Biomaterials are emerging as a powerful tool for harnessing adaptive immunity in the treatment of infectious disease, cancer, and autoimmunity, as well as to improve tissue engineering design and transplantation. This two-part symposium welcomes biomaterial-based strategies focused on directing adaptive immune response toward either immunity or toward tolerance. Representative examples include activation of reactive T cells and B cells for vaccination or immunotherapy, generation of regulatory T cells to promote immune tolerance, or other strategies involving antigen or self antigen-specific responses. Studies employing microparticles, nanoparticles, self-assembled materials, engineered structures, and/or biomedical devices to control these events are all appropriate for this symposium. Reports with a disease focus or translational aspect are particularly encouraged, but mechanistic studies investigating the interactions between biomaterials and immune cells or tissues are also welcome.