Molecular basis for the temperature-dependent insolubility of cryoglobulins--XI. Sequence comparison of the heavy-chain variable regions of the human cryoimmunoglobulins McE and Hil by metric analysis

Cryoglobulinemic vasculitis: pathophysiological mechanisms and diagnosis

PURPOSE OF REVIEW

Cryoglobulins (CG) are immunoglobulins that precipitate in the cold, and dissolve at 37°C. In vivo, in cold exposed tissues and organs, they can induce vasculitis and occlusive vasculopathy after deposition on vascular endothelium under low temperature and high concentration conditions. Clinical manifestations are cutaneous (purpura, ulcers, vasomotor symptoms, and livedo reticularis), rheumatological (arthralgia and arthritis), and peripheral neuropathy (paresthesia and pain in the lower limbs). In profound organs such as the kidneys, CG deposition is less temperature-dependent, favored by local protein and anion concentrations, and can lead to glomerulonephritis. This review will focus on cryoglobulinemic vasculitis and vascular lesion, and their diagnosis.

RECENT FINDINGS

The mechanisms of vascular lesions of pathogenic CG in function of CG type and their characteristics are better defined. Optimal conditions for CG detection are critical. The importance of looking for underlying diseases, especially hepatitis C virus status in mixed CG, is reminded.

SUMMARY

A decision diagram for CG vasculitis diagnosis based on clinical and biological parameters is proposed.

Cryoglobulins: An update on detection, mechanisms and clinical contribution

Cryoglobulins are immunoglobulins precipitating in cold condition. They are classified in 3 types according to the Brouet classification and may lead to vasculitis of small and medium size vessels. Vasculitis is related to vessel obstruction by monoclonal cryoglobulin aggregates in type I cryoglobulins and immune complex deposition in type II and III mixed cryoglobulins. This phenomenon is favored by low temperature, especially in skin, joints, and peripheral nerves, or increased cryoglobulin concentration in kidneys. For their detection, collection and clotting at 37°C are critical pre-analytical conditions. Cryoglobulin characterization and quantification are important to identify the underlying disease. Since detection and identification of cryoglobulins lack standardization, a protocol for such detection, characterization and quantification is proposed.

Inhibition of cold insolubility of an IgA cryoglobulin by decanedicarboxylic acid and related compounds

Cold insolubility of a serum IgA cryoimmunoglobulin was found to be inhibited by the addition of 1.5 mM sodium decanedicarboxylate in vitro. The patient with the cryoglobulin had advanced multiple myeloma complicated by severe hyperviscosity that caused lethargy and episodic loss of consciousness. Decanedicarboxylic acid administered orally resulted in transient relief of symptoms and the loss of cryoprecipitability of the paraprotein. Further in vitro studies revealed that sodium salts of long-chain monocarboxylic acids with a minimum of eight carbons, and dicarboxylic acids with a minimum of 12 carbons inhibited cryoprecipitation. Salts of short-chain carboxylic acids, by contrast, enhanced cryoprecipitation. Sodium phenolate and sodium salts of benzoic acid, 2,4-DNP, phenylpropionic acid, and salicylic acid were also inhibitory. These latter compounds, which have a ring structure, did not cause precipitation at any concentration. It was demonstrated that the presence of a free carboxylic group was required for these activities; conversion of carboxylic acid to amide resulted in the loss of both the inhibitory and cryoprecipitation-enhancing effects. Normal plasma, or plasma from five other patients who had IgG, IgM, or mixed-type cryoglobulinemia, were not affected by any of these compounds. It is suggested that in selected cases of hyperviscosity syndrome associated with cryoglobulinemia, some of these compounds, especially monocarboxylic acids with appropriate chain lengths, or those with a ring structure, may have therapeutic applications.

Monoclonal IgM antibody exhibiting high-affinity binding and cryoglobulin properties

A monoclonal IgM antibody (18-2-3) derived from cell fusion of (NZB X NZW) F1 splenocytes following secondary immunization with fluorescein-conjugated keyhole limpet hemocyanin was shown to exhibit high intrinsic binding affinity and cryoinsolubility. Affinity-purified preparations were determined to be IgM by immunochemical, electrophoretic, and chromatographic analyses. An intrinsic association constant (Ka) of 2.9 X 10(10) M-1 (at 2 degrees C) was measured by first-order dissociation-rate analysis. Antibody solubility at low concentration (approximately equal to 50 micrograms/ml) was shown, by absorption spectroscopy, to be temperature dependent between 4 degrees C and 32 degrees C. Insolubility at low temperature (4 degrees C) was reversible in the presence of homologous fluorescyl hapten, indicative of active site involvement in the mechanism of cryoglobulin-18-2-3 complex formation. Characteristics of clone 18-2-3 are discussed in terms of (i) its potential use as a model for examining the mechanism of cryoprecipitation and (ii) the proposed relationship between affinity maturation and the IgM to IgG class switch.

Antibody response in Heterodontus

Appropriately selected phylogenetic models are capable of providing insight into genetic mechanisms which may have become obscured during the passage of evolutionary time. In higher vertebrates a complex multigenic family encodes immunoglobulin-variable regions. The mechanisms involved in the expansion of the gene family and the stable maintenance of large numbers of individual genes presently are not understood. By defining the nature of antibody diversity in lower vertebrate species, it may be possible to approach such issues at a more fundamental level. Analyses of the immunoglobulins in Heterodontus francisci (horned shark), a representative phylogenetically primitive elasmobranch, indicate that this species may represent a useful developmental model.