cryoglobulin

a serum globulin (invariably an immunoglobulin) that precipitates at low temperature (e.g., 4°C) and redissolves at 37°C. Cryoglobulins are classified as Type I, monoclonal immunoglobulins; Type II, immune complexes involving monoclonal immunoglobulins with antibody activity against polyclonal immunoglobulins; or Type III, immune complexes involving polyclonal immunoglobulins (in most cases, these are globulin-antiglobulin immune complexes like Type II complexes). Types I and II occur in plasma cell dyscrasias and lymphoproliferative disorders as well as in asymptomatic “essential” cryoglobulinemia. Types II and III occur in autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, and Sjögren's syndrome. Type III also occurs in a wide variety of infectious diseases.