Rheumatoid Factor Activity Research Articles

Cryoglobulinemia

Cryoglobulinemia refers to the presence in serum of immunoglobulins that precipitate at a cold temperature. Type I cryoglobulins are single monoclonal immunoglobulins usually associated with haematological disorders. Types II and III are mixed cryoglobulins, composed of monoclonal or polyclonal IgM respectively, having rheumatoid factor activity that bind to polyclonal immunoglobulins. Mixed cryoglobulinemia (MC) syndrome is a consequence of immune-complex mediated vasculitis and is characterized by a typical clinical triad: purpura, weakness, arthralgias; many organs particularly kidney and peripheral nervous system may be involved. MC may be associated with infectious and systemic disorders and since 1990 studies have demonstrated that hepatitis C virus (HCV) may be considered the principal trigger of the disease. The relation between MC and HCV infection shows new insights in the interpretation of the link between viral infection, autoimmune phenomena and lymphoproliferative disorders evolution. In fact, the virus chronically stimulates B-cell polyclonal proliferation from which a monoclonal population may emerge. In symptomatic patients with HCV related MC therapeutic strategy should include an attempt at viral eradication. Antiviral therapy may also be effective in determining the regression of B-cell lymphoproliferative disorder. Rituximab could represent a safe and effective alternative to standard immunosuppression and exerts selective B-cell control.

The Role of Complement in Cryoglobulin-Induced Immune Complex Glomerulonephritis

Many forms of glomerulonephritis are triggered by Ab localization in the glomerulus, but the mechanisms by which this induces glomerular inflammation are not fully understood. In this study we investigated the role of complement in a mouse model of cryoglobulin-induced immune complex glomerulonephritis. Several complement-deficient mice on a C57BL/6 and BALB/c genetic background were used and compared with strain-matched, wild-type controls. Cryoglobulinemia was induced by i.p. injection of 6-19 hybridoma cells producing an IgG3 cryoglobulin with rheumatoid factor activity against IgG2a of allotype a present in BALB/c, but not C57BL/6, mice. Thus, the cryoprecipitate in C57BL/6 mice consisted of the IgG3 cryoglobulin only (type I cryoglobulinemia) compared with IgG3-IgG2a complexes in BALB/c (type II cryoglobulinemia). The survival of mice was not affected by complement deficiency. Glomerular influx of neutrophils was significantly less in C3-, factor B-, and C5-deficient mice compared with wild-type and C1q-deficient mice. It did not correlate with C3 deposition, but did correlate with the amount of C6 deposited. Deficiency of CD59a, the membrane inhibitor of the membrane attack complex, did not induce an increase in neutrophil infiltration, suggesting that the generation of C5a accounts for the effects observed. There was no apparent difference between cryoglobulinemia types I and II regarding the role of complement. Our results suggest that in this model of cryoglobulin-induced glomerulonephritis the neutrophil influx was mediated by C5 activation with the alternative pathway playing a prominent role in its cleavage. Thus, blocking C5 is a potential therapeutic strategy for preventing renal injury in cryoglobulinemia.

Early rheumatoid arthritis is characterized by a distinct and transient synovial fluid cytokine profile of T cell and stromal cell origin

Pathological processes involved in the initiation of rheumatoid synovitis remain unclear. We undertook the present study to identify immune and stromal processes that are present soon after the clinical onset of rheumatoid arthritis (RA) by assessing a panel of T cell, macrophage, and stromal cell related cytokines and chemokines in the synovial fluid of patients with early synovitis. Synovial fluid was aspirated from inflamed joints of patients with inflammatory arthritis of duration 3 months or less, whose outcomes were subsequently determined by follow up. For comparison, synovial fluid was aspirated from patients with acute crystal arthritis, established RA and osteoarthritis. Rheumatoid factor activity was blocked in the synovial fluid samples, and a panel of 23 cytokines and chemokines measured using a multiplex based system. Patients with early inflammatory arthritis who subsequently developed RA had a distinct but transient synovial fluid cytokine profile. The levels of a range of T cell, macrophage and stromal cell related cytokines (e.g. IL-2, IL-4, IL-13, IL-17, IL-15, basic fibroblast growth factor and epidermal growth factor) were significantly elevated in these patients within 3 months after symptom onset, as compared with early arthritis patients who did not develop RA. In addition, this profile was no longer present in established RA. In contrast, patients with non-rheumatoid persistent synovitis exhibited elevated levels of interferon-γ at initiation. Early synovitis destined to develop into RA is thus characterized by a distinct and transient synovial fluid cytokine profile. The cytokines present in the early rheumatoid lesion suggest that this response is likely to influence the microenvironment required for persistent RA.

