Expression of Immunoregulatory Molecules by Thyrocytes Protects Nonobese Diabetic-H2h4 Mice from Developing Autoimmune Thyroiditis

One approach to prevent tissue destruction by autoimmune attack in organ-specific autoimmune diseases is to protect the target tissue from autoimmune reaction, regardless of its persistent activity. To provide proof-of-principle for the feasibility of this approach, the immunoregulatory molecules, TNF-related apoptosis-inducing ligand (TRAIL) and indoleamine 2, 3-dioxygenase, were expressed in the thyroid glands using adenovirus vector in nonobese diabetic-H2(h4) mice that spontaneously develop thyroiditis. Mice were anesthetized, and the thyroid glands were exposed by neck dissection, followed by in situ infection with adenovirus vector (5 x 10(10) particles per mouse) twice or thrice, starting 1 d or 4 wk before mice were supplied with sodium iodine (NaI) water. After 8 wk NaI provision, the extent of thyroiditis, serum titers of antithyroglobulin antibodies, and cytokine expression in the spleen were examined. In situ infection of adenovirus expressing TRAIL or indoleamine 2, 3-dioxygenase, but not green fluorescent protein, significantly suppressed thyroiditis scores. However, antithyroglobulin antibody titers and expression levels of cytokines (interferon-gamma and IL-4) in the spleen remained unaltered. Importantly, adenovirus infection 4 wk after NaI provision was also effective at suppressing thyroiditis. The suppressive effect of TRAIL appears to be mediated at least partly by accumulation of CD4(+)Foxp3(+) regulatory T cells into the thyroid glands. Thus, localized expression of immunoregulatory molecules efficiently protected the thyroid glands from autoimmune attack without changing the systemic autoimmunity in nonobese diabetic-H2(h4) mice. This kind of immunological intervention, although it does not suppress autoimmune reactivity, may have a potential for treating organ-specific autoimmune diseases.