Distribution of antibody affinities. II. Fractionation of antibody with respect to its hapten binding affinity

Antibodies from individual sera were fractionated on the basis of their binding affinity by use of a specific immunoadsorbent. The distribution of affinities in the original serum and in each of the series of 10 fractions derived from it was computed. The antibodies were highly heterogeneous and generally not distributed in a symmetrical manner. The distribution of affinities varied with different immunizing conditions. It is clear from the data presented that while values for ‘average affinity’ generally reflect accurately the overall binding properties of an antibody sample, they do not provide a complete picture of the actual distribution of affinities present. It was found that antibody samples exist which are indistinguishable with regard to ‘average affinity’ but differ significantly with respect to the actual distribution of the antibody affinities. Detailed analysis of the binding curves indicated that even animals forming mainly high affinity antibody had considerable amounts of very low affinity antibodies present in their serum.