Studies of retroorbital tissue xenografts from patients with Graves' ophthalmopathy in severe combined immunodeficient (SCID) mice: Detection of thyroid-stimulating antibody

The pathogenesis of Graves' ophthalmopathy (GO) is still unclear and the possible role of TSH receptor antibody in the development of GO is controversial. However, the recent availability of severe combined immunodeficient (SCID) mice has provided a means to study of human autoimmune thyroid disease in an in vivo environment. In the present study, we xenografted human retroorbital (RO) tissues from 9 patients with GO into 9 SCID mice and the autologous peripheral blood mononuclear cells (PBMC) from 5 of 9 GO patients were engrafted into 5 separate SCID mice to reconstitute the immunological environment of human GO. Mice blood samples were taken every 2 weeks for the measurements of human IgG, thyroglobulin antibody (Tg-Ab), thyroperoxidase (TPO)-Ab, thyroid-stimulating antibody (TSAb), and interferon-gamma (IFN-gamma). Eight weeks after xenografting, mice were killed; RO tissues were analyzed histologically. SCID mice with RO tissues from 2 of 9 GO patients produced human IgG peaking at 6-8 weeks after xenografting. TPO-Abs and TG-Abs were detectable in low titer in mice with RO tissue xenografts from 3/9 and 4/9 GO patients, respectively. The mean level of IFN-gamma in SCID mice with GO RO xenografts was higher than that of a control subject (RO tissue from a non-GO patient). TSAbs were actually produced from 7 of 9 mice xenografted with GO RO tissues, and reached their peaks at 2-8 weeks after xenografting; autologous PBMC (alone, without RO tissues)-engrafted SCID mice did not produce any detectable level of TSAb. The control mouse did not produce any detectable levels of human IgG, TPO-Ab, Tg-Ab, or TSAb. Immunohistochemical analysis of orbital mononuclear cell infiltrates revealed a predominance of T lymphocytes, with a small percentage of B lymphocytes in GO RO tissue graft. In conclusion, we have successfully reconstituted the SCID mice with human lymphocytes of RO tissues from patients with GO. Autoreactive B cell clones responsible for secreting TSAb exist in GO RO tissue and may be a key factor in the initiation and/or the progression of GO.