Engineering the immune system with particles, step-by-step.

Biomaterials-based strategies to engineer the immune system have gathered considerable attention the past decade and have opened new avenues for vaccine delivery and for modulating the immune system to fight cancer. This review highlights some of these strategies that involve well-defined particle-based delivery systems that are constructed in a multistep fashion. Particular attention is devoted to the design of micro and nanoparticles to deliver antigen and molecular adjuvants to antigen presenting immune cell subsets in lymphatic tissue.