Development Of Spontaneous Autoimmune Thyroiditis Research Articles

A study of programmed death-1/programmed death ligand and iodine-induced autoimmune thyroiditis in NOD.H-2h4 mice.

Excess iodine will trigger the occurrence of autoimmune thyroiditis (AIT), and programmed death-1 (PD-1)/programmed death ligand (PD-L) will also contribute to the development of AIT. The purpose of this study was to explore the role that negative regulatory signals mediated by PD-1/PD-L play in the development of spontaneous autoimmune thyroiditis (SAT) in NOD.H-2h4 mice when they are exposed to iodine. Programmed death ligand 1 (PD-L1) antibody was administered intraperitoneally to NOD.H-2h4 mice. The relevant indicators were determined by flow cytometry, real-time quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, immunohistochemistry, pathological hematoxylin and eosin staining, and arsenic-cerium catalytic spectrophotometry. Results showed that the level of urinary iodine, the level of thyroid lymphocyte infiltration, the level of thyroglobulin antibodies (TgAb) and interferon (IFN-γ)/tumor necrosis factor (TNF-α)/interleukin (IL-2)/IL-17, and the relative expression of PD-1/PD-L1/programmed death-2 (PD-L2) increased with the intervention of excess iodine. After the intervention of the PD-L1 antibody, the expression of PD-1/PD-L1/PD-L2 in different degrees was inhibited, but the level of thyroid lymphocyte infiltration and serum TgAb/IFN-γ/TNF-α/ IL-2/IL-17 did not decrease. Collectively, although PD-1/PD-L participates in the occurrence of SAT and induces inflammation, administration of the PD-L1 antibody does not effectively improve the pathological process of SAT. More research is needed to determine whether PD-1/PD-L intervention can treat autoimmune thyroid disease.

Mechanisms by Which B Cells and Regulatory T Cells Influence Development of Murine Organ-Specific Autoimmune Diseases.

Experiments with B cell-deficient (B−/−) mice indicate that a number of autoimmune diseases require B cells in addition to T cells for their development. Using B−/− Non-obese diabetic (NOD) and NOD.H-2h4 mice, we demonstrated that development of spontaneous autoimmune thyroiditis (SAT), Sjogren’s syndrome and diabetes do not develop in B−/− mice, whereas all three diseases develop in B cell-positive wild-type (WT) mice. B cells are required early in life, since reconstitution of adult mice with B cells or autoantibodies did not restore their ability to develop disease. B cells function as important antigen presenting cells (APC) to initiate activation of autoreactive CD4+ effector T cells. If B cells are absent or greatly reduced in number, other APC will present the antigen, such that Treg are preferentially activated and effector T cells are not activated. In these situations, B−/− or B cell-depleted mice develop the autoimmune disease when T regulatory cells (Treg) are transiently depleted. This review focuses on how B cells influence Treg activation and function, and briefly considers factors that influence the effectiveness of B cell depletion for treatment of autoimmune diseases.

Follicular B Cells in Thyroids of Mice with Spontaneous Autoimmune Thyroiditis Contribute to Disease Pathogenesis and Are Targets of Anti-CD20 Antibody Therapy

B cells are required for development of spontaneous autoimmune thyroiditis (SAT) in NOD.H-2h4 mice where they function as important APCs for activation of CD4(+) T cells. Depletion of B cells using anti-CD20 effectively inhibits SAT development. The goals of this study were to characterize the B cells that migrate to thyroids in SAT, and to determine whether anti-CD20 effectively targets those B cells in mice with established SAT. The results showed that most thyroid-infiltrating B cells in mice with SAT are follicular (FO) B cells. Expression of CD80, CD86, and CD40 was significantly increased on FO, but not marginal zone, splenic B cells after SAT development. Thyroid-infiltrating and peripheral blood B cells had lower expresion of CD20 and CD24 compared with splenic and lymph node FO B cells. Despite reduced CD20 expression, anti-CD20 depleted most B cells in thyroids of mice with established SAT within 3 d. B cell depletion in thyroids of mice given anti-CD20 was more complete and longer lasting than in spleen and lymph nodes and was comparable to that in blood. Circulation of B cells was required for effective and rapid removal of B cells in thyroids because preventing lymphocyte egress by administration of FTY720 abrogated the effects of anti-CD20 on thyroid B cells. Therefore, the FO subset of B cells preferentially contributes to SAT development and persistence, and anti-CD20 targeting of FO B cells effectively eliminates B cells in the target organ even though thyroid B cells have decreased CD20 expression.

