Thyroglobulin-treated blood dendritic cells induce IgG anti-thyroglobulin antibody in vitro in Hashimoto's thyroiditis

Modulation of Dendritic Cell Function and Cytokine Production to Prevent Thyroid Autoimmunity

Understanding autoimmune thyroid diseases provides an unique perspective on the role of various components of the immune system in the pathogenesis of organ specific autoimmune diseases, whether the effector mechanism involves autoantibodies or T cells. Hashimoto's thyroiditis (HT) is largely mediated by thyroglobulin specific T cells, while Graves' disease (GD) is mediated by thyrotropin receptor specific autoantibodies. HT is characterized by thyroid destruction mediated by infiltrating or activated resident immune cells through a variety of mechanisms. In contrast GD is characterized by excessive production of thyroid hormone with little or no glandular destruction. Irrespective of the effector mechanism involved, dendritic cells (DCs) are required for the induction of an efficient primary response and thus are the first cells involved in an autoimmune response. DCs also provide the essential link between the innate and the adaptive immune system through co-stimulatory molecules and the production of cytokines and chemokines. Furthermore, inflammatory cytokines also appear to enhance the susceptibility of thyrocytes to apoptosis. In this review, we discuss the role of innate immunity in initiating an adaptive autoimmune response against the thyroid. We will explore the role of different mechanisms involved in breaking self-tolerance to thyroid antigens. Further, we will discuss recent developments in the development of experimental therapeutics against AITD.

Cancer immunotherapy using dendritic/tumour-fusion vaccine induces elevation of serum anti-nuclear antibody with better clinical responses

Dendritic cell (DC) vaccines might induce both anti-tumour immunity and autoimmunity. In this report, we demonstrate elevated levels of anti-nuclear antibody (ANA) in the sera of patients with cancer who had received immunotherapy with a dendritic/tumour-fusion vaccine. Twenty-two patients were treated with DC vaccine of fusion cells composed of autologous DCs and tumour cells (DC/tumour-fusion vaccine), which was generated by treating each cell type with polyethylene glycol. Nine of the 22 patients were treated with both the DC/tumour-fusion vaccine and systemic administration of recombinant human interleukin (rhIL)-12. Serum levels of ANA were examined with an enzyme-linked immunosorbent assay kit. One patient with gastric carcinoma (patient 1, DC/tumour-fusion vaccine alone), one patient with breast cancer (patient 2, DC/tumour-fusion vaccine alone) and one patient with ovarian cancer (patient 3, DC/tumour-fusion vaccine + rhIL-12) showed significant elevations of serum ANA levels during treatment. In patient 1 malignant ascitic effusion resolved and serum levels of tumour markers decreased. Patients 2 and 3 remained in good physical condition during treatment for 24 and 9 months, respectively. Immunoblot analysis indicated antibody responses to autologous tumour cells after vaccination in patient 2. None of the treated patients showed clinical symptoms suggesting autoimmune disease. Patients with elevated serum levels of ANA had significantly longer treatment periods than those without it. Elevated serum levels of ANA after DC/tumour-fusion cell vaccine might be associated with anti-tumour immune response induced by the vaccination.

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.

Interactions between the mannose receptor and thyroid autoantigens

Thyroid autoantigens require internalization and processing by antigen-presenting cells to induce immune responses. Besides pinocytosis, antigen uptake can be receptor-mediated. The mannose receptor (ManR) has a cysteine rich domain (CR) and eight carbohydrate recognition domains (CRD) that bind glycosylated proteins. The TSH receptor (TSHR), thyroid peroxidase (TPO) and thyroglobulin (Tg) are glycoproteins. To investigate a role for the ManR in thyroid autoimmunity, we tested the interaction between these autoantigens and chimeric ManRs. Plasmids encoding the CR-domain linked to IgG-Fc (CR-Fc) and CDR domains 4-7 linked to IgG-Fc (CDR4-7-Fc) were expressed and purified with Protein A. Enzyme-linked immunosorbent assay (ELISA) plates were coated with human thyroid autoantigens and CR-Fc or CRD4-7-Fc binding detected with peroxidase-conjugated anti-IgG-Fc. CRD4-7-Fc binding was highest for the TSHR, followed by Tg and was minimal for TPO. CR-Fc bound to Tg but not to TSHR or TPO. The interaction between the TSHR and CRD-Fc was calcium-dependent; it was inhibited by mannose (not galactose), and required a glycosylated TSHR A-subunit. Moreover, precomplexing the TSHR A-subunit with CRD-Fc (but not CR-Fc), or adding mannose (but not galactose), decreased in vitro responses of splenocytes from TSHR-immunized mice. Our data indicate that the ManR may participate in autoimmune responses to Tg and the TSHR but not to TPO. Most important, ManR binding of heavily glycosylated TSHR A-subunits suggests a mechanism by which the minute amounts of A-subunit protein shed from the thyroid may be captured by antigen-presenting cells located in the gland or in draining lymph nodes.

