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SEQUENTIAL CHANGES IN T H E RELATIVE AFFINITY OF ANTIBODIES SYNTHESIZED DURING T H E IMMUNE RESPONSE

The antibodies that are isolated from a rabbit's serum after immunization with dinltrophenylated proteins are heterogeneous with respect to their affinity for dinitrophenyl ligands. In addition, the average affinity increases markedly with time after antigen administration (1). Thus, when anti-dinitrophenyl antibodies specifically purified from serum obtained 8 wk after immunization were compared with those from serum obtained 2 wk after immunization, at least a 100-fold increase in average association constant was observed. The increase in affinity was shown to be related to the quantity of antigen administrated: large amounts delayed the change (1). However, serum antibodies of a particular specificity are a mixture of molecules synthesized at different times and subject, perhaps, to varying rates of elimination from the circulation. Moreover, the isolation of antibodies from serum may result in some degree of selection of certain antibody molecules at the expense of others. Thus the purified antibody may contain, preferentially, molecules that are more easily precipitated by antigen or that are eluted more efficiently from precipitates. In order to determine the properties of all the antibody molecules formed at any particular time it seemed desirable, accordingly, to obtain antibodies directly from the antibody-forming cells themselves. Antibody synthesis generally takes place mainly in the lymph nodes draining sites of antigen injection (2-4). Studies were initiated therefore to determine the binding properties of the anti-DNP 1 molecules formed in vitro by suspensions of ceils obtained from the axiilary and popliteal lymph nodes of rabbits