samples (13.89 ± 37.18 vs 190.49 ± 234.70 ug/mL). The SAA levels were also significantly higher than in other pulmonary disease or other cancers. An immunohistochemical study using tissue microarray showed that, unlike other cancer tissues, lung cancer tissues highly express SAA. Further in vitro experiments showed that SAA is induced from lung cancer cells by the interaction with THP-1 monocytes and this, in return, induces MMP-9 from THP-1. In in vivo animal models, overexpressed SAA promoted Lewis lung carcinoma (LLC) cells to metastasize and colonize in the lung. Our data suggest that a higher concentration of SAA can serve as an indicator of lung adenocarcinoma and represents a therapeutic target for the inhibition of lung cancer metastasis.

Oral involvement in a case of AA amyloidosis: a case report

Introduction

Deposition of amyloid fibrils derived from circulating acute-phase reactant serum amyloid A protein causes systemic amyloidosis, a serious inflammatory disorder. We document a male patient who developed reactive amyloidosis (AA type), most likely secondary to his long standing periodontitis.

Case presentation

A 67-year-old Turkish man complained of pain in his oral cavity (burning mouth) especially on the tongue, and had difficulty chewing and swallowing foods. A careful dental/periodontal examination was performed, including assessment of plaque, gingival condition and periodontal probing depths on all his remaining teeth. Prosthetic rehabilitation was provided three months after the completion of his periodontal and surgical therapy. The concentration of serum inflammatory markers including erythrocyte sedimentation rate, white blood cell count, fibrinogen and high sensitive C-reactive protein were measured at baseline, at the second and sixth weeks, and at three and six months after the periodontal and surgical therapy.

Conclusions

Oral examination revealed a few papules on the dorsum of the tongue with two slightly painful, small ulcers, localized on the vestibule of the mouth. The mean probing depth was 9.10 ± 0.84 mm. Biopsies of the tongue, buccal mucosa and retromolar trigone were performed and amyloid deposits were found. The serum inflammatory markers improved more dramatically at the second week of periodontal therapy than any other time intervals.

Amyloidosis may manifest as periodontal destruction that leads to severe chronic periodontitis. Proper periodontal treatment may alleviate systemic inflammatory mediators caused by the amyloidosis.

CD36 is a novel serum amyloid A (SAA) receptor mediating SAA binding and SAA-induced signaling in human and rodent cells

Serum amyloid A (SAA) is a major acute phase protein involved in multiple physiological and pathological processes. This study provides experimental evidence that CD36, a phagocyte class B scavenger receptor, functions as a novel SAA receptor mediating SAA proinflammatory activity. The uptake of Alexa Fluor 488 SAA as well as of other well established CD36 ligands was increased 5-10-fold in HeLa cells stably transfected with CD36 when compared with mock-transfected cells. Unlike other apolipoproteins that bind to CD36, only SAA induced a 10-50-fold increase of interleukin-8 secretion in CD36-overexpressing HEK293 cells when compared with control cells. SAA-mediated effects were thermolabile, inhibitable by anti-SAA antibody, and also neutralized by association with high density lipoprotein but not by association with bovine serum albumin. SAA-induced cell activation was inhibited by a CD36 peptide based on the CD36 hexarelin-binding site but not by a peptide based on the thrombospondin-1-binding site. A pronounced reduction (up to 60-75%) of SAA-induced pro-inflammatory cytokine secretion was observed in cd36(-/-) rat macrophages and Kupffer cells when compared with wild type rat cells. The results of the MAPK phosphorylation assay as well as of the studies with NF-kappaB and MAPK inhibitors revealed that two MAPKs, JNK and to a lesser extent ERK1/2, primarily contribute to elevated cytokine production in CD36-overexpressing HEK293 cells. In macrophages, four signaling pathways involving NF-kappaB and three MAPKs all appeared to contribute to SAA-induced cytokine release. These observations indicate that CD36 is a receptor mediating SAA binding and SAA-induced pro-inflammatory cytokine secretion predominantly through JNK- and ERK1/2-mediated signaling.

Serum amyloid A: an acute-phase protein involved in tumour pathogenesis

The synthesis of acute-phase protein serum amyloid A (SAA) is largely regulated by inflammation- associated cytokines and a high concentration of circulating SAA may represent an ideal marker for acute and chronic inflammatory diseases. However, SAA is also synthesized in extrahepatic tissues, e.g. human carcinoma metastases and cancer cell lines. An increasing body of in vitro data supports the concept of involvement of SAA in carcinogenesis and neoplastic diseases. Accumulating evidence suggests that SAA might be included in a group of biomarkers to detect a pattern of physiological events that reflect the growth of malignancy and host response. This review is meant to provide a broad overview of the many ways that SAA could contribute to tumour development, and accelerate tumour progression and metastasis, and to gain a better understanding of this acute-phase reactant as a possible link between chronic inflammation and neoplasia.

Periodontal disease in patients with familial Mediterranean fever: from inflammation to amyloidosis

BACKGROUND AND OBJECTIVE

Familial Mediterranean fever stimulates a very intense acute-phase reactants response and if left untreated eventually leads to amyloidosis. The aim of this study was to determine the prevalence of periodontal disease among patients with familial Mediterranean fever in the Black Sea region in Turkey and to evaluate whether periodontitis is related to amyloidosis in patients with familial Mediterranean fever.

