The role of IgM rheumatoid factor in experimental immune vasculitis. (49/235)

The effect of IgM rhematoid factor (RF) on reversepassive cutaneous Arthus reaction in rats was studied. The RF was obtained from the serum cryoglobulin of a patient with symptoms of purpura, arthralgia and digital gangrene. The cryoglobulins was of IgG-IgM type and when given i.v it induced a prompt hypocomplementaemia in experimental animals. The purified RF also induced low serum complement levels when injected i.v. along with complexes of non-complement-fixing, aggregated IgG. A reverse passive Arthus reaction was induced by intradermal injection of IgG anti-bovine serum albumin (BSA), followed by an i.v. dose of antigen (Ag). The cutaneous inflammatory reaction was aggravated by simultaneous administration of IgM RF intradermally, but not by IgM without antibody (Ab) properties. Intradermal injection of low concentrations of non-complement-fixing IgG anti-BSA, along with normal human IgM, followed by i.v. injection of BSA, resulted in a complete lack of cutaneous inflammation. At higher Ab concentrations there was only a mild inflammation. However, when IgM RF was substituted for normal IgM and injected with non-complement-fixing anti-BSA, an effective reverse passive cutaneous Arthus reaction and vasculitis was induced. The inflammatory response was greatly suppressed by decomplementation of animals by cobra venom factor. This study provides evidence favouring an inflammatory, complement-dependent role for RF in vasculitis.  (+info)

Characterization of cryoglobulins by immunoblotting. (50/235)

We adapted an immunoblotting technique for the immunochemical characterization of cryoglobulins. We first compared the results from 157 samples with results obtained by immunofixation and immunoelectrophoresis and then with clinical observations in 125 cases. Full identification was possible in 98% of the cases by immunoblotting, in 54% by immunofixation, and in 28% by immunoelectrophoresis. Novel microheterogeneity aspects were observed by immunoblotting and immunofixation in 13% and 6% of the cases studied, respectively. Our results confirm the frequency of autoimmune and infectious diseases associated with mixed cryoglobulinemias, whereas a lymphoproliferative syndrome was observed only in cases of cryoglobulinemia with a monoclonal constituent or a microheterogeneity aspect, which was not always revealed by immunofixation or immunoelectrophoresis. The pathophysiological importance and classification of microheterogeneity aspects is not clear. These observations justify using a sensitive and specific method for identifying cryoglobulins, even when present at low concentrations, and call for long-term studies of these patients.  (+info)

A critical role for sialylation in cryoglobulin activity of murine IgG3 monoclonal antibodies. (51/235)

Cryoprecipitating IgG3 autoantibodies have been shown to play a significant role in the development of murine lupus-like autoimmune syndrome. However, the structural basis of IgG3 cryoprecipitation still remains to be defined. In view of the implication of positively charged amino acid residues present in variable regions in IgG3 cryoglobulin activity, we explored the role of terminal sialic acids in oligosaccharide side chains for the cryogenic activity of IgG3 mAb. Comparative oligosaccharide structural analysis of different cryogenic and non-cryogenic IgG3 mAb showed an inverse correlation between the extent of sialylation and cryogenic activity. The inhibitory role of sialylation was further confirmed by the demonstration of enrichment of less and more sialylated IgG3 in cryoprecipitated and noncryoprecipitated fractions, respectively, separated from four different cryogenic IgG3 mAb. Significantly, the sialic acid contents of the latter fraction became comparable to those of non-cryogenic IgG3 mAb. Finally, we observed that highly sialylated non-cryogenic IgG3 mAb was more potent in the inhibition of cryoprecipitation of cryogenic IgG3 mAb. Our results thus suggest that the content of negatively charged sialic acids in oligosaccharide side chains is one of the critical factors to determine IgG3 cryoglobulin activity, along with amino acid sequences of the IgG3 variable regions.  (+info)

Crystal structure of a glycosylated Fab from an IgM cryoglobulin with properties of a natural proteolytic antibody. (52/235)

The 2.6 A (1 A=0.1 nm) resolution structure has been determined for the glycosylated Fab (fragment antigen binding) of an IgM (Yvo) obtained from a subject with Waldenstrom's macroglobulinaemia. Dynamic light scattering was used to estimate the gel point and monitor the formation of an ordered hydroscopic gel of Yvo IgM upon cooling. If a cryoglobulin forms gels in peripheral tissues and organs, the associated swelling and damage to microvasculature can result in considerable morbidity and mortality. The three-dimensional structure of the branched N-linked oligosaccharide associated with the CH1 domain (first constant domain of heavy chain) is reported. The carbohydrate may act to shield part of the lateral surface of the CH1 domain and crowd the junction between the CH1 and CH2 domains, thereby limiting the segmental flexibility of the Fab arms in intact Yvo IgM, especially at low temperatures. Recently, Yvo IgM was shown to have the properties of a naturally occurring proteolytic antibody [Paul, Karle, Planque, Taguchi, Salas, Nishiyama, Handy, Hunter, Edmundson and Hanson (2004) J. Biol. Chem. 279, 39611-39619; Planque, Bangale, Song, Karle, Taguchi, Poindexter, Bick, Edmundson, Nishiyama and Paul (2004) J. Biol Chem. 279, 14024-14032]. The Yvo protein displayed the ability to cleave, by a nucleophilic mechanism, the amide bonds of a variety of serine protease substrates and the gp120 coat protein of HIV. An atypical serine, arginine and glutamate motif is located in the middle of the Yvo antigen-binding site and displays an overall geometry that mimics the classical serine, histidine and aspartate catalytic triad of serine proteases. Our present findings indicate that pre-existing or natural antibodies can utilize at least one novel strategy for the cleavage of peptide bonds.  (+info)

