The companions: regulatory T cells and gene therapy.

Undesired immunological responses to products of therapeutic gene replacement have been obstacles to successful gene therapy. Understanding such responses of the host immune system to achieve immunological tolerance to a transferred gene product is therefore crucial. In this article, we review relevant studies of immunological responses to gene replacement therapy, the role of immunological tolerance mediated by regulatory T cells in down-regulating the unwanted immune responses, and the interrelationship of the two topics.