MATERIAL AND METHODS

One-hundred and thirty three patients with familial Mediterranean fever and 50 healthy subjects were included in this study. Periodontal health and disease were evaluated using the gingival index, papillary bleeding index, plaque index and periodontal disease index. The concentrations of serum acute-phase reactants were measured at baseline and at 4-6 wk after completion of the nonsurgical periodontal therapy. Genetic testing for familial Mediterranean fever was performed using the familial Mediterranean fever StripAssay. Kidney biopsy was carried out on all proteinuric patients.

RESULTS

The prevalence of moderate to severe periodontitis in familial Mediterranean fever patients with amyloidosis (80.6%) was significantly greater (p < 0.01) than in familial Mediterranean fever patients without amyloidosis (38%) and in controls (20%). Serum levels of acute-phase reactants in familial Mediterranean fever patients were reduced significantly following nonsurgical periodontal therapy (p < 0.01).

CONCLUSION

Periodontal therapy seems to reduce the serum levels of acute-phase reactants in patients with familial Mediterranean fever. Therefore, treating periodontitis might help to alleviate the disease burden in patients with familial Mediterranean fever.

Serum proteome analysis for profiling protein markers associated with carcinogenesis and lymph node metastasis in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC), one of the most common cancers in population with Chinese or Asian progeny, poses a serious health problem for southern China. It is unfortunate that most NPC victims have had lymph node metastasis (LNM) when first diagnosed. We believe that the 2D based serum proteome analysis can be useful in discovering new biomarkers that may aid in the diagnosis and therapy of NPC patients. To filter the tumor specific antigen markers of NPC, sera from 42 healthy volunteers, 27 non-LNM NPC patients and 37 LNM NPC patients were selected for screening study using 2D combined with MS. Pretreatment strategy, including sonication, albumin and immunoglobulin G (IgG) depletion, was adopted for screening differentially expressed proteins of low abundance in serum. By 2D image analysis and MALDI-TOF-MS identification, twenty-three protein spots were differentially expressed. Three of them were further validated in the sera using enzyme-linked immunosorbent assay (ELISA). Our research demonstrates that HSP70, sICAM-1 and SAA, confirmed with ELISA at sera and immunohistochemistry, are potential NPC metastasis-specific serum biomarkers which may be of great underlying significance in clinical detection and management of NPC.

The value of the levels of acute phase reactants for the prediction of familial Mediterranean fever associated amyloidosis: a case control study

In order to determine the role of levels of acute phase proteins (APPs) for the development of amyloidosis in familial Mediterranean fever (FMF) patients, the levels of serum amyloid A (SAA), C reactive protein (CRP), fibrinogen and erythrocyte sedimentation rate were measured in paired sera of 36 FMF patients during and in between acute attacks, 39 of their healthy parents (obligate heterozgotes), and 15 patients with FMF associated amyloidosis. To compare the levels of APPs, 39 patients with chronic infections or inflammatory diseases who may develop secondary amyloidosis, 20 patients with acute infections who are known to have elevated acute phase response but will never develop amyloidosis and 19 healthy controls were included. The median levels of all APPs are increased in the patients with FMF during attacks and a significant decrease was observed after the attack was over. The level of SAA was above reference range in all FMF patients during the attack free period and the level of at least one other APP was also above normal in 64% of the patients. Both CRP and SAA levels were found to be higher in obligate heterozygotes compared to controls. The levels of SAA in patients with FMF during the attack-free period, obligate heterozygotes and patients with FMF-amyloidosis were found to be similar. The levels in each group were found to be higher than SAA levels found in healthy controls yet lower than the levels measured in the patients with acute infections and patients with chronic inflammation or chronic infections. In conclusion, our results show that SAA level reflects subclinical inflammation with high sensitivity but its value for the prediction of amyloid formation process seems to be low.

Serum amyloid A (SAA) protein and high-sensitivity C-reactive protein (hsCRP) in healthy newborn infants and healthy young through elderly adults

AIM

To determine the levels of serum amyloid A (SAA) protein and high-sensitivity C-reactive protein (hsCRP) in different age groups.

METHODS

Serum samples from 70 healthy newborn infants, 80 blood donors and 81 healthy elderly individuals were analysed using a nephelometric method. The 231 samples were grouped as follows: 35 umbilical cords, 35 newborns, 48 young adults, 28 middle-aged adults, and 85 elderly adults.

RESULTS

Serum levels of both SAA and hsCRP were lower in umbilical cords than in the newborns and young, middle-aged and elderly adults (p<0.0001). The SAA and hsCRP levels were comparable in newborns, and young and middle-age adults, but higher in elderly adults (p<0.0001-0.03). SAA (r2=0.159, p<0.0001) and hsCRP (r2=0.059, p<0.0001) were positively correlated with age and to each other (r2=0.385, p<0.0001).

CONCLUSION

Serum levels of SAA and hsCRP in umbilical cord blood are close to the detection limit and lower than in the other age groups investigated. The elderly have generally higher levels than the younger age groups, which require higher decision levels in inflammatory diseases, including infections. In newborns and young and middle-aged adults, the lower decision levels of 10 mg/l for SAA and 5 mg/l for CRP are suggested.

