THE RANGE AND FINE SPECIFICITY OF THE ANTI‐HAPTEN IMMUNE RESPONSE: PHYLOGENETIC STUDIES

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Abstract
SUMMARY: Heterodontus francisci(horned shark) andPseudopleuronectes americanus(winter flounder) were immunized with furyl‐oxazolone (furyl‐Ox) and phenyl‐oxazolone (phenyl‐Ox) coupled either to bacteria or protein carriers. The antibodies produced were measured by inactivation of furyl‐ or phenyl‐Ox conjugated bacteriophage, and their affinity and fine specificity were estimated by inhibition of phage inactivation with a series of structurally related hapten analogues. In both species, post‐immunization peak titres were 100 to 2000 times higher than preimmunization titres.A number of unique features distinguishedHeterodontusantibodies fromPseudopleuronectesor mammalian antibodies.Heterondontusantibodies exhibited a lower affinity for the immunizing hapten (furyl‐Ox or phenyl‐Ox) and a reduced ability to distinguish the homologous immunogenic hapten from its structural analogues. In addition,Heterodontusantibodies exhibited a lower level of inter‐individual variation in affinity and fine specificity than didPseudopleuronectesor mammalian IgM antibodies; this was especially prominent in anti‐furyl‐Ox responses. Typically the affinity and fine specificity ofHeterodontusantibodies did not change over the 146‐day period of immunization and were not influenced by the nature of the carrier. The implications of these findings in terms of the phylogenetic origins of antibody diversity are discussed.