Follicular B cells, not Marginal zone B cells, preferentially contribute to development of spontaneous autoimmune thyroiditis (SAT) and are targets of anti-CD20 therapy (56.12)

Abstract SAT in NOD.H-2h4 mice is a chronic organ-specific autoimmune disease characterized by mononuclear cell infiltration of the thyroid and destruction of thyroid follicles by infiltrating inflammatory cells. Like other autoimmune diseases, B cells play a critical role in pathogenesis of SAT as important antigen presenting cells (APCs) for activation of CD4+ T cells. However it is not yet known which subsets of B cells are important for SAT development. In this study, we found that expression of the co-stimulatory molecules CD80 and CD86 was significantly increased on splenic CD23hiCD21low follicular (FO) B cells, but not marginal zone (MZ) B cells, after SAT development, but absolute numbers and percentages of splenic FO B cells were not altered. In draining lymph nodes, CD40 expression on FO B cells was also increased in mice with SAT. All thyroid infiltrating B cells in mice with SAT were FO B cells. Depletion of FO B cells by anti-CD20 antibody ameliorated established SAT, and anti-thyroglobulin antibody levels were reduced. Moreover, administering anti-CD20 to mice with established SAT results in depletion of B cells in the thyroid and depletion of thyroid B cells is longer lasting than depletion of splenic B cells. On the basis of these findings, we suggest the FO subset of B cells preferentially contributes to SAT development and persistence, and targeting FO B cells after disease develops provides an effective means to treat autoimmune diseases.

Effects of depletion of CD4+FoxP3+ Treg on development of spontaneous autoimmune thyroiditis (SAT) in WT and B cell deficient (B-/-) NOD.H-2h4 mice (123.10)

Abstract NOD.H-2h4 mice given NaI in their water develop SAT with chronic inflammation of the thyroid by T and B cells. B-/- mice are resistant to SAT, but develop SAT after transient depletion of Treg by anti-CD25. However, NOD.H-2h4 mice have significant numbers of CD4+FoxP3+ Treg that are CD25-. Generation of mice expressing the human diphtheria toxin receptor (DTR) under control of the FoxP3 promoter allows for selective depletion of Foxp3+ cells by diphtheria toxin (DT). Anti-CD25 depletion of Treg lasts 3-4 weeks, whereas most Treg return 4-5 days after DT treatment. In WT and B-/- FoxP3-DTR NOD.H-2h4 mice, injection of DT eliminates essentially all Treg in blood and spleen within 2 days. As with anti-CD25 depletion, DT treatment allows for SAT development in B-/- mice even though Treg are depleted for only a few days, and SAT in DT-treated WT mice is slightly increased. We established a transfer model in which splenocytes from CD28-/-B-/- mice (effector cells) were cultured with or without sorted Treg from FoxP3-DTR WT or B-/- mice. After transfer to TCRα-/- mice, recipients of Treg from B-/- mice developed significantly less severe SAT than did mice receiving Treg from WT mice. As there is no source of new FoxP3-DTR Treg, DT treatment 2 days after transfer to recipient mice resulted in permanent depletion of Treg. This abrogated the suppression, suggesting that suppression of SAT requires continued inhibition of effectors by Treg during disease development.