Elevated plasma cryofibrinogen in patients with active inflammatory bowel disease is morbigenous. (53/235)

AIM: To investigate the role of cryofibrinogen (CF) in active inflammatory bowel disease (IBD). METHODS: CF was assayed in 284 subjects: 61 with active and 63 with inactive ulcerative colitis (UC), 45 who had proctocolectomy, 35 with active and 20 with inactive Crohn's disease (CD), 40 with other diseases and 20 healthy controls. Trypsin inhibitor (TI) and TI antibody (TI-Ab) were measured in plasma and CF complex by ELISA. RESULTS: CF in active UC was strikingly high compared with all other groups (c2<0.001). Similarly, CF was significantly higher in active CD than in inactive CD or in controls (c2<0.01). In UC, high CF and TI-Ab were associated with the need for operations. Further, high CF, CF/fibrinogen ratio, low TI and high TI-Ab in plasma were associated with disease activity or refractoriness to medication. Elevated CF was not associated with acute reactants like C-reactive protein and white blood cell counts except for erythrocyte sedimentation rate, suggesting that elevated CF was not a consequence of acute inflammation. CONCLUSION: Elevated CF in active IBD appears to be morbigenous. CF promotes IBD via two main mechanisms, quenching of TI (an anti-inflammatory substance) and impairing microvascular perfusion by forming protein aggregates. CF may also serve as a biomarker of chronic IBD. Additional studies are warranted to fully evaluate the role of CF in IBD and the outcome should contribute to a better understanding of the pathogenesis of IBD.  (+info)

Factors determining successful liver preservation for transplantation. (54/235)

Auxiliary liver allotransplants will survive for relatively long periods of time after 24 hour hypothermic (10-12C), pulsatile perfusion. The best perfusate was a silica gel fraction of dog plasma with added potassium chloride gel made hyperosmolar with glucose. Further improvement could be achieved with added allopurinol and methylprednisolone. Nonpulsatile flow or lower temperatures were less effective preservation techniques.  (+info)

Cryoimmunoglobulinemia in rheumatoid arthritis. Significance in serum of patients with rheumatoid vasculitis. (55/235)

Cryogloculins were examined in a standardized manner in an unselected group of 35 patients with rheumatoid arthritis (RA) and 8 patients with RA complicated by cutaneous vasuclitis and neuropathy. Optimum conditions for detection and characterization of cryoglobulins were established; the proportion of resolubilized to total precipitable protein remained constant in an individual patient under these conditions. All 8 vascultis patients and 9 of 35 other patients with RA exhibited cryoglobulins; total protein and immunoglobin content were significantly higher in the cryoglobulins of patients with vasculitis. Immunoglobulins G and M constituted two-thirds and three-quarters of the total protein in the cryoglobulins from uncomplicated rheumatoid and vasculitis patients, respectively. Serum antiglobulin titers were higher, and serum C3 levels were lower, in vasculitis patients compared to rheumatoid patients without vasclitis. Anti-gamma globulin activity was detected in all cryoglobulins from vasculitis patients. Cryoglobulin IgG and IgM were polyclonal. Density gradient analyses demonstrated the majority of the cryoglobulin activity to reside in the 19S IgM fraction. There was no evidence of a light weight (8S) IgM. A monoclonal rheumatoid factor did not detect 7S-ANTI-7S complexes in the cryoprecipitates, but acid eluates from some cryoglobulins absorbed with insoluble IgG revealed an antiglobulin of the IgG class. Serial studies performed on vasculitis patients treated with cyclophosphamide disclosed a relationship between clinical evidence of vasculitis and the presence of cryoglobulins. The antigen (IgG) and antibody (largely IgM rheumatoid factor) nature of these cryglobulins is presented as evidence that the widespread vascular complications of RA are mediated, at least in part, by circulating immune complexes.  (+info)

Quantitative measurement of hepatitis C virus core antigen is affected by the presence of cryoglobulins. (56/235)

Mixed cryoglobulinaemia is associated strikingly with HCV infection. The aim of this study was to assess whether the adherence to proper methods of collecting samples for cryoglobulin detection was critical or not on virological parameters in hepatitis C virus (HCV) patients. We studied 56 consecutive patients. Blood samples were collected using a conventional method and a blood collection method at 37 degrees C adapted to cryoglobulin detection. HCV core antigen and HCV RNA were measured in sera and cryoglobulins issued from both blood collection methods. In cryoglobulin-positive patients, serum concentrations of HCV core antigen, but not that of HCV RNA, were significantly higher when a conventional method was used, compared to a blood collection method at 37 degrees C (P = 0.001). In the cryoprecipitates, concentration of HCV core antigen was optimum when the blood collection method at 37 degrees C, rather than the conventional method, was applied for cryoglobulin detection (P < 10(-4)). The recovery of HCV core antigen in the cryoprecipitate was improved when cryoglobulins were isolated using the blood collection method at 37 degrees C rather than the conventional method (P < 0.001). HCV parameter measurements and cryoglobulin study should not be performed on the same serum samples due to the potential impact of blood collection methods on results.  (+info)