Studies on the immune response to fixed antigens. II. Optimal conditions for inducing and eliciting helper function by fixed antigens and the mechanism responsible for this effect.

Heavily trinitrophenylated sheep red blood cells (RBC) (TNP128SRBC) and glutaraldehyde-treated SRBC (G-SRBC) induced helper function. This helper function could accelerate anti-SRBC and anti-TNP secondary responses to subsequent challenge with TNP0.14SRBC in different strains of mouse. Preferential induction of helper function over primary antibody response was obtained with fixed antigens only. High doses of fixed RBC (4 X 10(7) or 4 x 10(8)/mouse) could induce optimal helper function and high doses of the challenger TNP0.14SRBC (4 X 10(7) or 4 x 10(8)/mouse) could optimally recall this function and stimulate secondary responses. G-SRBC was a better inducer of helper function than low doses of nonmodified SRBC. TNP128SRBC-primed mice produced a significant anti-SRBC response after subsequent challenge with TNP0.14 mouse RBC. Reverse help was suggested as one of the possible mechanisms of this response. Early helper function which developed four days after priming with TNP128SRBC or G-SRBC could be transferred to irradiated recipients with T, but not B, cells. Late immunologic memory which appeared 18 days after priming with TNP128SRBC could be transferred to irradiated recipients only with a mixture of T and B cells.