[Low molecular weight IgM in human sera (author's transl)].

During evolution of vertebrates 7S-IgM-antibodies are the first developed specific antibodies. In man monomeric IgM is not observed in sera of healthy newborns, children or adults. The detection of 7S-IgM in monoclonal gammopathies (Waldenström's disease 71.4%, IgA-myeloma 47.8%, IgG-myeloma 24.2%, benigne monoclonal IgA-gammopathy 37.5%, benigne monoclonal IgG-gammopathy 15.5%) autoimmune (SLE 26.6%, multiple sclerosis 18%, chronic atrophic gastritis 14%, chronic aggressive hepatitis 35%) and in some infectious diseases (virus hepatitis 25%) is believed to be an atavistic primary IgM response, occurring in case of elevated humoral immune reactions and disorders of lymphatic tissues.