Subclasses of warm autoantibody IgG in patients with autoimmune hemolytic anemia and their clinical implications

Objective To explore the mechanism of autoimmune hemolysis and establish a more sensitive test for autoimmune hemolytic anemia (AIHA). Methods IgG subclasses were tested in 40 patients with idiopathic or second ary AIHA by Coombs test with monoclonal antibodies. Hb, TBiI, RC and FHb, a s hemolytic parameters, were used to analyze the clinical implications of s ubclasses of AIHA warm autoantibody IgG. Results In most patients IgG incomplete warm autoantibody was IgG1 (27 pati ents), but IgG3(20 patients), rarely IgG2 (14 patients) and IgG4(9 patients ) also occurred. Three groups were analyzed: Group A included 20 patients w ith IgG3; Group B included 14 patients with IgG1 but without IgG3; Group C included 6 patients without IgG1 and IgG3. There were significant differenc es (P < 0.01) between groups in Hb, TBiI, RC and FHb. Moreover, we also fou nd that the sensitivity of Coombs test with polyclonal antiserums was 90.0% , while that of Coombs test with monoclonal antibodies was 97.5%. The effec t of treatment was worst in patients with positive IgG3 autoantibody, whose hemolysis recurred frequently. Conclusion IgG3 autoantibody was the most effective in bringing about red c ell destruction, IgG1 autoantibody was less effective, IgG2 even less, wher eas IgG4 autoantibody was shown to hardly affect red cell survival. Coombs test with monoclonal antibodies was more sensitive than that with polyclona l antiserums. Patients' respondence to treatment correlated with the type o f IgG subclasses.