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.

Human monoclonal gamma G-cryoglobulins with anti-gamma-globulin activity

Seven human gammaG-myeloma proteins which were also cryoglobulins were studied with respect to their reactivity with gammaG-globulins as well as with regard to their antigenic classification within the gammaG-heavy chain subclasses. Five of the seven cryoglobulins studied were positive in at least two of the three tests used to assay for anti-gamma-globulin activity. One protein was only weakly positive in one test system and another was negative in all test systems. The structures which were recognized by the cryoglobulins were localized to the Fc-fragment. Only primate gammaG-globulins contained these antigenic determinants and in some cases the cryoglobulin appeared to show specificity for one human heavy chain subclass over the others. Antigenic analysis revealed that four of the five cryoglobulins with definite antibody activity belonged to the gammaG3-subclass, the fifth belonged to the gammaG1-subclass. The two cryoglobulins which reacted only weakly or failed to combine with gammaG-globulins were both of the gammaG1-subclass. These findings taken together with the localization of the combining site to the Fab-fragment suggests that many of these cryoglobulins may represent antibodies to gammaG-globulin, and that the cryoprecipitate in these cases represents antigen-antibody complexes of such a nature that they precipitate only in the cold.

Two-dimensional polyacrylamide gel electrophoresis analysis of cryoglobulins and identification of an IgM-associated peptide

The clonality of immunoglobulins (Igs) in cryoprecipitates (n = 41) was studied by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). Our series included 24 cryoglobulins characterized by immunofixation electrophoresis (IF), 12 'trace amount' cryoglobulins, defined by a protein content in the precipitate of less than 0.05 mg/ml of serum, and five cryoglobulins of undetermined protein composition by IF. 2-D PAGE analysis showed polyclonal IgG associated either with monoclonal Igs (type II cryoglobulins; n = 14) or with polyclonal IgM (type III cryoglobulins; n = 14). In ten cryoprecipitates (two 'trace amount' cryoglobulins as well as seven of 19 type II and as one of five type III cryoglobulins by IF) polyclonal IgG were associated with a mixture of polyclonal and monoclonal IgM. These cryoglobulins were tentatively named type II-III cryoglobulins. A monoclonal IgM was observed in one cryoprecipitate (type I cryoglobulins). Two cryoglobulins presented unexpected 2-D patterns, characterized by the presence of oligoclonal IgM, with trace amounts of Igs of different isotypes (tentatively named type II-III(variant) cryoglobulins). A peptide of 44 kDa with a pI of 5.45 was observed in all cryoglobulins containing IgM (n = 40). This peptide was also present in purified monoclonal or polyclonal IgM fractions. N-terminal microsequencing (12 amino acid residues) revealed that this IgM-associated peptide was an unknown protein. Our results highlight the role of 2-D PAGE as an aid in the analysis of cryoglobulins.

Cryoglobulinemia

A large number of disease states are characterized by cryoglobulinemia. Quantification and immunochemical classification of cryoglobulins in serum provide information of diagnostic and pathophysiologic utility. Thus, type I cryoglobulins consist of a monoclonal immunoglobulin of a single class and are associated with lymphoproliferative disorders, such as multiple myeloma. Type II (mixed) cryoglobulins contain monoclonal IgM or rheumatoid factor and polyclonal IgG, and occur in patients with Waldenstrom's macroglobulinemia or chronic active hepatitis, for example. In type III cryoglobulins, both the IgM and rheumatoid factor and the IgG components are polyclonal. A large number of autoimmune or infectious diseases exhibit type III cryoglobulinemia. In certain well-studied situations, type II and type III cryoglobulins have been shown to contain antigen-antibody complexes directly involved in tissue injury in vivo, e.g., DNA and anti-DNA in systemic lupus erythematosus.

