Homing of 51Cr-labeled human peripheral lymphocytes to Graves' thyroid tissue xenografted into SCID mice

Insight into Graves' hyperthyroidism from animal models

Graves' hyperthyroidism can be induced in mice or hamsters by novel approaches, namely injecting cells expressing the TSH receptor (TSHR) or vaccination with TSHR-DNA in plasmid or adenoviral vectors. These models provide unique insight into several aspects of Graves' disease: 1) manipulating immunity toward Th1 or Th2 cytokines enhances or suppresses hyperthyroidism in different models, perhaps reflecting human disease heterogeneity; 2) the role of TSHR cleavage and A subunit shedding in immunity leading to thyroid-stimulating antibodies (TSAbs); and 3) epitope spreading away from TSAbs and toward TSH-blocking antibodies in association with increased TSHR antibody titers (as in rare hypothyroid patients). Major developments from the models include the isolation of high-affinity monoclonal TSAbs and analysis of antigen presentation, T cells, and immune tolerance to the TSHR. Studies of inbred mouse strains emphasize the contribution of non-MHC vs. MHC genes, as in humans, supporting the relevance of the models to human disease. Moreover, other findings suggest that the development of Graves' disease is affected by environmental factors, including infectious pathogens, regardless of modifications in the Th1/Th2 balance. Finally, developing immunospecific forms of therapy for Graves' disease will require painstaking dissection of immune recognition and responses to the TSHR.

Lymphocyte homing in xenotransplanted human thyroid tissue can be inhibited by LFA-1 and ICAM-1 antibodies

OBJECTIVES

Homing of lymphocytes is an important factor with respect to the initiation of the autoimmune process in Graves' disease (GD). As previously shown, human lymphocytes, particularly of intrathyroidal origin, derived from patients with GD, are able to migrate into normal xenotransplanted thyroid tissue and induce functional and histological changes. The aim of this study was to investigate the effect of LFA-1 and ICAM-1 antibodies on the homing of lymphocytes of different origin into xenografted human thyroid tissue.

METHODS

Eighty-five nude mice bearing 8-week-old xenografts of normal human thyroid tissue were treated twice with anti-CD 54 (anti-ICAM-1), anti-CD 11a (anti-LFA-1), a combination of both, or, serving as controls, iso-antibodies without specific binding capacity or saline. Thereafter, intrathyroidal (ITL) or peripheral blood lymphocytes (PBL) obtained from 4 patients with GD or saline were injected into the animals (i.v., 0.2 mL, 10(6) cells). After 48 hours the mice were sacrificed and transplants as well as mice thyroids were examined by immunohistochemical staining with Ki67, CD3, HLA-II (DAKO, Hamburg), IgG, CD44, ICAM-1, and VCAM-1 (Immunotech, Hamburg).

RESULTS

Pretreatment with anti-ICAM-1 and anti-LFA-1 decreased lymphocyte homing (CD3-staining), and expression of HLA-II, IgG, CD44, and VCAM-1 in the transplants.

CONCLUSION

Our data show that [ICAM-1/LFA-1 stimulated (induced)] lymphocyte homing and subsequently thyrocyte proliferation are inhibited by ICAM-1 and LFA-1 antibodies in xenotransplanted thyroid tissue. This suggests that ICAM1 and LFA-1 play an important role in the early steps of autoimmune thyroid disease. The inhibition/suppression of ICAM-1 and LFA-1 interaction by respective antibodies, as demonstrated in the present study, may provide a new concept for prophylaxis and therapy.

Expression of intracellular adhesion molecule-1 and vascular cell adhesion molecule-1 and homing factor CD44 after engraftment of Graves' lymphocytes in xenotransplanted human thyroid tissue in athymic nude mice

The expression of adhesion molecules on thyrocytes and endothelium cells plays an important role in the pathogenesis of Graves' disease (GD). The intercellular adhesion molecule-1 (ICAM-1), the vascular cell adhesion molecule-1 (VCAM-1), and the homing receptor CD44 are responsible for the specific migration of lymphocytes in autoimmune thyroid diseases (AITD) (homing). Eight weeks after transplantation of thyroid tissue from 26 patients with nonautoimmune thyroid disease (nontoxic nodular goiter [NTG]) into nude mice, peripheral (PBL) and intrathyroidal lymphocytes (ITL) from 14 patients with NTG and 12 patients with GD were grafted into the animals. Two days after lymphocyte engraftment, the thyroid transplants were examined histologically (HE) and immunohistologically stained with monoclonal antibodies directed against ICAM-1, VCAM-1, and CD44. After injection of GD lymphocytes, thyroid transplants expressed significantly more ICAM-1, VCAM-1, and CD44 than after injection of NTG lymphocytes. This expression was even more pronounced after grafting of GD intrathyroidal lymphocytes. Our data demonstrate that only GD lymphocytes induce the expression of adhesion molecules and homing factor CD44, both of which play an important role in the migration of lymphocytes and induction of the autoimmune process.

Immunologic effects of human peripheral and intrathyroidal lymphocytes on xenotransplanted human thyroid tissue in athymic nude mice

T cells are intimately involved in the etiology and pathogenesis of human autoimmune thyroid disease. In order to further elucidate the immunologic mechanisms leading to Graves' disease (GD), we investigated the effects of human lymphocytes derived from patients with autoimmune and nonautoimmune thyroid diseases on human thyroid tissue xenotransplanted into nude mice. Eight weeks after transplantation of thyroid tissue from 26 patients with nonautoimmune thyroid disease (nontoxic nodular goiter [NTG]) into nude mice, peripheral (PBL) and intrathyroidal lymphocytes (ITL) from 14 patients with NTG and 12 patients with GD were engrafted into the animals. ITL and PBL subsets were analyzed by flow cytometer before engraftment. Two days after lymphocyte engraftment, the thyroid transplants were examined histologically (HE) as well as immunohistologically by staining with monoclonal antibodies directed against CD3 (T-cell activation and signal transduction), immunoglobulin G (IgG), HLA class II and CD31 (human endothelium). After injection of GD lymphocytes, thyroid transplants contained significantly more CD3, HLA class II, and CD4 expressing cells. Engrafted PBL and especially ITL from patients with GD specifically migrated into human thyroid transplants but not into the mouse thyroids, induced expression of class II products and led to IgG production by plasma cells. Persistence of human endothelium has been proven by positive CD31 staining. In conclusion, our data demonstrate that an organ-specific immune response is induced only by GD lymphocytes that migrate specifically into the thyroid transplants. Persistence of human endothelial cells in the transplants suggests that homing in this in vivo model reflects the situation in GD patients.

The autoimmune endocrinopathies the complexities continue to ravel

The organ-specific autoimmune endocrinopathies constitute a group of disorders related to one another and to some other nonendocrine autoimmune organ-specific diseases. Although there are genetic links between these entities, there are genetic differences as well; the suggestion of autoantigenic crossreactivity has not borne fruit and does not appear to explain these associations. Each condition may be due to a defect(s) in specific antigen-presenting genes, with consequential effects on specific T lymphocyte activation. Genetic overlap may explain poly-endocrine autoimmune disease or the appearance of different maladies in other family members. The immune response is extremely complex, but the many elements involved, and molecules that can interdict them, provide some promise for potential new therapeutic immunomodulatory interventions. (Trends Endocrinol Metab 1997;8:59-63). (c) 1997, Elsevier Science Inc.