HLA-DM and invariant chain are expressed by thyroid follicular cells, enabling the expression of compact DR molecules.

Unitat d'Immunologia, Hospital Universitari Germans Trias i Pujol, Bellaterra, Barcelona, Spain.
International Immunology (Impact Factor: 3.14). 03/1999; 11(2):269-77. DOI: 10.1093/intimm/11.2.269
Source: PubMed

ABSTRACT Thyroid follicular cells (TFC) in Graves' disease (GD) hyperexpress HLA class I and express ectopic HLA class II molecules, probably as a consequence of cytokines produced by infiltrating T cells. This finding led us to postulate that TFC could act as antigen-presenting cells, and in this way be responsible for the induction and/or maintenance of the in situ autoimmune T cell response. Invariant chain (li) and HLA-DM molecules are implicated in the antigen processing and presentation by HLA class II molecules. We have investigated the expression of these molecules by TFC from GD glands. The results demonstrate that class II+ TFC from GD patients also express li and HLA-DM, and this expression is increased after IFN-gamma stimulation. The level of HLA-DM expression by TFC was low but sufficient to catalyze peptide loading into the HLA class II molecules and form stable HLA class II-peptide complexes expressed at the surface of TFC. These results have implications for the understanding of the possible role of HLA class II+ TFC in thyroid autoimmune disease.

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    ABSTRACT: One salient feature of autoimmune thyroid disease is the inappropriate expression of human leukocyte antigen (HLA) class II molecules by thyroid follicular cells. Metallothioneins (MT) are small proteins induced by tissue stress that can contribute to restoring homeostasis of tissue inflammation and have been found to be increased in a transcriptomic analysis of Graves' disease (GD) glands. To assess the role of MT in the pathogenesis of GD, we analyzed MT-I and -II expression and distribution in GD-affected thyroid glands (n = 14) compared with other thyroid diseases (n = 20) and normal thyroid glands (n = 5). Two-color indirect immunofluorescence and semiquantitative morphometry were applied. The relationship between MT and HLA class II expression was analyzed by their degree of colocalization in GD sections, and in vitro induction kinetics and expression of these molecules on the HT93 thyroid cell line were compared by quantitative RT-PCR and flow cytometry using interferon-γ and zinc as stimuli. MT were clearly overexpressed in nine of 14 GD glands. MT expression distribution in GD was almost reciprocal to that of HLA class II. In vitro analysis of MT and HLA class II demonstrated that MT is induced more slowly and at a lower level than HLA. Moreover, the main MT inducer, zinc, reduces interferon-γ-induced class II expression. These findings show that MT and HLA class II play very different roles in the autoimmune process by affecting the thyroid gland, thereby pointing to the possible role of MT as a marker of cell stress and homeostasis restoration in GD.
    The Journal of clinical endocrinology and metabolism 11/2011; 97(2):446-54. · 6.50 Impact Factor
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    ABSTRACT: T-cell tolerance to self-antigens is established in the thymus through the recognition by developing thymocytes of self-peptide-MHC complexes and induced and maintained in the periphery. Efficient negative selection of auto-reactive T cells in the thymus is dependent on the in situ expression of both ubiquitous and tissue-restricted self-antigens and on the presentation of derived peptides. Weak or inadequate intrathymic expression of self-antigens increases the risk to generate an autoimmune-prone T-cell repertoire. Indeed, even small changes of self-antigen expression in the thymus affect negative selection and increase the predisposition to autoimmunity. Together with other mechanisms, tolerance is maintained in the peripheral lymphoid organs via the recognition by mature T cells of a similar set of self-peptides in homeostatic conditions. However, non-lymphoid peripheral tissue, where organ-specific autoimmunity takes place, often have differential functional processes that may lead to the generation of epitopes that are absent or non-presented in the thymus. These putative differences between peptides presented by MHC molecules in the thymus and in peripheral tissues might be a major key to the initiation and maintenance of autoimmune conditions.
    Frontiers in Immunology 01/2013; 4:442.
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    10/2011; , ISBN: 978-953-307-643-0


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May 19, 2014