Addenda

Abstract

The studies concerned with the ability of bradykinin-polylysine antibody to recognize bradykinin analogs and fragments have been extended by the use of anti-bradykinin ovalbumin and an antiserum directed against human kininogen I which recognized the bradykinin moiety of the immunogen [FISCHER et al.: Biochemistry 8, 3750 (1969)]. The antibodies directed against bradykinin coupled to ovalbumin showed marked antibody heterogeneity when bradykinin analogs and fragments were examined. These antibodies seem to require the presence of the aryl residues to a far greater extent than does anti-bradykinin polylysine. However, experiments using bradykinin fragments indicate that both these antibodies require the entire nonapeptide sequence for binding to antibody. Binding inhibition was also examined using antibody directed against human kininogen I, the low molecular weight precursor of bradykinin which contains the kinin moiety at its carboxy terminus in the same orientation in which it is covalently bound in the other two immunogens. The binding inhibition results indicate that this antibody population was also heterogeneous, but unlike the other two antibodies used, recognizes mainly the carboxy terminal residues of the bradykinin sequence. The analog and fragment binding data using all three antibodies allow the conclusion that the nonapeptide bradykinin may behave as an integral antigenic determinant, and that its conformation is of some importance. The role of the carriers in the immunogens has been considered, particularly with regard to electrostatic effects, and suggests that the degree of homogeneity of the antibodies produced reflects the heterogeneity of the immunogenic stimulus.