Regulation of the immune response: VI. Inability of F(ab′)

Intact IgG antibody can terminate established immune responses, whereas F(ab′) 2 antibody cannot do so. The difference between the two antibodies appears to be qualitative. F(ab′) 2 antibody, but not pepsin-digested normal serum, can interfere with the suppression and termination of immune responses induced by intact IgG antibody. These results are discussed in terms of the tripartite inactivation model.