p-Azobenzenearsonate-L-tyrosine-mediated helper function in immune responses of guinea pigs and rats.

A small bifunctional antigen (4-hydroxy-5-iodo-3-nitrophenyl)acetyl-epsilon-aminocaproyl-L-tyrosine-azobenzene-p-arsonate [NIP-cap-TYR(ABA)] was found to induce fair humoral antibody formation against NIP-cap but very little anti-ABA-TYR. This was observed in rats and guinea pigs. Prior immunization with ABA-TYR, either as such or coupled to dodecanoylated bovine serum albumin (lipid-BSA), primed rats for an enhanced anti-NIP response to NIP-cap-TYR(ABA). An attempt to encourage rats to produce anti-ABA-TYR in response to the bifunctional antigen by priming them with NIP-cap-lipid-BSA failed. Priming with ABA-TYR was dose-dependent. An injection of 1.5-15 nanomoles per rat primed for an increased production of anti-NIP while 150 nanomoles did not. Adult thymectomized x-irradiated rats had a poor anti-NIP response to the bifunctional antigen if they were reconstituted with T-enriched lymphoid cells from control mice, but a good response if reconstituted with similar cells from ABA-TYR-primed syngeneic rats.