Distinctive serum protein profiles involving abundant proteins in lung cancer patients based upon antibody microarray analysis

Background

Cancer serum protein profiling by mass spectrometry has uncovered mass profiles that are potentially diagnostic for several common types of cancer. However, direct mass spectrometric profiling has a limited dynamic range and difficulties in providing the identification of the distinctive proteins. We hypothesized that distinctive profiles may result from the differential expression of relatively abundant serum proteins associated with the host response.

Methods

Eighty-four antibodies, targeting a wide range of serum proteins, were spotted onto nitrocellulose-coated microscope slides. The abundances of the corresponding proteins were measured in 80 serum samples, from 24 newly diagnosed subjects with lung cancer, 24 healthy controls, and 32 subjects with chronic obstructive pulmonary disease (COPD). Two-color rolling-circle amplification was used to measure protein abundance.

Results

Seven of the 84 antibodies gave a significant difference (p < 0.01) for the lung cancer patients as compared to healthy controls, as well as compared to COPD patients. Proteins that exhibited higher abundances in the lung cancer samples relative to the control samples included C-reactive protein (CRP; a 13.3 fold increase), serum amyloid A (SAA; a 2.0 fold increase), mucin 1 and α-1-antitrypsin (1.4 fold increases). The increased expression levels of CRP and SAA were validated by Western blot analysis. Leave-one-out cross-validation was used to construct Diagonal Linear Discriminant Analysis (DLDA) classifiers. At a cutoff where all 56 of the non-tumor samples were correctly classified, 15/24 lung tumor patient sera were correctly classified.

Conclusion

Our results suggest that a distinctive serum protein profile involving abundant proteins may be observed in lung cancer patients relative to healthy subjects or patients with chronic disease and may have utility as part of strategies for detecting lung cancer.

Identification of Serum Amyloid A Protein As a Potentially Useful Biomarker to Monitor Relapse of Nasopharyngeal Cancer by Serum Proteomic Profiling

PURPOSE

Nasopharyngeal cancer (NPC) is a common cancer in Hong Kong, and relapse can occur frequently. Using protein chip profiling analysis, we aimed to identify serum biomarkers that were useful in the diagnosis of relapse in NPC.

EXPERIMENTAL DESIGN

Profiling analysis was performed on 704 sera collected from 42 NPC patients, 39 lung cancer patients, 30 patients with the benign metabolic disorder thyrotoxicosis (TX), and 35 normal individuals (NM). Protein profile in each NPC patient during clinical follow up was correlated with the relapse status.

RESULTS

Profiling analysis identified two biomarkers with molecular masses of 11.6 and 11.8 kDa, which were significantly elevated in 22 of 31 (71%) and 21 of 31 (68%) NPC patients, respectively, at the time of relapse (RP) as compared with 11 patients in complete remission (CR; RP versus CR, P = 0.009), 30 TX (RP versus TX, P < 0.001), or 35 NM (RP versus NM, P < 0.001). The markers were also elevated in 16 of 39 (41%) lung cancer patients at initial diagnosis. By tryptic digestion, followed by tandem mass spectrometry fragmentation, the markers were identified as two isoforms of serum amyloid A (SAA) protein. Monitoring the patients longitudinally for SAA level both by protein chip and immunoassay showed a dramatic SAA increase, which correlated with relapse and a drastic fall correlated with response to salvage chemotherapy. Serum SAA findings were compared with those of serum Epstein-Barr virus DNA in three relapsed patients showing a similar correlation with relapse and chemo-response.

CONCLUSIONS

SAA could be a useful biomarker to monitor relapse of NPC.

Serum amyloid a in clinical practice

Serum amyloid A (SAA) is an acute phase first class protein discovered a quarter of the century ago. Its concentration depends on clinical findings of the patient, illness activity and the therapy applied. SAA increases moderately to markedly (100-1000 mg/l) in bacterial and fungal infections, invasive malignant diseases, tissue injuries in the acute myocardial infarction and autoimmune diseases such as rheumatoid arthritis and vasculitis. Mild elevation (10-100 mg/l) is often seen in viral infections, systemic lupus erythematosus and localized inflammation or tissue injuries in cystitis and cerebral infarction. SAA as sensitive, non-invasive parameter is used in organ transplantation where early and correct diagnosis is needed as well as where prompt therapy is required. Besides acute kidney allograft rejection, SAA is used in the diagnosis of rejection after liver transplantation, simultaneous pancreas and kidney transplantation and also in bone marrow transplantation (acute ?graft vs. host disease"). Simultaneous determination of C-reactive protein (CRP) and SAA may point to acute kidney allograft rejection. Standard immunosuppressive therapy with cyclosporine A and prednisolone significantly suppresses the acute phase CRP reaction both in operation itself and acute rejection, but not in infection. On the other hand, SAA rejection in operation, acute allograft rejection and infection is present in spite of cyclosporine A and steroids therapy. Different reaction of SAA and CRP in transplant patients to cyclosporine A therapy helps in differentiation between the infection and rejection. Although CRP and SAA are sensitive and acute phase reactants, their serum concentrations cannot be valued as prognostic and diagnostic criteria without creatinine serum concentration and clinical findings. In addition, they offer important information for clinical diagnosis as well as the kind of therapy.

Amyloidosis and Lung Cancer

Clinical systemic amyloidosis has been rarely described in patients with lung cancer. A new case of such an association is described with a review of the literature and a discussion about the possible biological mechanisms responsible for the development of systemic amyloidosis in patients with lung cancer. Circulating precursors of amyloid fibrils in patients with lung cancer might be implicated more than expected in the biology of tumoral disease.

