AGGLUTINATING EFFICIENCY AND COMBINING CAPACITY OF SHIGELLA AND VIBRIO ANTISERA FROM RABBITS AT DIFFERENT STAGES OF IMMUNIZATION

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Abstract
Studies of the relative combining capacites of different antisera to V. cholerae and S. flexneri were carried out using the Talmage test. In this test the absorption of an I131 labeled antibody preparation by antigen is blocked by the addition of unlabeled unknown serum. Sera from rabbits in the early stages of immunization ("early sera") had a high agglutinin titer but low combining capacity. Sera from hyperimmune rabbits ("late sera") had higher combing capacities than early antisera but similar or lower agglutinin titers. More antigen was needed to absorb the agglutinins from late antisera than from early ones of the same agglutinin titer, suggesting that late antisera contained relatively more antibody. At high concentrations, sera from hyperimmune rabbits agglutinated the homologous antigen more rapidly than did early antisera, even though early sera had similar or higher agglutinin titers. Sera drawn after the anamnestic response to bacterial antigen had the characteristics of late sera, i.e. their combining capacities were relatively high. The possible significance of these findings for in vitro estimation of protective antibody is discussed.