The immunogenicity of dinitrophenylated polyacrylamide and the adjuvant effect of polyacrylamide

Dinitrophenyl-substituted polyacrylamide (PAAm-DNP) is weakly immunogenic in guinea pigs and rats. Only 2-mercaptoethanol-sensitive IgM antibodies are elicited, and no immunological memory in guinea pigs is appreciated. A 15000-fold carrier excess, given 6 days before an immunogenic dose of PAAm-DNP, does not impair the anti-DNP response. Different doses of PAAm failed to increase the level of natural anti-DNP or anti-sulfanilic acid antibodies, either in guinea pigs or rats. Nevertheless, when given together with sheep red blood cells. PAAm increases the anti-sheep red blood cell humoral immune response in rats. It is suggested from the above data that the PAAm-DNP immunogenicity is not accounted for by the 'two-signal' model of B-cell activation (via 'associative antibodies'), nor by a model that ascribes B-cell activation to the polyclonal B-cell activating properties of the carrier. However, the possibility that the adjuvant effect showed by PAAm plays a role in allowing the conjugate PAAm-DNP to be immunogenic, remains an open question, and must be further investigated.