Analysis and general classification of serum cryoglobulins by capillary zone electrophoresis

The analysis and general classification of serum cryoglobulins (CG) by capillary zone electrophoresis (CZE) are described. This technique allowed the introduction of several new aspects to the analysis of CG: (i) direct detection of monoclonality of the gamma-globulins and general classification of the different CG types, (ii) a tenfold decrease in sample size, (iii) direct quantification of the cryoprecipitate without the need for further chemical analysis, and (iv) mathematical correction for the coprecipitation to avoid extensive washing steps or falsely elevated results. In addition to that, since staining steps are avoided, the method is rapid and easy to perform. The method has the limitation of not being able to perform immunological characterization directly of the CG. One hundred and ninety-eight samples were analyzed by this technique. Many of the cryoprecipitates have a higher ratio of gamma-globulins/albumin when analyzed by CZE compared to analysis by agarose electrophoresis. Clinical examples are presented to illustrate the advantages of this method for the analysis of serum cryoglobulins.

Two-dimensional electrophoretic analysis of cryoproteins: a report of 335 samples

Cryoproteins are defined as proteins precipitating at low temperature. Most frequently, the precipitate contains immunoglobulins (Igs), and are therefore called cryoglobulins. Three types of cryoglobulins have been described: type I contains a single monoclonal Ig, whereas type II is a mixture of a monoclonal Ig with polyclonal Igs, and type III is a mixture of polyclonal Igs of different isotypes, most frequently IgG and IgM. Type II and type III are also called mixed cryoglobulins. A new type of cryoglobulins, containing polyclonal IgG associated with a mixture of polyclonal and monoclonal IgM has recently been described after two-dimensional polyacrylamide gel electrophoresis (2-DE). This type of cryoglobulin has been called type II-III cryoglobulin. In this study, we report on 2-DE analysis of 335 cryoproteins from patients with heterogeneous clinical conditions. In 69 out of 335 samples (20.7%), 2-DE revealed patterns that were inadequate to characterize the cryoproteins. Out of 335 (79.3%) cryoproteins, 266 were identified according to their two-dimensional patterns: 265 samples contained Igs and were diagnosed as cryoglobulins, and one sample consisted of fibrinogen, and was identified as cryofibrinogen. Among the 265 cryoglobulins, types I, II, and III were observed in 9 (3.4%), 69 (26%), and 116 (43.8%) cases, respectively, whereas type II-III was detected in 71 (26.8%) cases. Eleven of the latter consisted of oligoclonal Igs (IgM in 10 cases, IgA in 1 case) mixed with traces of polyclonal IgG. These cryoproteins were tentatively named type II-IIIvariant cryoglobulins. Taken together, our result clearly show that 2-DE is a suitable technique to analyze cryoproteins.

In vitro reactivity of cryoglobulin IgM and IgG in hepatitis C virus-associated mixed cryoglobulinemia

BACKGROUND/AIMS

Mixed cryoglobulinemia is frequently associated with chronic hepatitis C virus infection. We aimed to clarify the mechanism, kinetics and participating proteins in cryoprecipitate formation, which are still being debated.

METHODS

Eighteen patients with cryoglobulinemia were studied. Isolated serum cryoprecipitates and purified cryoglobulin IgM and IgG fractions were analyzed in vitro by turbidimetry for temperature-dependent complex formation. Immunoglobulin reactivity, i.e. in cryoprecipitates and in cryoglobulin-free sera, was studied using immunoblot and enzyme immunoassays. HCV RNA was detected by reverse transcriptase/polymerase chain reaction.

RESULTS

By turbidimetry, purified cryo-IgM precipitated (in the absence of HCV RNA) with cryo-IgG as well as with non-cryoglobulin IgG and with IgG Fc or F(ab')2 fragments. In contrast, purified cryo-IgG did not precipitate with non-cryoglobulin IgM. Anti-HCV IgG reactivity was found in cryoglobulin-free sera, in cryoprecipitates and in purified cryoglobulin IgG fractions. The respective titers were similar. Purified cryo-IgM did not react to HCV-encoded proteins. Binding of cryo-IgM to heterologous IgG was inhibited by intact IgG (up to a mean of about 52%) as well as by IgG Fc (33%) and F(ab')2 fragments (17%). Binding of cryo-IgM to IgG was enhanced at low temperature (4 degrees C vs. 37 degrees C), particularly for type III cryoglobulin IgM.

