4. 自己免疫性溶血性貧血における抗赤血球自己抗体の定量と病態解析

β-ガラクトシダーゼ標識酵素免疫測定法による赤血球結合免疫グロブリン定量を中心として

抄録

A sensitive enzyme-linked immunoassay technique for the quantitation of red cell-bound immunoglobulins (IgG, IgA and IgM) was devised and applied to quantitating red cell-bound immunoglobulins in normal and pathologic states including autoimmune hemolytic anemia (AIHA) and other disorders. Red cells from normal subjects gave values (mean±1SD, ng/10¹⁰ red cells) of IgG 73.2±25.8, IgA 23.6±8.2 and IgM 14.3±7.5, respectively. Fifteen patients with AIHA had an increased level of red cell-bound immunoglobulins of three calsses: IgG 3114.2±3074.3, IgA 84.8±79.9, and IgM 398.9±540.6. The concentrations of red cell-bound IgG in AIHA patients correlated well with the reticulocyte percentage in peripheral blood and showed a rapid fall to a certain level after the initiation of steroid therapy, indicating that the amount of autoantibodies on red cells is one of the major determinants of the rate of hemolysis in vivo in AIHA. Young red cells, separated by Percoll density gradient centrifugation from the peripheral blood of AIHA patients, contained less red cell-bound IgG concentration than the old cells. It was also found that marrow erythroblasts from AIHA patients have very low binding capacity of IgG coated immunobeads in comparison to the high binding capacity of their peripheral red cells. These facts suggest that the antierythrocyte autoantibody in AIHA has less affinity to the membrane of young red cells. Red cell-bound immunoglobulin levels in Fisher-Evans syndrome, ITP, SLE, RA and IgG myeloma by this technique were also presented and their pathophysiologic significance in each disorder is discussed. The results obtained in this study gave us basis for clarifying physiologic as well as pathophysiologic significance of red cell-bound immunoglobulins in health and disease.