Suppression of autoimmune diabetes by the use of transgenic plants expressing the β-cell autoantigen and immunoregulatory cytokine to induce oral tolerance

Induction of specific immunological unresponsiveness by feeding protein antigens is termed oral tolerance and may be a potential therapy for autoimmune diseases. While oral tolerance therapy may be both simple and effective, the requirement for large amounts of protein will limit clinical testing of autoantigens which are difficult to produce. Transgenic plants could help solve this problem. Transgenic plants have the potential to produce large amounts of mammalian antigenic proteins at very low cost. Moreover, transgenic plants, as in the case of oral tolerance induction, can also become an effective autoantigen delivery system without extensive purification, thus resulting in major cost reduction. Here, we discuss the production of the P cell autoantigen glutamic acid decarboxylase (GAD) as well as the immunoregulatory cytokine interleukin-4 (IL-4) in transgenic plants and their applications for prevention of autoimmune diabetes by oral tolerance.