Elevated IgM anti-IgE in sera from allergic patients

The role of anti-IgE autoantibodies in IgE-related allergic diseases has not been elucidated sufficiently. For example, anti-IgE antibodies have been reported to cause both proallergic and antiallergic blocking reactions. Contrary to other authors, some authors revealed a positive correlation between total IgE and the amount of IgE/IgG complexes detected. By comparing the IgE levels of allergic patients with those of control persons and rheumatoid arthritis patients the present study contributes to our understanding of the role of anti-IgE autoantibodies. The sera were tested by means of ELISA concerning their content of free and complexed IgG and IgM anti-IgE. In addition, the amounts of IgE/IgG and IgE/IgM complexes were determined in the sera of allergic and control persons after Superose 6 column separation. We found that the allergic patients revealed significantly higher values of free IgM anti-IgE than patients with rheumatoid arthritis and than control persons (mean 0.470, p = 0.0164 and p = 0.0061, respectively). The corresponding values for IgE/IgM complexes also tend to be higher (mean 0.431, p = 0.0784 and p = 0.0601, respectively). However, the corresponding contents of IgG anti-IgE autoantibodies and IgE/IgG complexes did not differ significantly. After Superose 6 column separation, we detected IgE/IgG in fractions corresponding to MW of 150 to 180 kDa for the sera of both allergic and control persons. In contrast, the IgE/IgM complexes were found in fractions corresponding to MW 330 kDa. We conclude that the increased IgM anti-IgE autoantibody titer in the sera of allergic patients is not correlated with the high total IgE level. Moreover, we suggest that the IgE/IgG complexes form de nova during ELISA. Unlike the IgE/IgG complexes, the IgE/IgM complexes are assumed to occur already in circulating blood.