Antigen-binding activity and allergenicity of heterologous gamma-globulin absorbed from the rectum.

The molecular integrity of rectally absorbed antigens was studied in rats and mice. ABout 2% in the radioactivity of 125I-labelled horse gamma-globulin administered rectally reached the blood circulation. One fifth of this absorbed radioactivity (0.4%) reacted with anti-Fab antibody and about one eight (0.25%) of the original antigen-binding activity was maintained. The results indicated that a small but significant portion of the rectally administered proteins remained intact and retained the immunological function. Rectally-administered proteins induced IgE antibody responses in the rat and the mouse.