Evidence for presence of lgG4 anti-immunoglobulin autoantibodies in all human beings Original Research Article

lgG4 anti-IgG autoantibodies were found to be present in all serum samples from a group of healthy people; IgG4 anti-lgA and anti-lgE were present in only 13 of 218 (6%) and 8 of 218 (3·5%) samples, respectively. These antibodies also showed affinities towards animal immunoglobulins. We suggest that lgG4 anti-lgA antibodies (the strongest found heterophilic immunoglobulins) are responsible for most artifacts obtained with commercial ELISA systems.