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Slowly sedimenting components with a sedimentation velocity of about 7S and reacting with specific antisera against IgM were found in six pathological human sera. Four of these came from patients with different forms of reactive macroglobulinaemia of infectious origin. Similar components were produced from purified IgM preparations by bacterial action, and to a lesser extent by spontaneous splitting at room temperature. The conditions for such a splitting were, however, absent for most of the sera investigated in this study. The possibility that slowly sedimenting IgM-like components are artefacts, is discussed. [ABSTRACT FROM AUTHOR]

An in vitro assay procedure for evaluating the antibody response to glomerular basement membranes, lung basement membranes and tendon fibrils indicated a sharing of identical or similar antigenic components. At least 70 per cent of the glomerular basement membrane-binding antibodies are absorbable by tendon fibrils, and eluates from such tendon preparations are not nephrotoxic. Within the species employed (man, rabbit and dog) for glomerular basement membrane sources, there appears to be no species specificity as regards the presence of the nephrotoxic component. Immunization of sheep with either canine or rabbit glomerular basement membrane leads to the elaboration of a haemagglutinin for the respective species. [ABSTRACT FROM AUTHOR]