C-reactive protein and serum amyloid A protein in neonatal infections

In this study, we examine C-reactive protein (CRP) and serum amyloid protein A (SAA). Although the former is the best known and most commonly used indicator of inflammation, certain considerations underline the inadequacy of CRP determination alone for the early diagnosis of infection. In fact symptoms often precede the CRP elevation. SAA protein comprises a family of polymorphic apolipoproteins produced mainly by the liver, and several studies have stressed its importance in the diagnosis and monitoring of various diseases. Pathological SAA values are often detected in association with normal CRP concentrations. SAA rises earlier and more sharply than CRP. Finally, contrary to CRP, SAA presents the same trend in viral as well as bacterial infections. Although the data available on SAA in neonates are currently very limited, it is possible to postulate a role of primary importance for SAA in the management of neonatal infections.

Serum amyloid A is a chemotactic agonist at FPR2, a low-affinity N-formylpeptide receptor on mouse neutrophils

Serum amyloid A (SAA) is an acute-phase plasma protein and the source of amyloid A, which accumulates in lesions of secondary amyloidosis. SAA can induce phagocyte migration in vitro and in vivo, and is a specific chemotactic agonist for the human low-affinity N-formylpeptide receptor FPRL1R, a G-protein-coupled receptor expressed on phagocytes. Here we show that FPR2, a mouse counterpart of FPRL1R, is also an SAA receptor. SAA selectively induced calcium flux and chemotaxis in mouse PMN, which express FPR2, as well as in HEK 293 cells expressing recombinant FPR2 but not in HEK 293 cells expressing FPR, a closely related high affinity N-formylpeptide receptor. Consistent with this, SAA activity on PMN from FPR+/+ and FPR-/- mice was indistinguishable. Moreover, the prototype N-formylpeptide fMLF desensitized SAA-induced calcium flux in a dose-dependent manner in both mouse neutrophils and HEK 293/FPR2 transfectants. Our results suggest that FPR2 specifically mediates mouse neutrophil migration in response to SAA.

Persistent Expression of Serum Amyloid A During Experimentally Induced Chronic Inflammatory Condition in Rabbit Involves Differential Activation of SAF, NF-κB, and C/EBP Transcription Factors

The serum amyloid A (SAA) protein has been implicated in the pathogenesis of several chronic inflammatory diseases. Its induction mechanism in response to a chronic inflammatory condition was investigated in rabbits following multiple s.c. injections of AgNO3 over a period of 35 days. During unremitting exposure to inflammatory stimulus, a persistently higher than normal level of SAA2 expression was seen in multiple tissues. Induction of SAA was correlated with higher levels of several transcription factor activities. Increased SAA-activating factor (SAF) activity was detected in the liver, lung, and brain tissues under both acute and chronic inflammatory conditions. In the heart, kidney, and skeletal muscle tissues, this activity remained virtually constant. In contrast, CCAAT enhancer binding protein (C/EBP) DNA-binding activity was transiently induced in selective tissues. Higher than normal NF-κB DNA-binding activity was detected in the lung and to a lesser extent in the liver and kidney tissues under both acute and chronic conditions. This result suggested that C/EBP, SAF, and NF-κB are required for transient acute phase induction of SAA whereas SAF and NF-κB activities are necessary for persistent SAA expression during chronic inflammatory conditions.

Serum amyloid A (SAA): a concise review of biology, assay methods and clinical usefulness

Serum amyloid A (SAA) is a family of proteins encoded in a multigene complex. Acute phase isotypes SAA1 and SAA2 are synthesized in response to inflammatory cytokines. SAA and C-reactive protein (CRP) are now the most sensitive indicators for assessing inflammatory activity. In viral infection and kidney allograft rejection, SAA proved more useful than CRP. Development of convenient assay methods for SAA will facilitate its use in clinical laboratories.

Activation of Sp1 and its functional co-operation with serum amyloid A-activating sequence binding factor in synoviocyte cells trigger synergistic action of interleukin-1 and interleukin-6 in serum amyloid A gene expression

The serum amyloid A (SAA) protein has been implicated in the progression and pathogenesis of rheumatoid arthritis through induction of collagenase activity in synovial fibroblast cells that line the joint tissues. We demonstrate that SAA is synergistically induced in synovial cells by interleukin (IL)-1 and IL-6 that are present at significantly high level in the synovial fluid of arthritis patients. These cytokines induced phenotypic changes in synovial cells, promoting protrusion and increased cellular contact. Induction of SAA under this condition is mediated by promoter elements located between -254 and -226, which contains binding sites for transcription factors Sp1 and SAA activating sequence binding factor (SAF). Mutation of these sequences abolishes SAA promoter response to IL-1 and IL-6. The role of Sp1 in SAA induction was demonstrated by increased DNA binding activity, phosphorylation, and increased protein content of Sp1 during cytokine treatment. Sp1 interacts with the SAA promoter in association with SAF as an SAF. Sp1 heteromeric complex. Furthermore, using a phosphatase inhibitor, we demonstrated increased transactivation potential of both Sp1 and SAF as a consequence of a phosphorylation event. These results provide first evidence for cytokine-mediated activation of Sp1 in synovial fibroblast cells and its participation in regulating SAA expression by acting in conjunction with SAF.

