Adjuvant activity of non-ionic block copolymers. IV. Effect of molecular weight and formulation on titre and isotype of antibody.

The adjuvant activity of block copolymers varies with the lengths of the chains of polyoxypropylene (POP) and polyoxyethylene (POE). This project evaluated the adjuvant activity of new copolymers with long polyoxypropylene chains in mice immunized with TNP-hen egg albumin in 2% squalone-in-water emulsions. Two of the new copolymers, L141 and L180.5, not only stimulated higher antibody titres to TNP than older preparations, but also induced a higher percentage of the IgG2 isotypes. The smaller older copolymers, L101 and L121, induced higher absolute levels of IgG3 antibody and relative increases in IgG1. Incorporation of immunomodulators (cell wall skeletons, monophosphoryl lipid A or threonyl muramyl dipeptide) increased mean IgG titres but also increased variability of responsiveness among individuals.