B Cell Depletion Inhibits Spontaneous Autoimmune Thyroiditis in NOD.H-2h4 Mice

B cells are important for the development of most autoimmune diseases. B cell depletion immunotherapy has emerged as an effective treatment for several human autoimmune diseases, although it is unclear whether B cells are necessary for disease induction, autoantibody production, or disease progression. To address the role of B cells in a murine model of spontaneous autoimmune thyroiditis (SAT), B cells were depleted from adult NOD.H-2h4 mice using anti-mouse CD20 mAb. Anti-CD20 depleted most B cells in peripheral blood and cervical lymph nodes and 50-80% of splenic B cells. Flow cytometry analysis showed that marginal zone B cells in the spleen were relatively resistant to depletion by anti-CD20, whereas most follicular and transitional (T2) B cells were depleted after anti-CD20 treatment. When anti-CD20 was administered before development of SAT, development of SAT and anti-mouse thyroglobulin autoantibody responses were reduced. Anti-CD20 also reduced SAT severity and inhibited further increases in anti-mouse thyroglobulin autoantibodies when administered to mice that already had autoantibodies and thyroid inflammation. The results suggest that B cells are necessary for initiation as well as progression or maintenance of SAT in NOD.H-2h4 mice.

B cell-deficient NOD.H-2h4 mice have CD4+CD25+ T regulatory cells that inhibit the development of spontaneous autoimmune thyroiditis.

Wild-type (WT) NOD.H-2h4 mice develop spontaneous autoimmune thyroiditis (SAT) when given 0.05% NaI in their drinking water, whereas B cell–deficient NOD.H-2h4 mice are SAT resistant. To test the hypothesis that resistance of B cell–deficient mice to SAT was due to the activity of regulatory CD4+CD25+ T (T reg) cells activated if autoantigen was initially presented on non–B cells, CD25+ T reg cells were transiently depleted in vivo using anti-CD25. B cell–deficient NOD.H-2h4 mice given three weekly injections of anti-CD25 developed SAT 8 wk after NaI water. Thyroid lesions were similar to those in WT mice except there were no B cells in thyroid infiltrates. WT and B cell–deficient mice had similar numbers of CD4+CD25+Foxp3+ cells. Mice with transgenic nitrophenyl-specific B cells unable to secrete immunoglobulin were also resistant to SAT, and transient depletion of T reg cells resulted in severe SAT with both T and B cells in thyroid infiltrates. T reg cells that inhibit SAT were eliminated by day 3 thymectomy, indicating they belong to the subset of naturally occurring T reg cells. However, T reg cell depletion did not increase SAT severity in WT mice, suggesting that T reg cells may be nonfunctional when effector T cells are activated; i.e., by autoantigen-presenting B cells.

High incidence of spontaneous autoimmune thyroiditis in immunocompetent self-reactive human T cell receptor transgenic mice

Autoantigen-specific TCR transgenic mice allow us to assess the role of T cells in autoimmunity. We have recently generated humanized TAZ10 transgenic mice expressing the human TCR specific for the immunodominant epitope of thyroid peroxidase (TPO). We have shown that these transgenic mice do not undergo tolerance in vivo and that on Rag deficient background they are susceptible to spontaneous autoimmune thyroiditis. Here we show that, in contrast to other transgenic models of autoimmunity, almost all TCR + Rag1 + (T+R+) T cells are activated in vivo leading to the development of spontaneous autoimmune thyroiditis. In these mice, disease is also accompanied by a significant reduction of CD4+CD25 hi regulatory T cells. These data indicate that the pathogenic activity of the self-reactive TCR can circumvent the regulatory function operated by the non-transgenic T cells that are normally present in T+R+ mice, leading to autoimmunity.

Role of TGFbeta in development of spontaneous autoimmune thyroiditis in NOD.H-2h4 mice.