Isolation and functional characterization of cDNA of serum amyloid A-activating factor that binds to the serum amyloid A promoter

Serum amyloid A (SAA), a plasma protein inducible in response to many inflammatory conditions, is associated with the pathogenesis of several diseases including reactive amyloidosis, rheumatoid arthritis, and atherosclerosis. We have previously reported an element of the SAA promoter, designated SAA-activating sequence (SAS), that is involved in the inflammation-induced SAA expression, and a nuclear factor, SAS-binding factor (SAF), that interacts with the SAS element has been identified previously (A. Ray and B. K. Ray, Mol. Cell. Biol. 16:1584-1594, 1996). To evaluate how SAF is involved in SAA promoter activation, we have investigated structural features and functional characteristics of this transcription factor. Our studies indicate that SAF belongs to a family of transcription factors characterized by the presence of multiple zinc finger motifs of the Cys2-His2 type at the carboxyl end. Of the three cloned SAF cDNAs (SAF-1, SAF-5, and SAF-8), SAF-1 isoform showed a high degree of homology to MAZ/ZF87/Pur-1 protein while SAF-5 and SAF-8 isoforms are unique and are related to SAF-1/MAZ/ZF87/Pur-1 at the zinc finger domains but different elsewhere. Although structurally distinct, all members are capable of activating SAS element-mediated expression and display virtually identical sequence specificities. However, varying levels of expression of members of this gene family were observed in different tissues. Functional activity of SAF is regulated by a posttranslational event as SAF DNA-binding and transactivation abilities are increased by a protein phosphatase inhibitor, okadaic acid, and inhibited by a protein kinase inhibitor, H7. Consistent with this observation, increased DNA binding of the cloned SAF and its hyperphosphorylation, in response to okadaic acid treatment of the transfected cells, were observed. Taken together, our results suggest that, in addition to tissue-specific expression, SAFs, a family of zinc finger transcription factors, undergo a modification by a posttranslational event that confers their SAA promoter-binding activity and transactivation potential.

A novel cis-acting element is essential for cytokine-mediated transcriptional induction of the serum amyloid A gene in nonhepatic cells

Serum amyloid A (SAA) is a plasma protein which has been associated with several diseases, including amyloidosis, arthritis, and atherosclerosis, and its abnormal expression, particularly in nonhepatic cells, is implicated in the pathogenesis of these diseases. Transfection and DNA-binding studies were performed to investigate the mechanism controlling cytokine-induced, nonhepatic expression of the SAA gene. We have identified a novel promoter, located between positions -280 and 224, that confers interleukin-6 (IL-6) inducibility to an SAA-chloramphenicol acetyltransferase reporter gene in both nonhepatic and hepatic cells. DNase I protection assays revealed, within this region, three homologous highly pyrimidine rich octanucleotide sequence motifs, termed SAA-activating sequences (SAS). Specific mutations within these three SAS motifs severely reduced IL-6-mediated induction of the reporter gene in transfected nonhepatic cells but not in liver cells. A nuclear factor activated by IL-6 in both hepatic and nonhepatic cells efficiently interacts with the SAS. The induction kinetics and cycloheximide sensitivity of this SAS-binding factor (SAF) suggested that de novo synthesis of this factor itself or an activator protein is essential. Loss of DNA-binding ability as a result of in vitro dephosphorylation, induction of SAA-chloramphenicol acetyltransferase reporter gene activity in the presence of genistein, a protein kinase inhibitor, further indicate that a phosphorylation step is necessary for the activation of SAF. Our results suggest that SAF is a key regulator of cytokine-mediated SAA gene expression in some nonhepatic cells.

When does amyloidosis complicate systemic lupus erythematosus?

Secondary amyloidosis is a well recognised complication of rheumatic diseases, but the association with systemic lupus erythematosus is very unusual. We report the case of a patient with systemic lupus erythematosus who developed proteinuria due to renal amyloidosis. We also review the cases previously reported and the hypothesis on the pathogenic mechanisms.

Quantification and mapping of antigenic determinants of serum amyloid A (SAA) protein utilizing sequence-specific immunoglobulins and Eu3+ as a specific probe for time-resolved fluorometric immunoassay

Serum amyloid A (SAA) protein, the most prominent amongst acute-phase proteins, is the specific precursor protein of secondary reactive amyloidosis. The fact that SAA once released into the circulation as a 'free' protein rapidly associates with lipoproteins of the high-density range indicates a specific role in lipoprotein metabolism. In this study a new sensitive assay for quantification of human SAA protein in biological specimens using affinity-purified polyclonal antibodies and Eu3+ as a specific probe for time-resolved fluorometric immunoassay is presented. Both purified SAA and SAA-rich high-density lipoprotein particles served as reliable standards in the indirect and the direct sandwich dissociation-enhanced lanthanide fluorescence immunoassay (DELFIA). The detection limit of the DELFIA technique presented was 4-10 ng after sample dilution of 1/2500. The intra-assay coefficient of variation averaged 4.3% whereas the inter-assay coefficient of variation averaged 6.2%. Comparison with the nephelometric assay, a widely and commonly used assay for SAA quantification in plasma, revealed correlation coefficients of 0.9428. In addition to polyclonal anti-human SAA antibodies sequence-specific antibodies raised against synthetic peptides corresponding to region; 1-17, 14-30, 27-44, 40-63, 59-72, 68-84, 79-94, and 89-104 of the human SAA amino acid sequence were studied. Sequence-specific antibodies raised against epitopes 27-44, 59-72, 68-84, and 89-104 recognize human SAA protein in the DELFIA assay whereas antibodies raised against epitopes 1-17, 14-30, 40-63 and 79-94 failed to recognize the corresponding epitopes. Results obtained from these studies indicate that the N-terminal domain (1-30) as well as epitopes 40-63 and 79-94 of human SAA are apparently masked by the environment of the lipoprotein particle. From our studies it is proposed that the epitopes 31-39, 64-78, and 95-104 may be responsible for the interaction of SAA-rich high density lipoprotein particles with peripheral cells.

