Quantitation of red-cell-bound IgG in normal and pathologic states by an enzyme immunoassay (EIA) technique.

A simple EIA technique for the quantitation of red-cell-bound immunoglobulin (IgG) was devised and applied to normal and pathologic states, including autoimmune hemolytic anemia (AIHA) and other disorders. The mean red-cell-bound IgG value for normal subjects was 73.2 ± 25.8 ng/l0'o red cells (mean ± ISD). Fifteen patients with AIHA had an increased level of red-eell-bound IgG ranging from 109 to 10,000 ng/l0'o red cells. The concentration of red-eell-bound IgG in AIHA patients was well correlated with the percentage of reticulocytes in the peripheral blood and showed a rapid fall after the initiation of steroid therapy. Red-cell-bound IgG levels in Fisher-Evans syndrome, idiopathic thrombocytopenic purpura (lTP), systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and IgG myeloma measured by this technique are also presented. A significant correlation was found between red-cell-bound IgG levels and serum IgG levels in normal subjects and in patients with these pathologic conditions, except in the cases of AIHA and Fisher-Evans syndrome. The quantitation of red-ceil-bound IgG by this EIA technique is of great value for clarifying the pathophysiologic significance of red-cell-bound IgG in health and disease.