Nearly 100% of NOD.H-2h4 mice develop spontaneous autoimmune thyroiditis (SAT) and produce anti-mouse thyroglobulin autoantibodies when they receive 0.05% NaI in their drinking water beginning at 8 wk of age. Our previous studies showed that TGFbeta1 mRNA was constitutively expressed in thyroids and spleens of normal NOD.H-2h4 mice but not other strains of mice. To determine whether TGFbeta might have a role in SAT, mice were given anti-TGFbeta mAb at various times during development of SAT. Anti-TGFbeta markedly inhibited development of SAT and production of anti-mouse thyroglobulin IgG1 autoantibodies. Anti-TGFbeta was most effective in inhibiting SAT when given during the time thyroid lesions were developing, i.e., starting 4 wk after administration of NaI water. The active form of the TGFbeta1 protein was present in thyroids of mice with SAT but not in normal NOD.H-2h4 thyroids. However, thyrocytes of normal NOD.H-2h4 thyroids did express latent TGFbeta1. TGFbeta1 protein expression in the thyroid correlated with SAT severity scores, and administration of anti-TGFbeta inhibited TGFbeta1 protein expression in both the thyroid and spleen. TGFbeta1 was produced primarily by inflammatory cells and was primarily localized in areas of the thyroid containing clusters of CD4(+) T and B cells. Depletion of CD8(+) T cells had no effect on TGFbeta1 protein expression. Activation of splenic T cells was apparently not inhibited by anti-TGFbeta, because up-regulation of mRNA for cytokines and other T cell activation markers was similar for control and anti-TGFbeta-treated mice. TGFbeta1 may function by promoting migration to, or retention of, inflammatory cells in the thyroid.

Characteristics of Inflammatory Cells in Spontaneous Autoimmune Thyroiditis of NOD.H-2h4 Mice

Thyroid lesions develop in most NOD.H-2h4 mice 6 weeks after they are given 0.05% NaI in drinking water. B cells are required for spontaneous autoimmune thyroiditis (SAT) development, and anti-thyroglobulin autoantibody levels correlate with SAT severity. Immunohistochemical staining of thyroids obtained 2–10 weeks after administration of NaI water suggested that CD4+ T cells initially infiltrated the thryoid, followed by CD8+ T cells and B cells. Intrathyroidal CD4+ T cells are more numerous than CD8+ T cells. CD4+ T cells and B cells form aggregates in the thyroid, while CD8+ T cells are scattered throughout the thyroid. Intrathyroidal germinal centre-like structures could be observed in thyroid lesions with 2–3+ SAT and intrathyroidal B cells co-expressed OX40L. By RT–PCR, intrathyroidal expression of OX40L, OX40, CD40L, IL-2R, CTLA-4 and Igβ mRNA correlated closely with the SAT severity score. These molecules were not expressed in normal thyroids. In the spleen, OX40L-positive cells were detected at 2 weeks and increased 4–6 weeks after NaI water. OX40, OX40L, CD40L, IL-2R and B7-1 as well as IFN-γ and IL-4 mRNA were minimally expressed in normal spleens, usually began to be expressed at 2 weeks and increased to maximal level 4–8 weeks after NaI water. These results suggest that in NOD.H-2h4 mice, the OX40L, OX40, CD40L and B7 molecules, which increase in the spleen and thyroid of these mice after receiving NaI water, may play a role in SAT development, implying that one or more of these molecules might be good targets for the prevention or treatment of SAT.

Early requirement for B cells for development of spontaneous autoimmune thyroiditis in NOD.H-2h4 mice.

B cells are known to play an important role in the pathogenesis of several autoimmune diseases. NOD.H-2h4 mice develop spontaneous autoimmune thyroiditis (SAT) and anti-mouse thyroglobulin (MTg) autoantibodies, the levels of which correlate closely with the severity of thyroid lesions. NOD.H-2h4 mice genetically deficient in B cells (NOD.Kmu(null)) or rendered B cell-deficient by treatment from birth with anti-IgM develop minimal SAT. B cells were required some time in the first 4-6 wk after birth, because NOD.Kmu(null) or NOD.H-2h4 mice did not develop SAT when they were reconstituted with B cells as adults. The requirement for B cells was apparently not solely to produce anti-MTg autoantibodies, because passive transfer of anti-MTg Ab did not enable B cell-deficient mice to develop SAT, and mice given B cells as adults produced autoantibodies but did not develop SAT. B cell-deficient mice developed SAT if their T cells developed from bone marrow precursors in the presence of B cells. Because B cells are required early in life and their function cannot be replaced by anti-MTg autoantibodies, B cells may be required for the activation or selection of autoreactive T cells. These autoreactive T cells are apparently unable to respond to Ag if B cells are absent in the first 4-6 wk after birth.

