Immunochemical characteristics of a particular cryoglobulin. A new cryoglobulin subgroup?

In a patient (BAR) affected by chronic active hepatitis we isolated a cryoglobulin constituted of polyclonal IgM (κ and λ) and a monoclonal IgG3 λ. The IgM represented the antibody of the cryoglobulin complex. This type of cryoglobulin, where the monoclonal component is the antigen and not the antibody, cannot be correctly classified using the nomenclature of Brouet et al. (1) currently in use. In this patient a two-year follow-up excluded any clinical signs of cryoglobulin toxicity. The immunochemical and clinical characterization of other cryoglobulins similar to BAR could establish a new homogeneous group.