Serum amyloid A (SAA): an acute phase protein and apolipoprotein

Serum amyloid A (SAA) proteins comprise a family of apolipoproteins coded for by at least three genes with allelic variation and a high degree of homology between species. The synthesis of certain members of the family is greatly increased in inflammation. However, SAA is not often used as an acute-phase marker despite being at least as sensitive as C-reactive protein. SAA proteins can be considered as apolipoproteins since they associate with plasma lipoproteins mainly within the high density range, perhaps through amphipathic alpha-helical structure. It is not known why certain subjects expressing SAA develop secondary systemic amyloidosis. There is still no specific function attributed to SAA; however, a popular hypothesis suggests that SAA may modulate metabolism of high density lipoproteins (HDL). This may impede the protective function of HDL against the development of atherosclerosis. The potential significance of the association between SAA and lipoproteins needs further evaluation.

Serum amyloid A protein in acute viral infections

Concentrations of serum amyloid A protein (SAA) were measured in 254 children with viral diseases, including measles, varicella, rubella, mumps, echo-30 meningitis, chronic hepatitis B and C, and in eight with Kawasaki disease. Latex agglutination nephelometric immunoassay was used for assaying SAA. In 191 out of 195 patients (98%), SAA concentrations became markedly raised in the acute phase of the viral disease: measles (97%), varicella (100%), mumps (95%), and echo-30 meningitis (99%) with mean titres of 82.4, 80.5, 60.2, 75.2, and 101.1 micrograms/ml respectively. This increase in SAA was followed by a rapid return to normal concentrations (< 5 micrograms/ml) during convalescence. Remarkably higher concentrations of SAA (mean 1630 micrograms/ml) were detected in the acute phase of patients with Kawasaki disease, but in most of the children with chronic hepatitis B or C, the titres of SAA remained normal. There was no close correlation between SAA and serum concentrations for alpha 1-acid glycoprotein, beta 2-microglobulin, transferrin, and IgG. There was a clear correlation between SAA and C reactive protein concentrations, although SAA showed a greater incremental change than C reactive protein in the acute phase. In the acute phase of these viral diseases, 56% of the patients had raised SAA concentrations (> or = 5 micrograms/ml) with normal C reactive protein concentrations (< 5 micrograms/ml). These results indicate that SAA could be useful as an inflammatory marker in children with acute viral infections.

A rapid method for measuring serum amyloid A protein by latex agglutination nephelometric immunoassay

Serum amyloid A protein (SAA) is a sensitive acute phase reactant. We developed a method for the rapid measurement of human SAA in serum by kinetic nephelometry of anti-SAA antibody-coated latex agglutination. Measurement takes less than 6 min using an automated analyser. Standardization of the assay employs SAA-enriched high density lipoprotein as the primary standard. The values determined by our new method and by conventional enzyme-immunoassay showed good agreement (r = 0.988). The normal range was 0.17-10.0 mg/L [mean(SD)]. This rapid method should prove useful in clinical laboratories.

Alterations in lipoprotein density classes in infantile visceral leishmaniasis: presence of apolipoprotein SAA

This study describes the alterations in the plasma lipoproteins from nine young Tunisian children with active visceral Leishmaniasis. The plasma lipid profile from affected patients was characterized by a marked hypertriglyceridaemia associated with reduced levels of total and high density lipoprotein (HDL)-cholesterol and a significant increase in the plasma ratio of unesterified to total cholesterol. Quantitative determination of plasma apolipoproteins revealed significantly decreased levels of all measured apolipoproteins, especially of apolipoproteins A-I and A-II, with the exception of apolipoprotein E, the levels of which were markedly increased. Moreover, at least two isoforms of the apolipoprotein serum amyloid A (SAA), an acute phase protein, were detected in all patients' plasma using two-dimensional electrophoresis. Immunochemical evidence was presented that apolipoproteins E and SAA, although both primarily associated with apolipoprotein A- (A-I and A-II) as well as with apolipoprotein B-containing lipoproteins, could occur as LP-E and LP-SAA subspecies, devoid of apolipoproteins A and B. However, it should be pointed out that LP-SAA particles were found in HDL2 from only two patients whereas the abnormal LP-E particles were detected in LDL and HDL2 from all investigated patients. The polydispersity and heterogeneity of patients' HDL3 were assessed by electron microscopy. It was further suggested that the profound changes in the lipoprotein metabolism of these young patients may be due to the increased hepatic synthesis of apolipoprotein SAA and/or to their altered immune function during active visceral Leishmaniasis.