CONCLUSIONS

In hepatitis C virus-associated cryoglobulinemia the in vitro precipitate formation depended on cryo-IgM, while IgG appeared to act as an unspecific antigenic partner. Hepatitis C viral particles were probably not required. Cryo-IgM binding occurred primarily to intact IgG. Anti-HCV reactivity of either cryo-IgM or cryo-IgG was not necessary for precipitate formation. Regarding the pathogenesis, a direct hepatitis C virus protein-dependent stimulation of B-cells producing cryo-IgM seems to be unlikely.

A case of cryoglobulinemic gangrene in myeloma with fatal outcome despite successful skin grafting

Extensive necrosis of the skin, muscle and bone was produced after prolonged cooling in a case of myeloma with cryoglobulinemia. Skin grafting was beneficial.

Can cryoglobulins interfere with the measurement of IgM antiphosphatidylethanolamine antibodies by ELISA?

Clinical manifestations of the antiphospholipid antibody syndrome (APS) have been recently related to the presence of phosphatidylethanolamine antibodies (aPE). However, it is well known that some molecules such as cryoglobulins, immunoglobulins that undergo a reversible precipitation at low temperatures, may interfere with biological assays. With this in view, we report the case of a patient with APS who was positive for both IgM aPE and type III cryoglobulinemia. Moreover, we show for this patient a potential implication of aPE in the cryoprecipitate formation. To further analyze the potential association between cryoglobulins and aPE, and also the possible consequences for aPE assay, we selected 55 patients according to positivity for both IgM aPE and cryoglobulinemia. Determination of IgM aPE levels was made before and after removal of cryoprecipitate from the serum. Of the 55 selected patients, 52 (95%) presented no significant difference for IgM aPE levels before and after cryoprecipitation. These results were ascertained whatever the aPE levels and clinical status of the patient. Taken together, our results indicate that cryoprecipitation does not interfere in most cases (95%) with the dosage of IgM aPE. Thus, IgM aPE do not appear to be involved in the formation of the cryoprecipitate.

[Immunopathologic implications of cryoglobulins (author's transl)]

Cryoglobulins are proteins which appear in the serum of some patients. Their basic characteristic is their power to precipitate at low temperatures. In this work a review is made of the data presented by several authors in regard to the origin, isolation, classification, and precipitation mechanism, as well as of the factors which influence the cryoprecipitability. We also set out the most probable etiopathogenic theories and the possible clinical findings in those patients who have these proteins altered in their serum. Finally we comment on the treatment with special reference to penicillamine.

Immune complexes: characteristics, clinical correlations, and interpretive approaches in the clinical laboratory

Immune-complex-mediated injury is thought to play a role in diseases such as rheumatoid arthritis, systemic lupus erythematosus, serum sickness, various infectious diseases, and malignancies. With increased appreciation of the biological and pathological significance of circulating immune complexes has come efforts to develop appropriate techniques for identifying and measuring them. Common approaches exploit such phenomena as the attachment of complement components to antigen-antibody complexes, the presence of specialized receptors for immune complexes at the surface of cells, and the ability of rheumatoid factor to bind with immune complexes. This variety of assay systems for immune complexes has yielded abstruse results in numerous human pathological conditions. Unfortunately, these results seldom correlate with one another in a given disease. Thus, use of a panel of immune complex assays has been recommended. Indirect consequences of immune complex disease may still be appraised and evaluated with some confidence in clinical medicine: measurements of C3 and C4, cryoglobulins, serum viscosity, and turbidity of serum samples. Measurement of immune complexes may be useful in diagnosis, prognosis, and therapeutic monitoring, but it is the characterization of immune complexes that holds the greatest potential for better understanding of disease mechanisms.

Clinical implications of the types of cryoglobulins determined by two-dimensional polyacrylamide gel electrophoresis

BACKGROUND AND OBJECTIVE

Two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) is a new method which can be used to study cryoprecipitates from the sera of cryoglobulinemic patients. It led to the identification of a new type of cryoprecipitate, tentatively named II-III, characterized by polyclonal IgG associated with a mixture of polyclonal and monoclonal IgM. Some discrepancies with the conventional classification of cryoglobulins were revealed. The association of particular clinical features with the classification of cryoglobulins by 2-D PAGE is examined.