Inhibition of the Development of Spontaneous Autoimmune Thyroiditis in the Obese Strain (OS) Chickens byIn VivoTreatment With Anti-CD4 or Anti-CD8 Antibodies

The involvement of CD4+and CD8+T cells in pathogenesis of spontaneous autoimmune thyroiditis (SAT) in obese strain (OS) chickens has not been studied in depth until now. We depleted CD4+or CD8+T cells in OS chickens by treatment with murine monoclonal anti-CD4 or anti-CD8 antibodies at 3 day intervals beginning at hatching. The birds were killed at 19–25 days of age. Treatment with anti-CD4 antibody completely prevented SAT development, while treatment with anti-CD8 antibody partially inhibited SAT. These results show the critical role of CD4+T cells in the development of SAT in OS chickens, and indicate that CD8+T cells are also involved in SAT pathogenesis.

Development of spontaneous autoimmune thyroiditis in Obese strain (OS) chickens.

Chickens of the Obese strain (OS) are known to develop spontaneous autoimmune thyroiditis (SAT) in the first 2-3 weeks post-hatching, but onset and severity of SAT for this period among sublines of OS chickens has not yet been analysed in detail. In the present paper, we described the kinetics of SAT in age-matched OSB13B13C, OSB5B5C, OSB15B15INN and OSB5B5INN chicken sublines. The results revealed no thyroid infiltration in OS fetuses at 20th ED of the analysed sublines. Mononuclear cell infiltration of thyroid was first noted in 2-4-day-old chickens, followed by aggravation of thyroiditis in 4-week-old OSB13B13C and OSB15B15INN chickens and in 5-week-old OSB5B5C birds. Interestingly, two subpopulations of OSB5B5INN chickens were found with different kinetics of SAT development: one with degree of SAT lower than 40%, was designated "low responders" and the other, with similar degrees of SAT as the other three sublines, was characterized as "high responders". Our results allow an age-dependent prediction of SAT development among OS chickens and the rational design of animal experiments, particularly for assessing the relevance of therapeutic interventions.

Effect of growth hormone and thyroid hormone on autoimmune thyroiditis in obese chickens

The effect of thyroxine (T 4) and recombinant (rcGH) or purified pituitary-derived (pcGH) chicken growth hormone on the development of spontaneous autoimmune thyroiditis (SAT) was examined in the Obese strain (OS) chicken. Day-old OS chicks were randomly assigned to a control or 1.0 ppm T 4 supplemented diet and a vehicle or 500 μg rcGH/kg BW daily injection, using a 2×2 factorial design. At 4 weeks, sera were analyzed for anti-thyroglobulin autoantibody (TgAAb) using a kinetics-based ELISA. Leucocytic infiltration of the thyroid was assessed using computer-based video imaging techniques. A close correlation between TgAAb and thyroid infiltration was seen with both being decreased ( p<0.05) by the T 4/rcGH treatment. Neither the T 4 or rcGH alone produced this effect and the rcGH treatment significantly elevated TgAAb. In a second experiment, all but the control group received 1.0 ppm T 4 supplementation and two of the T 4-treated groups received either 50 or 200 μg pcGH/kg BW by daily injection. As before, T 4/pcGH significantly reduced TgAAb and thyroid infiltration. T 4 alone produced no significant effects. These data support the conclusion that the combined treatment of T 4 and cGH exert an immunomodulatory effect within a strain that is predisposed to autoimmune thyroiditis while GH treatment alone exacerbated the condition. These results also show that video imaging techniques can be used to evaluate the extent of histopathology present within the OS thyroid.

Disturbed immuno-endocrine communication via the hypothalamo-pituitary-adrenal axis in autoimmune disease.

