In vivo reprogramming of immune cells: Technologies for induction of antigen-specific tolerance.

Technologies that induce antigen-specific immune tolerance by mimicking naturally occurring mechanisms have the potential to revolutionize the treatment of many immune-mediated pathologies such as autoimmunity, allograft rejection, and allergy. The immune system intrinsically has central and peripheral tolerance pathways for eliminating or modulating antigen-specific responses, which are being exploited through emerging technologies. Antigen-specific tolerogenic responses have been achieved through the functional reprogramming of antigen-presenting cells or lymphocytes. Alternatively, immune privileged sites have been mimicked using biomaterial scaffolds to locally suppress immune responses and promote long-term allograft survival. This review describes natural mechanisms of peripheral tolerance induction and the various technologies being developed to achieve antigen-specific immune tolerance in vivo. As currently approved therapies are non-specific and carry significant associated risks, these therapies offer significant progress towards replacing systemic immune suppression with antigen-specific therapies to curb aberrant immune responses.