Cold Agglutinin Disease and Cryoglobulinemia

Cold agglutinin disease is a form of direct, extravascular, antiglobulin-positive hemolysis. In vivo, immunoglobulin (Ig) M fixes complement molecules to the red cell membrane. Successive passages through the mononuclear phagocyte system result in loss of red cell membrane. The resultant spherocytes lose resiliency and are ultimately lost from the circulation extravascularly. The high concentration of complement molecules on the red cell surfaces makes this syndrome resistant to the standard therapies for immune-mediated hemolysis. Rituximab has been reported to reduce the severity of hemolysis. Type II cryoglobulins are composed of a monoclonal IgM and a polyclonal IgG. These complexes have rheumatoid factor activity and can produce immune-complex vasculitis. The target organs are the skin, nerves, kidney, liver, and joints. More than 80% of patients have evidence of hepatitis C infection. Interferon and interferon plus ribavirin have been shown to produce serologic responses. When vasculitis is active, corticosteroids are often required to permit healing of ulcers in the skin or to treat the membranoproliferative glomerulonephritis that is seen, thereby preventing loss of renal function. Rituximab therapy has been found to be effective in mixed cryoglobulinemia, with decreases in cryoglobulin values and improvement in complement values.

A longitudinal study of the relationship between galactosylation degree of IgG and rheumatoid factor titer and avidity during long-term immunization of rabbits with BSA

Although IgG with reduced content of galactose has been implicated as important in the autoimmune rheumatoid factor (RF) response in rheumatoid arthritis (RA), relatively little is known about the temporal relationship between RF and the degree of galactosylation of IgG in vivo. We established an experimental model for studying the dynamic association between changes in the relative extent of galactosylation of IgG antigen(s) and the main parameters of RF activity, such as the titer, specificity and functional affinity/avidity. Rabbits hyperimmunized with BSA were used for examining the influence of long-term antigenic stimulation on the galactosylation status of IgG and rheumatoid factor production. The results showed that the galactosylation profile of IgG varied during the humoral anti-BSA response in rabbits and that the accompanying RF response fluctuated in titer and binding avidity for differently galactosylated IgG. The immune complexes (IC) were found to be composed of differently galactosylated IgG differing in capacity to inhibit the agglutination activity of RF. Moreover, the ability of circulating RF to react avidly with rather small IC was associated with a lower content of galactose in complexed IgG. The results suggest that a certain dynamic relationship exists between the oligosaccharide moiety of IgG and the titer and avidity of RF during the normal anti-BSA response of rabbits.

Comparison of CpG s-ODNs, chromatin immune complexes, and dsDNA fragment immune complexes in the TLR9-dependent activation of rheumatoid factor B cells

Synthetic single-stranded oligodeoxynucleotides (15—30 bp) containing CpG motifs and phosphorothioate backbones (CpG s-ODN), immune complexes consisting of anti-nucleosome mAbs and mammalian chromatin (chromatin IC), and immune complexes consisting of anti-hapten mAbs and haptenated-double stranded DNA fragments (~600 bp) can all effectively stimulate transgenic B cells expressing a rheumatoid factor receptor by a TLR9-dependent process. However, differential sensitivity to both s-ODN and small molecule inhibitors suggests that stimulatory CpG sODN and chromatin IC may either access TLR9 via different routes or depend on discrete activation parameters. These data have important implications regarding the therapeutic application of TLR9 inhibitors to the treatment of systemic autoimmune diseases.

