Immune complex cryoglobulinaemia in lepromatous leprosy: a pathogenetic approach to some clinical features of leprosy.

Cryoglobulins isolated from the sera of six patients with lepromatous leprosy were extensively studied by various immunochemical techniques. Immunoelectrophoresis and analytical ultracentrifugation revealed in all cases the presence of two components only, which were identified as IgG and IgM respectively. The IgG component of all six cryoprecipitates and the IgM component of five of them were polyclonal, whereas the remaining IgM component was monoclonal as it produced a narrow-banded electrophoretic spike and contained kappa light chains only. Anti-γ-globulin activity, detected in all sera and isolated cryoglobulins, was consistently found to be associated with the IgM fraction of the mixed cryoglobulins and was present at very high titres in the IgM monoclonal component. β serum levels were decreased in all cases. The cryoglobulins that appear to be immune complexes of the IgG/anti-IgG type may play a role in the pathogenesis of some clinical features of leprosy patients.