Administration of hyperimmune mouse anti-Shigella serum to newborn mice receiving a tolerance-inducing inoculum of Shigella soluble antigen (SSA) interferes with establishment of tolerance. An interval of 1 or 2 days between injection of antigen at birth and administration of antiserum results in only partial interference with tolerance, while an interval of several days or more results in no demonstrable effect. γ-Globulin containing fractions prepared from hyperimmune mouse serum is also

more »

... le of preventing induction of tolerance when administered at birth or shortly thereafter. Normal mouse serum, heterologous antiserum and hyperimmune anti-Shigella serum absorbed with Shigella organisms are ineffective. Administration of specific antiserum several weeks following induction of tolerance does not permanently "break" tolerance to Shigella. It is postulated that specific antibody to the tolerance-inducing Shigella antigen may combine with and/or neutralize the antigen in vivo in the newborn mouse so that no antigen remains free to induce and maintain tolerance.