Non-enveloped HCV core protein as constitutive antigen of cold-precipitable immune complexes in type II mixed cryoglobulinaemia.

Hepatitis C virus (HCV) infection has been detected in a large proportion of patients with mixed cryoglobulinaemia (MC). Circulating 'free' non-enveloped HCV core protein has been demonstrated in HCV-infected patients, and this suggests its possible involvement in the formation of cryoprecipitable immune complexes (ICs). Thirty-two anti-HCV, HCV RNA-positive patients with type II MC were evaluated. Non-enveloped HCV core protein, HCV RNA sequences, total IgM, rheumatoid factor (RF) activity, IgG and IgG subclasses, C3 and C4 fractions, C1q protein and C1q binding activity were assessed in both cryoprecipitates and supernatants. Non-enveloped HCV core protein was demonstrated in 30 of 32 (93.7%) type II MC patients. After separation of cold-precipitable material, the protein was removed completely from supernatant in 12 patients (40%), whereas it was enriched in the cryoprecipitates of the remaining 18. In addition, HCV RNA and IgM molecules with RF activity were concentrated selectively in the cryoprecipitates. Differential precipitation was found for both total IgG and IgG subclasses, as they were less represented in the cryoglobulins and no selective enrichment was noted. Immunological characterization of HCV core protein-containing cryoprecipitating ICs after chromatographic fractionation showed that the IgM monoclonal component had RF activity, whereas anti-HCV core reactivity was confined to the IgG fraction. C1q enrichment in addition to high avidity of ICs for C1q binding in the cryoprecipitates suggest that complement activation may occur through the C1q protein pathway. The present data demonstrate that non-enveloped HCV core protein is a constitutive component of cryoprecipitable ICs in type II MC patients.

Hepatitis C virus–related cryoglobulinemic glomerulonephritis: Long-term remission after antiviral therapy

Renal involvement in patients with hepatitis C virus (HCV) infection commonly manifests as cryoglobulinemic glomerulonephritis (CGN). The combination of interferon-alpha (IFN-alpha) and ribavirin, which is currently considered the standard antiviral therapy in chronic hepatitis C, could be difficult to carry out in cryoglobulinemic patients who are frequently anemic, even in the absence of renal failure. Clinical and histologic long-term results of this therapeutic regimen have not been so far reported in patients with CGN. Three patients with HCV-related CGN and slightly impaired kidney function were treated with IFN-alpha and ribavirin for 12 months, and subsequently were followed up for 24 to 36 months. Two of these patients who were anemic were pretreated with erythropoietin (EPO). In each patient renal biopsy was performed before starting therapy and repeated 14 to 26 months after the end of treatment. In all three patients, antiviral therapy induced sustained virologic response, which was followed by clear improvement in clinical, biochemical, immunologic, and histologic features. Clinical and biochemical improvement steadily progressed in all three patients, achieving normal or nearly normal results at the end of follow-up. In contrast, some immunologic features, such as serum levels of C4 and rheumatoid factor activity, did not normalize in two and three patients, respectively. Posttreatment renal biopsies showed mildly active histologic lesions. Antiviral therapy with IFN-alpha and ribavirin may be considerably beneficial in patients with HCV-related CGN who obtain sustained virologic response.

Monoclonal antibody treatment of mixed cryoglobulinemia resistant to interferon α with an anti-CD20

