Spatial correlation between thyroid epithelial cells expressing class II MHC molecules and interferon-gamma-containing lymphocytes in human thyroid autoimmune disease

Cytokines and immune regulation in thyroid autoimmunity

We studied the role of cytokines and immune regulation in thyroid tissue from patients with Graves' disease. Immunohistochemistry showed that the thyroid glands are characterized by an aberrant expression of HLA class II antigens on thyrocytes, generation of new blood vessels and infiltration of mononuclear cells. We demonstrated that CD4+ memory cells were more frequent in thyroid glands from Graves' patients than were CD4+ naive cells. The intrathyroidal T cells demonstrated an enhanced expression of the adhesion molecules LFA-1, CD2, VLA-4 and VLA-5, and vascular endothelial cells of capillaries and thyrocytes in thyroid glands reacted with anti-ICAM-1 monoclonal antibody. The adhesion molecules and HLA antigens on both vascular endothelial cells and thyrocytes were regulated by inflammatory cytokines. These results suggest that circulating lymphocytes migrate into thyroid tissues and that memory T cells are retained in the thyroid tissues by cellular interactions with thyrocytes or with extracellular matrix.

A perspective on human autoimmune thyroid disease: is there an abnormality of the target cell which predisposes to the disorder?

It has been suggested recently that autoimmunity could be regarded as a physiological response of the normal immune system to autoantigens caught up in an inflammatory response to viral or bacterial antigen expressed in the target tissue. Other theories to explain autoimmunity include molecular mimicry whereby a viral or microbial hapten similar to an autoantigen initiates the production of autoantibodies that cross react with an autoantigen, with a subsequent immune response reacting with autologous cell structures which are homologous with the particular microorganism. There has also been a suggestion that there may be a genetic abnormality of the target cell which is necessary for the initiation of autoimmune thyroid disease. The present review examines these proposals and provides evidence against an antigen-driven origin for autoimmune thyroid disease (AITD). Currently, there is no valid evidence for viral involvement, and likewise the evidence for molecular mimicry as an initiating factor does not hold up to scrutiny. While a genetic abnormality of the thyrocyte may be important in certain animal models of AITD, in the human there is no evidence for such an abnormality. Evidence that AITD is derived from a disturbance of immunoregulatory mechanisms has been documented elsewhere and would appear to be the most appropriate explanation for these disorders. The immunoregulatory disturbance itself may be related to an abnormality of the mechanism of specific antigen (i.e. normal autoantigen) presentation to appropriately induce T lymphocytes and that theory will require further illumination.

Insulitis in type 1 (insulin-dependent) diabetes mellitus in man--macrophages, lymphocytes, and interferon-gamma containing cells

This study sought to determine, firstly, the relative frequency of lymphocytes and macrophages and, secondly, the percentage of lymphocytes containing interferon-gamma in inflamed islets (insulitis) of patients with type 1 (insulin-dependent) diabetes. Autopsy pancreases of 12 patients who had died of recent-onset type 1 diabetes and one pre-diabetic patient who had died of cardiomyopathy were examined immunohistochemically. In the 87 islets that were studied, the lymphocyte macrophage ratio was 9.7:1 and approximately 40 per cent of the lymphocytes contained interferon-gamma. Interferon-gamma release in the insulitis process may be involved in the pathogenesis of type 1 diabetes.

De novo HLA class II and enhanced HLA class I molecule expression in SV40 transfected human thyroid epithelial cells

Human thyroid follicular cells normally synthesize and express HLA Class I molecules but in glands affected by autoimmune or neoplastic diseases they express Class II molecules. We have investigated the effect of SV40 virus transformation on the expression of MHC molecules in human thyrocytes. Primary cultures of human thyroid from two different glands were transfected with the plasmid pX-8, containing the 'early' region of SV40 virus, and two continuous lines of thyrocytes were obtained. The cell lines maintained features of parental thyroid epithelial cells showing the characteristic cytokeratin filament network, microvillar protrusion and tight junctions. In addition, the SV40-transfected cells responded to graded doses of TSH with increased c-AMP production. Thyrocytes from both cell lines hyperexpressed Class I molecules and a significant proportion of them also acquired constitutive Class II expression, as determined by indirect immunofluorescence (IFL), flow cytometry and Northern blotting hybridization using a DR beta probe. These cells were found to be normally up-regulated by interferon (IFN)-gamma. Indirect IFL and flow cytometry analysis were used to detect and quantify the expression of HLA-DR, DP and DQ subregions. A co-ordinated expression (DR greater than DP much greater than DQ), reminiscent of the inappropriate HLA expression found in thyroid autoimmune disease in vivo and of the in vitro regulation in normal thyrocytes, was observed. Clones derived from these cell lines differed in their level of constitutive Class II expression and in their sensitivity to Class II induction by IFN-gamma. In conclusion, these thyroid cell lines could provide a useful tool for further investigation of HLA gene regulation in thyroid cells and for elucidating on the mechanism involved in the inappropriate HLA expression described in autoimmune and neoplastic diseases of the thyroid.