SEROLOGIC STUDIES OF PROTEOLYTIC FRAGMENTS OF RABBIT AGGLUTINATING ANTIBODIES*

Abstract

Univlalent 3.5S fragments of rabbit 7S antihuman red cell agglutinating antibodies prepared with papain or pepsin and mercaptoethylamine reacted specifically with their homologous antigens, but failed to produce agglutination of the erythrocytes. Prior treatment of the cells with proteolytic enzymes or suspension in 30% albumin still failed to produce agglutination. Combination of the fragments with the homologous antigen was demonstrable by agglutination upon subsequent addition of chicken or goat antibody specific for the univalent fragments of rabbit gamma-globulin. Similar results were obtained with univalent fragments of rabbit antibody to human gamma-globulin by use of human cells sensitized with human gamma-globulin. The results are consistent with current theories as to the mechanism of action of bivalent and univalent antibodies, and provide another example of the properties of univalent sub-units of antibody.