Immune complex behaviour during prolonged plasma exchange in essential mixed cryoglobulinemia and systemic lupus erythematosus.

A number of immunological parameters were measured in 9 patients with essential mixed cryoglobulinemia and 12 patients with systemic lupus erythematosus undergoing plasma exchange alone or without cytotoxic drugs. Only cryocrit significantly decreased in the majority of patients with essential mixed cryoglobulinemia. In contrast, immune complex levels, measured in two different ways, did not change on the whole, although variable and unpredictable changes were often present in individual patients. Thus, these data do not support the view that the mechanism(s) of action of plasma exchange in these diseases is only due to the quantitative removal of circulating immune complexes, and qualitative changes in the immune complex moiety may also occur.