Comparison of serum amyloid A and C-reactive protein as indicators of lung inflammation in corticosteroid treated and non-corticosteroid treated cystic fibrosis patients

Serum amyloid A (SAA) and C-reactive protein (CRP) levels were compared in 830 serum samples from 155 cystic fibrosis (CF) patients. Correlation coefficients were calculated for all samples (r = 0.73), for samples from non-corticosteroid treated (CFNS) patients (n = 698, r = 0.80), and for samples from corticosteroid treated (CFS) patients (n = 132, r = 0.35). SAA was the more sensitive indicator of pulmonary inflammation when SAA and CRP were compared to pulmonary function tests of 49 hospitalized patients at admission and discharge. CRP levels were significantly (p less than .05) lower at admission in CFS patients than in CFNS patients, whereas SAA levels were not significantly different between the two groups. All nine CFS patients hospitalized had elevated SAA levels (average 22 times above normal limits) at admission, while only six had elevated CRP levels (average 3.7 times above normal limits) at admission. In the 40 CFNS patients both SAA and CRP levels were significantly elevated at admission. In each case SAA and CRP levels declined as pulmonary functions improved with effective antimicrobial therapy. In three instances SAA levels increased during hospitalization while CRP levels did not. In each case, rising SAA levels indicated clinical deterioration associated with evolving resistance of P. aeruginosa which required a change in antibiotic therapy.

A monoclonal antibody sandwich immunoassay for serum amyloid A (SAA) protein

An antibody sandwich immunoassay using two purified rat monoclonal antibodies to human serum amyloid A was developed and used to measure serum amyloid A in human serum. The assay was specific, sensitive, reproducible, and reliable and does not require denaturation of the specimen prior to assay. Serum amyloid A purified by hydrophobic interaction chromatography of acute phase human serum afforded a reliable standard for the assay. A significant (r = 0.69) correlation for SAA and C reactive protein values was found for 180 patient samples analyzed.

Serum amyloid A (SAA), a protein without a function: some suggestions with reference to cholesterol metabolism

Serum amyloid A, as an apolipoprotein, is present on high density lipoprotein only during inflammatory states. When viewed from HDL's established function as a mechanism for reverse cholesterol transportation, it is postulated that serum amyloid A represents a signal to redirect HDL to sites of tissue destruction where cholesterol is being collected by macrophages. The object is to direct the reverse cholesterol transporter to sites of cholesterol accumulation for the subsequent removal of these cholesterol stores. The hypothesis has relevance to the process of atheroma formation.

A sensitive immunochemiluminescence assay for human serum amyloid A protein

We describe an immunochemiluminescence assay for human plasma serum amyloid A protein (SAA) in which specific rabbit polyclonal antibodies against synthetic peptides are used. The detection of the antigen-antibody reaction at 425 nm is based on a brief emission of light by a luminophor component (signal) in response to chemical energy. The working range of the assay covers plasma SAA concentrations from 5 to 100 micrograms/L. The lower detection limit is 5 micrograms/L, the within- and between-assay CVs are less than 12%. Bilirubin, cholesterol and triglyceride in final concentrations of up to 220 mumol/L, 8.1 mmol/L and 2.68 mmol/L, respectively, do not interfere with the assay. Results were correlated with those obtained by the enzyme-linked immunosorbent assay using the same antibodies (r = 0.95; p less than 0.001; n = 50). This method is inexpensive, simple and easily automated.

Systemic AA amyloidosis induced by liver cell adenoma

Systemic AA amyloidosis is a rare complication of benign tumours. This report describes a patient with hepatocellular adenoma associated with reactive AA amyloidosis. He had a nephrotic syndrome with deteriorating renal function and an increase of serum concentrations of acute phase proteins, mainly C-reactive protein. Resection of the tumour was followed by improvement in renal function and a marked decrease of the serum concentrations of acute phase proteins.

Systemic amyloid associated with carcinoma of the bronchus

An association of systemic amyloid with a squamous cell carcinoma of the bronchus is described. Amyloid may be associated with myeloma and neuroendocrine tumours but has not been described in squamous cell carcinoma of the bronchus.

apo-SAA1/apo-SAA2 isotype ratios during casein- and amyloid-enhancing-factor-induced secondary amyloidosis in A/J and C57BL/6J mice mice

A/J mice are resistant while C57BL/6J are susceptible to casein-induced secondary amyloidosis. One mechanism responsible for this phenotypic expression of resistance/susceptibility was shown to operate at the level of production of the 'amyloid-enhancing factor' (AEF). AEF and processing of the apo-SAA protein appear almost concomitantly during amyloidogenesis. In order to determine if AEF played a role in the processing of the apo-SAA protein, three major parameters (apo-SAA1/apo-SAA2 ratios, level of AEF, and fibril formation) were determined during casein-induced secondary amyloidosis. Kinetics of AEF production and serum levels of the two major apo-SAA isotypes were compared in A/J and C57BL/6J animals. Both strains showed equal relative amounts of the two isotypes after seven, 15 and 21 casein injections, irrespective of the fact that the A/J strain had no detectable level of AEF and no amyloid deposition; while C57BL/6J mice had a high AEF level and were amyloidotic after 15 and 21 injections. An increased apo-SAA1/apo-SAA2 ratio due to a decrease in apo-SAA2 was noted after 38 days of casein injections when both strains had extensive deposits of amyloid fibrils. Involvement of AEF as an effector molecule was determined by following the ratio of the two major serum apo-SAA isotypes and fibril formation during an accelerated protocol of amyloid induction in C57BL/6J animals. AEF had no direct effect on apo-SAA isotype ratios in the serum.

