Independence of Allotypic Determinants and Antibody Specificity

Studies were carried out to ascertain whether the specificity of an IgG antibody molecule influences the expression of the full complement of determinants characteristic of a given allotype. The presence of determinants was measured by the capacity of a given IgG preparation to displace from anti-allotypic antibodies all of a reference 125I-Fab fragment, possessing the same allotype, but derived from a different source. The results indicated that all IgG molecules studied, including specifically purified antibodies, possess a full complement of determinants (a1, a3, b4) and suggest that the portion of the surface of the molecule comprising the antibody-combining site is independent of the region of the surface which combines with anti-allotypic antibodies.