Prevention of homocytotropic antibody formation and anaphylactic sensitization by prefeeding antigen.

Studies were conducted in rats to determine whether pre-feeding antigen can prevent the development of Bordetella pertussis-induced homocytotropic antibody (HCA) formation and anaphylactic sensitization to the fed antigen. DA rats fed ragweed for a minimum of 2 wk and Sprague-Dawley rats fed horse serum for at least 4 wk demonstrated specific unresponsiveness to anaphylactic sensitization as measured by their inability to form HCA and their normotensive response to intravenous challenge with antigen. This state was more easily attained when feeding of antigen was started at the age of 30 days than at 90 or 150 days, and resistance to anaphylactic sensitization could be maintained by continued feeding of antigen. However, if anaphylactically sensitized to the fed antigen. The results suggest that induction of anaphylactic sensitization can be prevented by pre-feeding antigen.