Antibody-mediated suppression of the immune response in vitro. II. A new approach to the phenomenon of immunological tolerance.

Immunological tolerance to H antigens of Salmonella adelaide may be induced in vitro by the exposure of mouse spleen cells for 6 hr to an immunogenic dose of polymerized flagellin in the presence of low concentrations of specific antibody. Such antibody-mediated tolerance requires an optimal antigen: antibody ratio for its induction. A shift in this ratio in favor of the antibody concentration results in failure of tolerance induction and leads to immune suppression commonly known as antibody-mediated feedback inhibition which is not analogous to immunological tolerance. Fragment A of flagellin fails to induce immunological tolerance in vitro. Tolerance to polymerized flagellin may however be induced in vitro, provided the spleen cells are exposed to fragment A in the presence of specific antibody for 6 hr. The results are discussed in the light of current theories of the mechanism of tolerance induction.