[Discrete nature of the antibody affinity of immune sera and the importance of this factor for antigen binding].

After mixing an antibody immunosorbent with Pasteurella pestis monovalent capsular antigen the concentration of the antigen in the free and bound states was evaluated. In this study the test points on the graph were found to be located on the lines characterizing different groups of antibodies differing in their affinity. The verification of the discrete structure of antibody affinity in 10 lots of hyperimmune horse serum showed the truth of this suggestion. The analysis of the role played by different groups of antibodies in binding the antigen indicated the prevailing role of a high-affinity group, especially in the zone with the excess of antibodies.