Biodegradable microspheres. III: some immunological properties of polyacryl starch microparticles

The antibody responses against empty polyacryl starch microparticles and the corresponding human serum albumin (HSA)-containing microparticles were followed in mice for 30 weeks. Empty polyacryl starch microparticles were nonimmunogenic as determined by a direct, enzyme-linked immunosorbent assay (ELISA). However, when the previously nonimmunogenic particle matrix was presented to the immune system together with entrapped HSA, an antibody response was detected not only against the protein antigen, but also against the microparticles matrix as detected in an inhibition ELISA. The spheres were good adjuvants for the foreign protein (HSA) and gave nearly the same response as that obtained with Freund's complete adjuvant (FCA), while the corresponding free antigen showed no or poor immunogenicity. The effects of the microparticles on lymphocytes and macrophages were also investigated. Empty microspheres were weakly stimulatory to lymphocytes. Moreover, they stimulated macrophages to release interleukin 1 in vitro.