Mechanism of antibody biosynthesis—I isolation and physical chemical properties of the retained antigen

The distribution of 14C-DNP-BSA and 14C-DNP-PGM in the tissues of the rabbit is reported. The data show that after the advent of antibody production, antigen is retained primarily in the liver, spleen and lymph nodes. Fractionation by phenol of liver homogenates from immunized rabbits indicates that the retained form of the antigen is qualitatively different from injected antigen. Sedimentation in sucrose gradients of the ‘retained antigen’ fraction gave an average S value greater than that of the starting antigen which suggested that ‘retained fragment’ was associated with macromolecular material. Sedimentation analysis in CsCl gradient confirmed that all of the antigen present in the water phase and precipitable by alcohol after extraction with phenol was bound to RNA. Partition studies in a phenol-detergent-water system at different temperatures suggests that the RNA of the ‘Ag fragment-RNA’ complex has solubility properties characteristics of the messenger type of RNA. The relationship of fragmentation of antigen to the theory of subcomplementarity in antigen-antibody interactrions is reviewed and a new theory for the biosynthesis of polypeptide chains in γ-globulin molecules involving ‘antigen fragment-RNA’ complex and a sub-cistronic m-RNA from lymphocytes is proposed.