DESIGN AND METHODS

Sixty consecutive patients affected by cryoglobulinemic syndrome with mixed cryoglobulins were included in the study. All patients were evaluated for cutaneous, articular, hepatic, renal and nervous involvement. The washed cryoprecipitates were typed using both techniques: immunofixation electrophoresis (IFE) and 2-D PAGE.

RESULTS

Sixteen (6 cases of type II and 10 of type III by IFE) of 60 cryoprecipitates (26.6%) appeared as type II-III by 2-D PAGE analysis. Nine cases were classified differently by IFE and 2-D PAGE. Mixed cryoglobulins of type II-III were not associated with a particular clinical pattern. Examining the clinical findings in the mono group (those with monoclonal IgM alone) and the poly group (those with polyclonal IgM alone or polyclonal and monoclonal IgM) we found clearly significant differences: more severe liver involvement in the poly group, and higher cryocrit and creatinine values, lower C4 level and more severe purpura in the mono group.

INTERPRETATION AND CONCLUSIONS

Our results confirm the reliability of 2-D PAGE in characterizing cryoprecipitates. This sensitive method can demonstrate a higher number of monoclonal components, undetectable by IFE. Type II-III cryoglobulins are not associated with a particular clinical pattern. The presence or absence of polyclonal IgM in mixed cryoglobulins seems to be correlated with some clinical findings.

[Hepatitis C virus and mixed cryoglobulinemia in dialysis]

Prevalence of hepatitis C virus (HCV) varies in the dialytic population according to the geographic area (5-85%); the European average is 19%, with marked differences between dialysis units. The means of virus transmission is still not clear and represents one of the major management problems faced by dialysis units. US authors and European study groups have recently demonstrated a high level od HCV infection in patients with essential mixed cryoglobulinemia (EMC), suggesting that the virus plays an etiological role. The authors examined the correlation between mixed cryoglobulinemia and HCV and the possible etiological role of the virus in the pool of patients undergoing dialysis at the Centre. In September 1994 28/63 (44.4%) patients were found to be Ab anti-HCV positive (second and third generation ELISA); circulating cryoglobulins identified as Type II following immunofixation were found in 2/28 patients (7%) using centrifugation and cold incubation techniques. In the absence of the pathologies classically associated with cryoglobulinemia, the patients were diagnoses as suffering EMC. The HCV/EMC correlation in the dialysed population has been analysed in a limited number of studies, with discrepant results (0-47%). This paper highlights the association between HCV and EMC in 7% of chronic dialysed patients and given that the finding of anti-HCV Ab in serum solely documents previous exposure to the virus, we can only indirectly attribute an etiological role to HCV. The search for viral RNA in the serum, cryocrit and surnatant of patients found affected by EMC may provide additional etiopathogenetic information.

Mixed cryoglobulinemia in hepatitis C patients. GERMIVIC

Cryoglobulins are immunoglobulins that persist in the serum, precipitate with cold temperature and resolubilize when rewarmed. Types II and III are mixed cryoglobulins (MC), composed of different immunoglobulins, with a monoclonal component in type II and only polyclonal immunoglobulins in type III. Mixed cryoglobulins are associated with connective-tissue disease, malignant hematological disorder (type B lymphoproliferation) or obvious infectious process. Mixed cryoglobulinemia syndrome is characterized by the clinical triad of purpura, arthralgia and asthenia associated with type II or type III MC. The disorder is the consequence of an immune-complex-type vasculitis as supported by clinical features, analysis of the cryoglobulins, the usually depressed level of complement during the active phase of the disease, and the deposition of immunoglobulins and complement in the lesions. Such cryoglobulinemia vasculitis may involve numerous organs, particularly the peripheral nervous system and the kidneys. MC is frequently associated with clinical and biological evidence of liver disease. There has been some controversy about which comes first, MC or chronic liver disease, but it seems fairly clear that MC is often a manifestation of underlying chronic active or persistent hepatitis. In MC patients, the hepatotropic antigen(s) capable of triggering production of antibodies which can later form immune complexes has been sought for many years. In the last ten years, numerous studies have demonstrated that infection with hepatitis C virus is involved in the pathogenesis of most mixed cryoglobulinemia. This review analyzes the main published data on hepatitis C virus-mixed cryoglobulinemia, the role of liver alterations, the predictive factors associated with MC production in HCV patients and its symptomatic nature or not, and the different types of vasculitis associated with HCV chronic infection.

