SPECIFICITY OF THE IMMUNE RESPONSE TO THE 2, 4-DINITROPHENYL AND 2, 4, 6-TRINITROPHENYL GROUPS : LIGAND BINDING AND FLUORESCENCE PROPERTIES OF CROSS-REACTING ANTIBODIES

The principal results of the present study are: (a) the failure to find an antibody subset that binds a cross-reacting ligand better than the comparable homologue in spite of the use of isolation methods that select for such antibody molecules; (b) the isolation of antibody subsets with virtually indistinguishable average intrinsic association constants for homologous and cross-reacting ligands, but which nevertheless have physical properties (Qmax and relative fluorescence coefficient) that readily distinguish these subsets according to their origin in response to antigenic stimulation with DNP- or with TNP-protein; (c) the demonstration, by precipitin reaction and measurement of association constants for homologous and cross-reacting haptens, of generally greater cross-reactivity among high affinity anti-DNP and anti-TNP antibodies, i.e. low affinity antibodies are generally more discriminating; (d) the selection of anti-DNP and anti-TNP antibody subsets that are distinctive in their ability to show spur formation in gel diffusion reactions with homologous and cross-reacting antigens. These results suggest that in the initial cellular response to antigenic stimulation, DNP-BγG and TNP-BγG stimulate virtually nonoverlapping sets of antigen-sensitive cells, despite the great similarity of these two immunogens. With prolonged stimulation this specificity wanes, giving rise to a more degenerate response evident in the greater cross-reactivity of the antibodies produced later in immunization.