The use of radioactive isotopes in immunological investigations. 9. The reactions of antisera to antigens containing multiple determinant groups

Abstract

The effect of washing serological precipitates with ice-cold saline was investigated. Adequate removal of non-specific protein was achieved by 2 or 3 washings; further washing removes traces of non-specific protein, or possibly antibody. Antisera to iodinated sulfone-treated ovalbumin (and horse serum globulins) were prepared, and their reactions investigated. The antisera were "exhausted" successively with antigens containing either iodine groups or sulfone groups, and with antigens containing both types of determinant groups. Amounts of antibody precipitated at each stage were determined. Precipitates obtained by treating one of these antisera with an antigen containing only the sulfone determinant group showed no significant capacity to combine with a 2d antigen containing only iodine determinant groups. The experimental results are discussed with respect to the nature of the specific combing sites (receptor areas) on the antibody molecules. It is concluded that these are relatively large areas, specifically adapted towards equally large areas of the surfaces of the antigen molecules, but that the degrees of adaptation of different parts of the receptor areas may vary considerably from molecule to molecule. The data suggest that it is unlikely that there is more than one such receptor area on each molecule of antibody.