Characterization of Formaldehyde-Related Antibodies Encountered in Hemodialysis Patients at Different Stages of Immunization

. In hemodialysis patients who reuse formaldehyde-sterilized dialysers we found that antibodies agglutinating native NN red cells belonged exclusively to the IgM fraction of immunoglobulins. In the same patients antibodies directed against formaldehyde-altered NN red cells proved to be mainly IgG in addition to IgM. Three stages of formaldehyde-dependent RBC immunization could be distinguished serologically. The production of these antibodies was dependent on the time of hemodialysis treatment. We found antibodies which could bind complement in the presence of soluble antigen. These antibodies are supposed to damage the patient's red cells immediately after contact to minute amounts of formaldehyde during hemodialysis.