AbstractA controlled study has been carried out to assess the efficacy of rituximab, a chimeric antibody that binds to the B-cell surface antigen CD20, in 20 patients with mixed cryoglobulinemia (MC) and hepatitis C virus (HCV)–positive chronic active liver disease, resistant to interferon α (IFN-α) therapy. They received an intravenous infusion of 375 mg/m2 rituximab once a week for 4 consecutive weeks. Infusion of rituximab had a good safety profile and no severe side effects were reported. Sixteen patients (80%) showed a complete response (CR), characterized by rapid improvement of clinical signs (disappearance of purpura and weakness arthralgia and improvement of peripheral neuropathy), and decline of cryocrit. CR was associated with a significant reduction of rheumatoid factor (RF) activity and anti-HCV antibody titers. Decline of IgG anti-HCV titers in the cryoprecipitates was usually associated with a favorable response (r = 0.81; P < .005). No differences in the dynamics of B-cell depletion and recovery were found between responders and nonresponders. Molecular monitoring of the B-cell response revealed disappearance/deletion of peripheral clones in the responders and great stability in the nonresponders. Rituximab had a deep impact on hepatitis C viremia; HCV RNA increased approximately twice the baseline levels in the responders, whereas it remained much the same in the nonresponders. Twelve (75%) of 16 responders remained in remission throughout the follow-up. The results indicate that rituximab has clinical and biologic activity in patients with HCV+ MC. However, in view of the increased viremia in the responders, additional modes of application and combination of rituximab with other agents need to be investigated.

Activation of rheumatoid factor (RF) B cells and somatic hypermutation outside of germinal centers in autoimmune-prone MRL/lpr mice.

Two critical questions need to be answered concerning the origins of autoreactive B cells in autoimmunity. First, how are autoreactive B cells regulated in normal situations? Second, how do such B cells escape tolerance mechanisms during autoimmunity? To address these questions, an Ig transgenic (Tg) mouse system based on the rheumatoid factor (RF) specificity has been developed. Tg mice express either the H or both H and L chains from AM14, an MRL/lpr-derived RF. Using this system, it was first shown that RF B cells are neither tolerized nor activated in a normal mouse. New insights into the timing and sites of initial RF B cell activation in MRL/lpr mice have been gained recently. RF B cells are activated. It was found, unexpectedly, that RF B cell activation, somatic hypermutation, and selection take place outside of the germinal center. We discuss the implications of this for the regulation of autoreactive B cells as well as for the regulation of hypermutation.

Hepatitis-C-virus-associated cryoglobulinemia. Pathogenesis, diagnosis and treatment

Chronic hepatitis C-virus (HCV) infection is frequently associated with a variety of autoimmune phenomenons. Mixed cryoglobulins appear in up to 50% of chronic HCV-infected patients, mostly asymptomatic. Cryoprecipitates present IgM with rheumatoid factor activity and development of immunocomplexes deposited in small vessels responsible for resulting vasculitis. MANIFESTATIONS: Characteristic clinical findings are weakness, arthralgia and purpura with further complications including glomerulonephritis and neuropathic lesions. Several mechanisms for HCV-induced clinical lymphoproliferation are discussed, such as chronic B-cell stimulation and activation of the antiapoptotic oncogene bcl-2 leading to immunoglobulin synthesis and eventually evolving into B-cell non-Hodgkin's lymphoma (NHL). Conventional treatment of HCV-associated mixed cryoglobulinemia aimes at reducing circulating immunocomplexes and causal therapy with interferon (IFN) and ribavirin. New approaches using the anti-CD20 antibody rituximab have been described recently.

Interference by rheumatoid factor activity in the detection of antiavian antibodies in pigeon breeders disease.

The assessment of antiavian antibodies is relevant for the study of pigeon breeder's disease; nevertheless, different factors may hamper their accurate detection. The objective of this study was to determine whether an endogenous interfering effect in pigeon breeder's disease might explain the simultaneous presence of IgM, IgG, and IgA antiavian antibodies in high titers as assessed by ELISA. Fifty-nine patients with pigeon breeder's disease, 80 healthy controls, and 47 asymptomatic breeders were studied. To assess possible interfering effects by endogenous immunoglobulins, serum IgG was separated through protein A-Sepharose CL-4B chromatography. Antiavian antibodies were measured in whole and separated samples by ELISA. Since a decline of IgM antiavian antibodies following IgG removal was consistent with a false-positive effect, the causes were studied. High values of IgM, IgG, and IgA antiavian antibodies were found in 47.4% [corrected] of patients with pigeon breeder's disease. An IgM rheumatoid factor activity against IgG was found through ELISA in sera with false-positive IgM antiavian antibodies. Rheumatoid factor binding was confirmed by Western blot. Experimental addition of purified rheumatoid factor to sera with IgG antiavian antibodies replicated the interfering effect. A control group of rheumatoid arthritis with high rheumatoid factor values did not show positive antiavian antibodies tests. No IgG with anti-IgM or anti-IgA activity was found, and the detection of IgA against IgM and IgG was negative. In conclusion, the study of antiavian antibodies might be affected by different immunoassay conditions. An endogenous rheumatoid factor activity produced false-positive IgM results. Other similar interferences warrant a careful evaluation during the serological assessment of pigeon breeder's disease.

