Complement activation by cryoglobulin. Evidence for a pathogenic role of an IgG (kappa) cryoglobulin in cutaneous vasculitis

Abstract

A cryoglobulin isolated from the serum of a patient with cutaneous vasculitis and its interaction with the complement (C) system was analysed. Whole C activity and the activities of C1, C2 and C4 in the patient's serum were completely absent, C3 was completely converted into haemolytically inactive beta 1A. In vitro, the cryoglobulin was highly active in consuming C. The isolated cryoglobulin interacted with the C system in a way similar to immune complexes. It consumed preferentially the first C components, while the late-acting components were barely affected. C consumption and C3 conversion were maximal at temperatures around 20°C. The data suggest, that cryoglobulin by activating the C system in vivo may cause tissue injury in a similar manner as has been described for immune complexes.