Specificity of the immune response to the oestrone-azo-hapten structure

Comparison of the cross-reactions between 14 related steroids with eight antibodies showed that each antibody had its individual molecular specificity. During the 183-day period covering eight immunizations, cross-reaction between oestrone and 1-methyloestrone showed only very little change with five antibodies, while the great differences in cross-reactivity values for the individual antibodies were retained. With the same five antibodies, the course of cross-reaction between oestrone and 3-sulphooestrone as well as 6-oxooestrone was also fairly constant, the differences in cross-reactivity in relation to the individual antibodies being considerably large. The blood plasma antibody concentrations measured at the same intervals showed considerable fluctuation, whereas the affinity constants of the respective antibodies, except one of them, showed a moderate upward trend. The suggested molecular parameters of binding sites of the antibodies to the oestrone-4-azo-hapten structure were in surprisingly good agreement with those reported in the literature for mouse myeloma immunoglobulin A proteins possessing dinitrophenyl-binding activity. The individual antibodies exhibited highly sensitive radioimmunoassay curves for both oestrone and 3-sulphooestrone.