Chromatin-IgG complexes activate B cells by dual engagement of IgM and Toll-like receptors.

Autoreactive B cells are present in the lymphoid tissues of healthy individuals, but typically remain quiescent. When this homeostasis is perturbed, the formation of self-reactive antibodies can have serious pathological consequences. B cells expressing an antigen receptor specific for self-immunoglobulin-gamma (IgG) make a class of autoantibodies known as rheumatoid factor (RF). Here we show that effective activation of RF+ B cells is mediated by IgG2a-chromatin immune complexes and requires the synergistic engagement of the antigen receptor and a member of the MyD88-dependent Toll-like receptor (TLR) family. Inhibitor studies implicate TLR9. These data establish a critical link between the innate and adaptive immune systems in the development of systemic autoimmune disease and explain the preponderance of autoantibodies reactive with nucleic acid-protein particles. The unique features of this dual-engagement pathway should facilitate the development of therapies that specifically target autoreactive B cells.

Recognition of IgG-derived peptides by a human IgM with an unusual combining site.

A monoclonal immunoglobulin (Ig)M cryoglobulin (Mez) with interesting binding behaviour was isolated from a Waldenström's macroglobulinemia (WM) patient. It demonstrated very strong binding to peptides derived from the sequences of human IgG. However, when tested for binding to intact IgG, this antibody (Ab) did not show any rheumatoid factor (RF) activity. We propose several nonexclusive structural interpretations of the Mez-binding propensities, based on the orientations and solvent accessibilities of ligand residues and the nature of the Ab-binding site. To further characterize the structural features of Mez-peptide binding, IgG-derived octapeptides were docked into the Mez fragment variable (Fv)-binding site, revealing additional reasons for Mez-binding selectivity based on the interactions of the docked peptides with the Mez Fv. The problem was also approached from an immunological perspective. Comparisons of Mez variable region of the light chain (VL)/variable region of the heavy chain (VH) sequences with those of human germlines and known IgM RFs allowed us to provide a possible outline tracing the structural and functional origins of the Mez IgM. Coupled with examinations of interactions in docked complexes, this analysis led us to propose that the potential for RF activity, demonstrated through Mez binding to IgG-derived peptides, was owing to the inherent sequence and structure of the Mez IgM, rather than to somatic mutations. Thus, Mez IgM may occupy an intermediate niche between IgMs with and without RF activity.

Characterization of Anti-Phosphatidylcholine Polyreactive Natural Autoantibodies from Normal Human Subjects