Previous studies in our laboratory demonstrated an altered immuno-endocrine feedback communication via the hypothalamo-pituitary-adrenal (HPA) axis, which may be an important modulatory factor in the development of spontaneous autoimmune thyroiditis in Obese strain (OS) chickens. These birds show a significantly lower, or even absent, increase in serum glucocorticoid levels in response to an intravenous injection of antigen or conditioned medium (CM) from mitogen-stimulated spleen cells known to contain glucocorticoid-increasing factors (GIFs), notably interleukin-1 (IL-1). The present study was aimed at investigating this feedback regulation in animal models with spontaneous systemic autoimmune diseases, such as the UCD-200 chicken, which serves as a model for human scleroderma, and various murine lupus models. In contrast to OS chickens, UCD-200 chickens displayed a nearly normal plasma corticosterone surge in response to CM, and IL-1 was again identified as the primary GIF in CM. Recombinant IL-1 also induced a drastic increase in plasma corticosterone levels in various strains of normal mice. A similar increase was observed in the bacterial lipopolysaccharide-resistant C3H/HeJ strain, thus excluding the possibility of bacterial endotoxin contamination. However, in young lupus-prone (NZB/W)F1 and MRL/MP-lpr mice, a significantly lower increase in plasma corticosterone levels was observed after injection of recombinant IL-1, suggesting a deficient immuno-endocrine communication via the HPA loop in this instance as well. Detailed studies to identify further cytokines with GIF activity in the avian and murine systems showed that both IL-6 and tumor necrosis factor-alpha could induce increased plasma corticosterone levels in mice, but not in chickens. IL-3, IL-8, transforming growth factor-beta, interferon-gamma and granulocyte-macrophage colony-stimulating factor were devoid of GIF activity in both chickens and mice.

The role of genetically-determined primary alterations of the target organ in the development of spontaneous autoimmune thyroiditis in obese strain (OS) chickens.

Immunologists working in the field of autoimmunity tend to concentrate all their efforts on the elucidation of possible malfunctions of the immune system, particularly pathologic changes of immune regulation. Also in the OS model various groups of investigators emphasized this approach, although it was already clear early in the history of this model that SAT has a multigenic background. The fact that this disease cannot be transferred into normal, histocompatible animals without an appropriate non-MHC linked genetic background was a strong indication that detailed studies of thyroid-associated factors may be warranted for the elucidation of the pathogenesis of this disease and perhaps also its human counterpart, Hashimoto thyroiditis. Since several reviews on the immunologic aspects in the OS model have been published in recent years we have in this communication attempted to discuss the - mostly still rudimentary - findings concerning the target organ itself, including morphological changes before the beginning of infiltration, the analysis of Tg, the altered thyroid function before onset of SAT, the results of cross-breeding studies of OS and inbred normal chickens in respect to the susceptibility of the offspring for the transfer of SAT, the possible role of a virus infection and the aberrant expression of MHC class II antigens on TEC. Cross-breeding studies revealed that most probably a single gene is responsible for the primary altered thyroid function and at least 3 genes code for the susceptibility of the OS thyroid gland to the autoimmune attack. It is not yet clear for which of the above-mentioned observations each of these genes is responsible and what is/are the initial triggering mechanism(s). Ongoing studies in our laboratory concentrate on this question, specifically the potential role of endogenous viruses in this process.

Elevation of corticosteroid-binding globulin in obese strain (OS) chickens: possible implications for the disturbed immunoregulation and the development of spontaneous autoimmune thyroiditis.

Basal plasma levels of corticosterone and corticosteroid-binding globulin (CBG) have been investigated in Obese strain (OS) chickens afflicted with spontaneous autoimmune thyroiditis (SAT). Corticosterone was determined radioimmunologically, and CBG by using a highly sensitive radioligand saturation assay. OS chickens displayed total corticosterone levels not different from healthy normal White Leghorn (NWL) chickens. CBG, however, was found to be twice as high in OS chickens as compared with their healthy counterparts, irrespective of sex or age. This quantitative difference in the CBG level is not compensated for by either altered affinity or specificity of the molecule. Furthermore, no differences were found in the response of OS and NWL lymphocytes to the suppressive effect of glucocorticoids in vitro. We therefore assume that OS animals are deficient in free, hormonally active corticosterone. An additional indication for such a diminished glucocorticoid tonus was that in vivo treatment of OS chickens with glucocorticoid hormones, thus increasing the free and active hormone fraction, normalizes the T cell hyperreactivity and significantly reduces thyroid infiltration. Possible pathophysiological implications of a diminished glucocorticoid tonus for spontaneous autoimmunity, as well as possible explanations for the beneficial effects of glucocorticoid treatment on the development of SAT, are discussed.

