Antigenic determinants in fragments of gamma globulin from rabbit serum.

Peptic digestion of fraction III from papain-digested rabbit serum gamma-globulin produces a variety of smaller fragments. Some are too large to pass through a dialysis bag, and these retain the capacity to precipitate with antiserum to rabbit gamma-globulin. Others pass through the bag and fail to precipitate with antibody, but they can inhibit the precipitation of antibody with fraction III. This indicates that antigenic determinants of the gamma-globulin molecule are carried in these fragments.