In 1990 our group reported a patient with autoimmune hemolytic anemia and high titers of IgM anticardiolipin antibodies that cross-reacted with phosphatidylcholine (PTC). These autoantibodies also recognized bromelain-treated erythrocytes (BrE) and in vitro aged erythrocytes. The epitope exposed with this treatment is PTC. To detect and characterize antiphosphatidylcholine antibodies (anti-PTC) in a normal human population, we studied by ELISA the presence of serum anti-PTC (IgG and IgM) in clinically healthy human subjects. The most representative samples were also studied for IgG or IgM activity against BrE by flow cytometry, rheumatoid factor activity, anti-dsDNA, anti-ssDNA by ELISA and by indirect immunofluorecence (IIF) using HEp-2 line and a healthy human fibroblast strain as substratum. Eighty five percent of sera had IgM anti-PTC and none had IgG. IgM antibodies against BrE were inhibited by PTC micelles (mPTC). Anti-PTC were also inhibited by phosphorylcholine and phosphatidic acid. Aggregated gammaglobulin (AGG) reactivity was inhibited by dsDNA and mPTC. The IgM anti-dsDNA activity was inhibited by soluble dsDNA, AGG and mPTC. All sera gave intermediate filaments pattern by IIF and reacted against purified vimentin by dot blot and Western blot.Our study shows hemolytic IgM anti-PTC present in normal human serum. The main epitope recognized by these autoantibodies is phosphorylcholine. The physicochemical characteristics, crossreactivity with self-antigens and functional properties are typical features of natural autoantibodies.

Hepatitis C Virus, B-cell Proliferation and Lymphomas

Accumulating evidence support a role for hepatitis C virus (HCV) in the pathogenesis of human lymphoproliferative disorders. Clonal expansions of B lymphocytes have been prevalently detected in the bone marrow, in the liver and in the peripheral blood of HCV-infected patients. Epidemiologic studies have associated HCV infection with an increased risk of B-cell lymphoma development, particularly of those with primary localization to organs target of HCV infection. The analysis of the B-cell receptor variable region sequences in sequential phases of HCV-associated lymphomas provided evidence of an ongoing somatic mutation process still present in the neoplastic cells. A restricted repertoire of V, D, J genes was used to assemble the B-cell receptor, and a frequent occurrence of certain gene combinations (V1-69/D3-22/J4 heavy chain with a V3-20 encoded light chain; V3-7/D3/J3 heavy chain with V3-15/J1 light chain; V3-23/D3-22/J4 or V4-59/D2-15/J2 with a V3-20 light chain) was observed, thus suggesting a common antigen-binding specificity for these B-cell clones. The high similarity to antibodies with rheumatoid factor (RF) activity as well as to anti-HCV E2 antibodies suggested that HCV, alone or in complex with IgG, could play a pathogenetic role as an exogenous trigger in certain stages of B-cell lymphoproliferation and in certain subsets of B-cell non-Hodgkin's lymphomas (NHLs). The restricted gene repertoire used to assemble the B-cell receptor observed in HCV-associated B-cell NHLs could have important implications as an antigenic target in anti-tumor immunologic therapies.

High incidence of extrahepatic manifestations in an HCV hyperendemic area

We previously investigated the incidence of extrahepatic manifestations including oral precancerous disease among the inhabitants in a hepatitis C virus (HCV) hyperendemic area in Fukuoka in Japan. The present study design was based on a prospective cohort at the other HCV hyperendemic area. One oral surgeon examined the oral lesions of 59 adult inhabitants (21 men, 38 women; mean age of 70.7 years), of a hyperendemic area of HCV infection. Furthermore, all subjects were interviewed regarding the natural history of extrahepatic manifestations. All sera were examined for antibodies to HCV (anti-HCV), serum HCV RNA, HCV genotype, antinuclear antibody (ANA), rheumatoid factor (RF) activity, and anti-SS-A and-B antibodies. Anti-HCV or HCV RNA was detected in sera from 59 (100%) or 57 (96.7%) of all subjects. Oral lichen planus (OLP), leukoplakia with leukoedema, or only leukoedema was observed in 8 (8.5%), 1 (1.7%), or 2 (3.4%) subjects, respectively. The incidence of all subjects with one or more HCV-related extrahepatic manifestation was 66.1% (39/59). The subjects with dry mouth were 25.4% (15/59). There was no relation among these autoantibodies, symptoms of dry mouth, or prevalence of HCV-associated extrahepatic manifestations. These findings demonstrate that the inhabitants with HCV infection showed various extrahepatic manifestations, and was not always limited to specific HCV areas.

Hepatitis C virus-associated mixed cryoglobulinemia. Clinical manifestations, histopathological changes, mechanisms of cryoprecipitation and options of treatment.