Genetic background of spontaneous autoimmune thyroiditis in the obese strain of chickens studied in hybrids with an inbred line.

To determine the number and function of genes which are responsible for spontaneous autoimmune thyroiditis (SAT) in the obese strain (OS) of chickens we crossed birds of this strain (B15/B15) with those of the inbred CB line (B12/B12). The progeny was analyzed for autoantibodies to thyroglobulin (TgAAb) and for histopathological changes in the thyroid glands. In F1 (OS X CB) hybrids only those animals which derived from CB mothers had circulating TgAAb, the progeny from the reverse combination female OS X male CB was negative. Since the disease is not inherited by OS males only, we conclude that maternal TgAAb, which are transferred from the egg yolk to the embryo, might prevent the immune system of the F1 chickens from TgAAb formation via blocking or eliminating the respective antigens. Those F1 hybrids which have high TgAAb levels in the serum show only little or no thyroiditis. Together with other observations, these data lead to the conclusion that the thyroid gland of the F1 hybrids is not susceptible to TgAAb. This supports previous findings that a genetically determined thyroid abnormality is a prerequisite for the full development of SAT. The low degree of SAT in backcross (F1 X OS) animals and F2 hybrids suggests that several genes are involved in the disease. MHC typing of these generations revealed that the B haplotype affects the time of SAT onset.

Distribution and functional analysis of B-L/Ia-positive cells in the chicken: Expression of B-L/Ia antigens on thyroid epithelial cells in spontaneous autoimmune thyroiditis

The B-L region of the chicken major histocompatibility complex (MHC), the so-called B-locus, corresponds to the murine H-2 I-region. Using alloantibodies and monoclonal antibodies to B-L we analyzed: (a) the tissue distribution of B-L + cells, (b) the function of B-L + cells, and (c) the possible role of B-L + cells in the development of spontaneous autoimmune thyroiditis (SAT) in Obese strain (OS) chickens. The tissue distribution of B-L + cells in peripheral blood and various lymphoid and nonlymphoid organs corresponds to what is known for mammals. In the bursa of Fabricius most lymphoid cells and the dendritic cells carry the B-L antigen; B-L + thymic nurse cells (TNC) first appear on day 17 of embryonic life; chickens possess dendritic B-L + cells in the skin resembling mammlian Langerhans cells; in addition we found that the microglia is unequivocally B-L +. B-L + peripheral blood lymphocytes (PBL) were separated with a fluorescence-activated cell sorter. Ten percent of unstimulated PBL and 60% of phytohemagglutinin (PHA) stimulated T-cell blasts are B-L +. In graft-vs-host (GvH) assays B-L − cells were identified as the effector cells. These cells respond to PHA and concanavalin A (Con A), but not to pokeweed mitogen (PWM). B-L + cells cannot be stimulated by Con A and PHA, but respond to PWM. They possess only a very low activity in GvH assays which can be inhibited by anti-T-cell sera. In OS chickens B-L +/non-B/, non-T and B-L + T (blasts?) cells are found in the “first line” of mononuclear cell infiltration in the thyroid glands. Most interesting, thyroid epithelial cells—which are normally B-L −—become B-L + in the neighbourhood of B-L + infiltrating mononuclear cells. This observation may be of significance for autoantigen presentation and perpetuation in autoimmune thyroiditis. Finally, OS thymuses contain significantly less TNC than normal controls.

Immunofluorescence studies on the codistribution immune deposits and complement in the thyroid glands of obese strain (OS) chickens

This study demonstrates immune complexes in thyroid glands of Obese strain (OS) chickens, that consist of thyroglobulin (Tg) and antibodies to Tg. In IIF tests it was shown that these complexes fix complement with an age-dependent increase from 12 % in 19-day-old embryos up to 100 % in 6-week-old animals. This finding and the observation that the deposition of complement-binding immune complexes precede cellular infiltration of the thyroid gland and correlate with the serum titer of Tg-Ab (as one parameter of the disease) points towards a role as one initial effector mechanism for the development of spontaneous autoimmune thyroiditis (SAT).