The Heterogeneity of Combining Sites of Antibodies as Determined by Specific Immunoadsorbents

[摘要] Anti-Xp antibodies labeled with radioactive iodine were fractionated by adsorption on the Xp-adsorbent and subsequent successive elutions either with increasing concentrations of p -nitrobenzoate (fractions I, III and V) or with single concentrations of o-, m - and p -nitrobenzoates (fractions O, M and P).Eluted antibodies were characterized by adsorption on three different immunoadsorbents containing the p -azobenzoate (Xp), p -azo- o -chlorobenzoate ( o -ClXp) or p ( p′ -azophenylazo)-benzoate groups (X′) and elution at various concentrations of each of six haptens, benzoate, p -nitrobenzoate, m -nitrobenzoate, p -aminobenzoate, o -chlorobenzoate and o -nitrobenzoate. The effectiveness of each hapten to elute antibody from the adsorbent was expressed as the logarithm of the reciprocal of hapten concentration required to elute 50% of antibody adsorbed (pEC50).The relative values of pEC50 between haptens differed from antibody fraction to antibody fraction, indicating that there is a difference of specificity among the antibody fractions. However, the order of pEC50 values of various haptens with each adsorbent was p -nitro- > m -nitro- > p -amino- = unsubstituted > o -chloro- > o -nitrobenzoates for all the antibody fractions as well as for the original unfractionated antibody.The order of pEC50 values of various immunoadsorbents was X′ > o -ClXp > Xp for the original unfractionated antibody fraction and fraction III, V, M and P, X′ > o -ClXp = Xp for fraction I and X′ = o -ClXp = Xp for fraction O. This reflects the difference among the antibody fractions with respect to the abilities to accommodate the o -substituent group and with respect to the extent of the contribution of the protein portion surrounding the haptenic group to their combination with the immunoadsorbent.

[学科分类] 生物科学（综合）