Chronic hepatitis C virus (HCV) infection is frequently associated with a variety of autoimmune phenomenons. Mixed cryoglobulinemia (MC) appears in up to 50% of chronic HCV-infected patients. Cryoglobulins consist of immunoglobulin complexes precipitating in vitro when cooled below body temperature. In most cases IgM with rheumatoid factor activity is found in cryoprecipitates which could lead to vasculitis induced by the deposition of immnuocomplexes in small vessels. This vasculitis is thought to cause clinical symptoms called Meltzer's triad. This triad is represented by purpura, arthralgia and weakness. One third of patients suffering from HCV-associated mixed cryoglobulinemia are developing typical symptoms during their course of disease. The striking association between HCV infection and MC has conduced to the hypothesis that HCV is of major importance in the production of MC with followed vasculitis. Both hepatrophism and lymphotrophism have been reported for the hepatitis C virus. Infection of B-cells by HCV could probably lead to a bcl-2 translocation and immunoglobulin gene rearrangement which results in clonal lymphoproliferation and in synthesis of monoclonal IgM with rheumatoid factor activity. These IgM form immunocomplexes with IgG in the cold, which are finally responsible for the described vasculitis. Histopathological changes of the liver are dominated by chronic HCV infection. The majority of times mild activity of hepatitis or mild fibrosis could be found. Nevertheless, cirrhosis is more often found in HCV-infected patients suffering from MC compared to patients without MC. Conventional treatment of MC is aimed to reduce circulating immune complexes by immunosupression and plasmapheresis. With the emerging concept of a viral pathogenesis the therapeutic approach has changed during the last decade. Interferon treatment of MC, particularly of HCV-associated MC is well established nowadays.

The cryoglobulins: an overview.

Cryoglobulins are cold-precipitable immunoglobulins associated with a number of infectious, autoimmune and neoplastic disorders. Their appearance along with rheumatoid factor (RF) can be considered a normal event in the clearance of immune complexes and rarely produces any symptoms. The association between hepatitis C virus (HCV) and mixed cryoglobulinemia (MC) has been rendered evident since the recognition of serological markers of HCV infection. There is thus every reason to suppose that direct or indirect involvement of B cells on the part of the HCV results in their persistent stimulation, clonal expansion and release of molecules with RF activity. The formation of RF/IgG immune complexes is the key pathogenetic mechanism. The close correlation between HCV infection and MC also throws new light on the interpretation of autoimmune phenomena in the course of viral infection and on the close link between autoimmune diseases and lymphoproliferative disorders. The higher risk of non-Hodgkin's lymphoma (NHL) displayed by HCV positive subjects, especially in the Mediterranean basin, suggests that the HCV's chronic lymphoproliferative drive may progress towards frank lymphoid neoplasia. The presence of MC does not represent an in situ or 'occult' NHL, because recent evidences indicate that none of the clones interpreted as predominant displays the molecular features of a true neoplastic process. The cryoglobulinemic syndrome is probably the consequence of pathogenic noxae that act upon the immune system of a host in which regulation of the peripheral T cell response appears to be in some way altered.

A case of fulminant mixed cryoglobulinemia developing after atrial myxoma resection.

A 63-year-old man, with a 13-year history of asymptomatic proteinuria, was diagnosed with left atrial myxoma at the onset of heart failure. After resection of the tumor by hypothermal surgery, the patient developed fever, renal failure and skin rash. The diagnosis was type II mixed cryoglobulinemia accompanied by an IgMlambda clone with high titers of rheumatoid factor activity and polyclonal IgG. Treatment with high doses of steroids and plasmapheresis was ineffective, and the patient died of colon necrosis due to thrombotic occlusion in the supra-mesenteric arteries. Although the patient had suffered from sporadic Raynaud's phenomenon and purpura of the lower extremities from the age of 60 years, cryoglobulinemia was not suspected before surgery because of the atrial myxoma. Thus, we suggest that it is important to perform laboratory tests for cryoproteins before hypothermal surgery.