Systemic vasculitis in patients with hepatitis C

OBJECTIVE

To analyze the main characteristics of patients infected with hepatitis C virus (HCV) presenting with different types of vasculitis syndrome.

METHODS

We retrospectively compared 2 groups of patients with HCV presenting with systemic vasculitis: 10 with biopsy proven polyarteritis nodosa-type systemic vasculitis (PAN, Group 1) and 7 with mixed cryoglobulinemia syndrome (MC, Group 2).

RESULTS

Patients of Group 1 presented with different features than Group 2: life threatening systemic vasculitis (10 vs 0; p < 0.01), severe multifocal sensorimotor mononeuropathies versus distal moderate sensory polyneuropathies, malignant hypertension (5 vs 0; p = 0.04), cerebral angiitis (2 vs 0), ischemic abdominal pain (2 vs 0), kidney and liver microaneurisms (2 vs 0), increased erythrocyte sedimentation rate and C-reactive protein (7 vs 0; p < 0.01), renal insufficiency (5 vs 0; p = 0.04), HCV genotype 1b (3 vs 6; p = 0.06), and lower activity of chronic hepatitis (p = 0.02). Neuromuscular biopsies showed lesions of vasculitis in all patients, but the type of vasculitis was different in Group 1 compared to Group 2: medium size artery involvement (7 vs 0; p < 0.01), necrotizing vasculitis (10 vs 0; p < 0.01), and mononuclear cell infiltrate in perivascular areas (0 vs 7; p < 0.01). Using prednisone, plasma exchanges, and interferon-alpha, complete recovery was obtained in all PAN-type patients except one. In Group 2 patients, interferon-alpha did not have any effect on the peripheral neuropathy.

CONCLUSION

HCV infection may be associated with different types of systemic vasculitis, i.e., polyarteritis nodosa or mixed cryoglobulinemia. Because of differences in clinical and pathological features and therapeutic strategy, PAN-type vasculitis should be distinguished from MC-type vasculitis in HCV patients.

Hepatitis C virus infection and cryoglobulinaemia

Mixed cryoglobulins (CG) are serum proteins that precipitate at low temperature and are commonly classified into two types according to the presence (type II) or not (type III) of monoclonal immunoglobulins. Mixed CG are observed in a wide variety of diseases. Some mixed cryoglobulinaemia occurs without evidence of an underlying disease and is considered as essential mixed cryoglobulinaemia (EMC). Many studies have underlined the possible involvement of liver diseases in the pathogenesis of cryoglobulinaemia and particularly viral hepatitis. Recently, it has been shown that 50 to 80% of patients with EMC are in fact infected with HCV. It has also been shown that CG may be found in about 50% of patients infected with HCV. HCV-RNA genomic sequences are specifically concentrated in CG as well as IgG reactive with HCV-related proteins, and monoclonal IgM with rheumatoid factor (RF) activity. The monoclonal IgM RF detected in HCV infected patients is highly restricted to the same cross-idiotype OWAO. In addition to hepatocytes, HCV-RNA has been found in both peripheral blood and BM mononuclear cells. These cells could represent a reservoir of virus and may play a major role in viral persistence; they also could act as effectors of tissue injury in various organs. HCV shows high genomic variability. It is not clear whether these genetic variations have a significant clinical impact (i.e. severity of the disease) but there is evidence that they may influence both the efficacy of the host immune response and the interferon treatment response. The role of viral factors has been studied but a clear relationship between the presence of cryoglobulinaemia, the viral load or the HCV genotype have not been demonstrated. The frequency of clinical symptoms related to mixed cryoglobulinaemia reported in the literature is extremely variable according to the series. The striking association between HCV infection and mixed type II CG (usually considered as a benign lymphoproliferative disorder) and the occurrence of HCV infection in patients with NHL suggest that HCV could be involved in the pathogenesis of some malignant lymphoproliferative disease. The progression to malignancy probably involves the accumulation of multiple mutations facilitated by chronic antigenic stimulation. The efficacy of anti-viral treatment on both CG levels and related symptoms argue strongly that HCV is involved in the production of CG.