Direct binding enzyme-linked immunosorbent assay (ELISA) for serum amyloid A (SAA)

A solid-phase, direct binding ELISA for serum amyloid A (SAA) proteins is described, in which noncovalent interactions of SAA with other plasma constituents are disrupted to permit direct coating of the wells of flexible polyvinyl chloride microtitration plates with an amount of SAA antigen proportional to its concentration in plasma. The wells are coated overnight at 60 degrees C with plasma diluted in 3 M potassium bromide and 0.1 M sodium bicarbonate. pH 9.6. The next day, any remaining sites on the wells are blocked by incubation for 1 h at ambient temperature with a 5% solution of dry milk solids and 0.05% Tween 20 in 0.02 M phosphate buffer, pH 7.4. The wells are rinsed and incubated for 90 min at 37 degrees C with polyclonal rabbit or rat anti-human SAA antiserum. Then, the wells are rinsed and incubated with goat anti-rabbit or rat IgG antiserum to which has been conjugated horseradish peroxidase. o-phenylenediamine and hydrogen peroxide substrates are added to the wells, color is allowed to develop, and sulfuric acid is added to stop the enzyme-catalyzed reaction. The amount of SAA coated to wells is quantified by absorbance at 490 nm. Four or more serial three-fold dilutions of plasma samples are assayed simultaneously on separate plates. Each plate contains a set of wells with identical concentrations of SAA standard protein diluted in decreasing concentrations of plasma proteins corresponding to the dilution of sample. The method can detect SAA concentrations in plasma samples ranging from 1 microgram/ml to greater than 1000 micrograms/ml. The method is suited to serial monitoring of SAA concentration in patients undergoing treatment for inflammatory conditions and to the quantitative analysis of large numbers of samples.

A rapid laser immunonephelometric assay for serum amyloid A (SAA) and its application to the diagnosis of kidney allograft rejection

We set up a laser nephelometric assay for the quantitation of serum amyloid A (SAA) in human plasma. Therefore monospecific antibodies were raised in sheep and used in parallel to measure SAA concentrations by nephelometry and also by radial immunodiffusion, an assay usually applied for determination of SAA. The nephelometric method is precise, simple and unlike radial immunodiffusion results are obtained within an hour. The antigen concentrations determined both by laser nephelometry and radial immunodiffusion correlated highly (r = 0.98). As plasma SAA concentrations were reported to be a possible marker of kidney allograft rejection, the assay was applied to measure SAA concentrations in patients after kidney transplantation. Data were compared with clinical and other biochemical parameters. The period after kidney transplantation is reported for two cases, where SAA plasma concentrations were helpful in diagnosing allograft rejection. The rapid availability of the SAA plasma concentrations by nephelometry makes them a possible additional tool to decide quickly upon antirejection therapy.

Quantitative dot-blot enzyme immunoassay for serum amyloid A protein

A dot-blot enzyme immunoassay is described which tests for serum amyloid A protein (SAA) using a commercially available antiserum. Heat treatment of the serum caused a marked increase in the apparent concentration of SAA. Pre-heated serum was directly bound to a nitrocellulose membrane using 'Bio-Dot' microfiltration apparatus to ensure uniformity. Then the SAA was stained using an 'Immun-Blot' assay kit (Bio-Rad, Laboratories, U.S.A.), and the optical density of the stained SAA spots was measured directly by a densitometer. The detection limit was 1.25 micrograms/ml of apoSAA1 (an isotype of SAA) dissolved in fetal bovine serum. The method had sufficient sensitivity to measure SAA in 76% of normal subjects. The method is ideally suited to the rapid processing of a large number of samples (up to 96 samples) using only a small amount of the antiserum.

The pathogenesis of reactive systemic amyloidosis

The diagnosis of amyloidosis is based on the presence of extracellular tissue deposits of proteinaceous material that demonstrate a characteristic green color when stained with Congo red and viewed under polarized light. Several different proteins are amyloidogenic but, in domestic animals, spontaneously occurring systemic amyloidosis is reactive in nature and characterized by the presence of amyloid protein AA. This type of systemic amyloidosis may occur secondary to chronic inflammatory or neoplastic disease, but in many instances no predisposing disease is found. A sustained increase in the serum concentration of serum amyloid A protein (SAA) is necessary but not sufficient for the development of reactive amyloidosis. Other inherited and acquired host-related factors are likely to be important in the development of reactive amyloidosis because this condition develops in few patients with chronic inflammatory disease. The tissue tropism of amyloid deposits varies with the amyloid protein itself and species affected. The consequences of amyloidosis for the host depend upon the tissues involved and the response of these tissues to the presence of the amyloid deposits. In domestic animals, reactive systemic amyloidosis is nephropathic, leading to end-stage renal disease, and the clinical presentation is that of uremia.

AA amyloidosis associated with systemic lupus erythematosus

A 54-year-old female with a 23-year history of systemic lupus erythematosus was admitted because of loss of renal function and nephrotic syndrome. Renal biopsy showed deposition of AA amyloid as demonstrated by Congo red staining and reactivity with protein AA-specific antibodies. Immune deposits were present in the mesangium and the glomerular basement membrane, but histopathological changes consistent with lupus nephritis were not detected. The rare association of systemic lupus erythematosus and amyloidosis is discussed in view of the characteristics of the acute phase reaction in systemic lupus erythematosus.