Abstract
The in vitro T-cell proliferation induced by penicilloylated bovine IgG (BPO-BGG) in sensitized strain 2 guinea pigs could be specifically blocked by the serum of guinea pig (*305) which had been repeatedly immunized with BPO-BGG over a period of 9 mo. The antibodies which appeared in the serum of this animal (*305) were functionally similar to the strain 2 anti-idiotypic antibodies (a strain 2 BPO-BGG) raised by immunizing strain 2 guinea pigs with immuno-adsorbent column-purified BPO-BGG. Animal *305 had no detectable antibodies to BPO-BGG and failed to give a delayed hypersensitivity skin response when challenged with BPO-BGG.