Stimulation and Suppression of the Innate Immune System through Nanotechnology

Nanoparticles (NPs) are growing as a suitable option to treat and diagnose several diseases because of their inherent physicochemical properties and their capacity to deliver drugs and function as controlled drug release/delivery systems. Nevertheless, instead of reaching the desired target, most of the NPs are often trapped inside innate immune cells, in a process that represents one of the longstanding bottlenecks of nanomedicine. This fact, which could be seen as a disadvantage at first glance, has become a great opportunity to modulate the response of the immune system by taking advantage of this “pseudospecific” direct interaction between immune cells and NPs. Immunotherapy has recently emerged as a revolutionizing cancer therapy, awakening the immune system to overcome the immune suppression associated with tumors. Beyond cancer, activation of the immune system can be desirable in cases of infection. On the other hand, suppression of the immune system is a needed strategy in the case of autoimmune diseases, allergies, and after tissue transplantation. In this review, we explore the inherent immunoreactive nature of NPs and the advances in NP engineering to intentionally modulate the immune response, either by eliciting immunostimulation and pro-inflammatory responses or by inducing immunosuppression.