Transfer of dendritic cells (DC) ex vivo stimulated with interferon-gamma (IFN-gamma) down-modulates autoimmune diabetes in non-obese diabetic (NOD) mice

The NOD mouse has been used to explore the many features of insulin-dependent diabetes mellitus (IDDM) that is caused by the destruction of insulin-producing beta cells in the islets of Langerhans of the pancreas. Self-reactive T cells have been considered to mediate IDDM in the NOD mouse, and antigen-presenting cells like DC and macrophages are expected to be involved in the processes from their role in generating regulatory or effector T cells. The present study shows that transfer of IFN-gamma-stimulated DC of the NOD or ICR mouse into the NOD mouse did not accelerate IDDM onset but afforded long-lasting protection against clinical and histological signs of IDDM in the recipient mice. The anti-diabetogenic ability was unique to IFN-gamma-stimulated DC when compared with unstimulated DC. A considerable proportion of the injected IFN-gamma-stimulated DC was demonstrated to migrate into the pancreas and its associated lymphoid tissues, suggesting the DC exert their anti-diabetogenic effects there. These findings suggest that development of autoimmune diabetes in the NOD mouse is under the control of DC, and that IDDM onset could be controlled by appropriately manipulating DC systems in vivo, which may open the gate for the therapeutic application of ex vivo-conditioned DC to human IDDM.

Prevention of diabetes in nonobese diabetic mice by dendritic cell transfer

The purpose of this study was to determine the effect of dendritic cell (DC) transfers on the incidence of diabetes in female nonobese diabetic (NOD) mice. Groups of 4-wk-old NOD female mice were given a single foot pad of DCs (70-90% purity) isolated from the draining lymph nodes (LN) of the pancreas (PLN), the cervical LNs, or the axillary/inguinal LNs. In addition, other groups of NOD mice received purified spleen DCs, purified PLN T cells (the major contaminating population in DC preparations), or the injection vehicle PBS. All groups were monitored for diabetes for one year. Significant protection from diabetes was observed in NOD mice receiving greater than 1 x 10(4) PLN DCs in comparison to mice receiving other DCs populations, PLN T cells, or PBS (P less than 0.05). The pancreata of NOD mice that received PLN DCs demonstrated significantly lower levels of lymphocytic infiltration in the islets that age-sex matched nondiabetic female NOD control mice (P less than 0.05). LN cells from nondiabetic NOD mice that received PLN DC protected irradiated female recipients from the adoptive transfer of diabetes to a greater degree than LN cells from age and sex matched nondiabetic female NOD mice that did not receive PLN DC transfers at 36 d (P = 0.014) and at 1 yr (P = 0.0015) after transfer. These data suggest that the PLN DC transfers are able to modulate autoimmunity and limit diabetes expression in the NOD mouse. PLN DCs transfers may regulate autoimmunity by the induction of regulatory cells.

Thyroid autoantigens and human T cell responses

We investigated the ability of T cells from patients with Hashimoto's thyroiditis and with Graves' disease as well as control donors to proliferate in response to thyroid peroxidase (TPO) and thyroglobulin using (i) lymphoid cells from different lymphoid organs; (ii) unfractionated or CD8- depleted lymphoid suspensions or T cells + autologous low density cells (LDC); (iii) 200-microliters well cultures and 20-microliters hanging-drop microcultures; and (iv) intact TPO and thyroglobulin, denatured thyroglobulin and 12 synthetic peptides predicted on the basis of the amino acid sequence of TPO to be T cell epitopes. In 200-microliters well cultures, proliferative responses (assessed in terms of 3H-thymidine uptake) to intact TPO or thyroglobulin, digested thyroglobulin or synthetic TPO peptides were not significantly different in unfractionated or CD8-depleted lymphoid suspensions from blood, thyroid or lymph nodes of TPO/thyroglobulin autoantibody-positive patients, autoantibody-negative patients or control donors. In contrast, blood T cells from some high titre patients with Hashimoto's thyroiditis (but not from healthy individuals) proliferated in response to intact thyroglobulin or TPO presented by autologous LDC in hanging-drop microcultures. Heat denatured thyroglobulin (with which thyroglobulin autoantibodies do not interact) did not stimulate proliferation and this observation, together with the ability of T cells from some patients to respond to intact thyroglobulin in the absence of LDC, indicated that thyroglobulin-specific B cells may be involved in antigen presentation. As we were unable to demonstrate proliferation by blood T cells + LDC from all thyroglobulin antibody-positive patients with Hashimoto's thyroiditis, our studies suggest that the presence of sufficient precursor T cells, as well as the number and type of antigen-presenting cells, are critical for T cell proliferative responses to human TPO and thyroglobulin.

Autoantibody specific for a thyroglobulin epitope inducing experimental autoimmune thyroiditis or its anti-idiotype correlates with the disease

In order to elucidate the role of anti-thyroglobulin (Tg) autoantibodies (A-Ab) in experimental autoimmune thyroiditis (EAT), a kinetic study was conducted in EAT-susceptible (CBA/J) and non-susceptible (C57BL/6) strains of mice. From day 0 to 70 post-Tg immunization, titers of A-Ab to Tg and to the linear 5-10-kDa Tg tryptic fragment inducing EAT as well as anti-idiotypic A-Ab representing the internal image of the thyroidogeneic antigen were measured. EAT onset, development and recovery correlate with the presence of two subsets of A-Ab only in susceptible strains of mice. First, with the presence of anti-Tg A-Ab to one determinant borne by the linear 5-10-kDa Tg tryptic fragment, and second with the presence of anti-idiotypic A-Ab specific for the monoclonal anti-Tg A-Ab (3B8G9) paratope which binds to Tg determinant inducing EAT.

Induction of autoimmunity with dendritic cells: studies on thyroiditis in mice

The initiation and maintenance of thyroid autoimmunity by professional antigen-presenting cells were assessed by observing thyroiditis and induction of IgG antibodies to thyroglobulin (Tg). Dendritic cells (DC) were purified from spleens of CBA mice and T cells removed with anti-Thy 1 and complement. Some DC were pulsed with 25-500 micrograms/ml of mouse Tg in vitro and normal syngeneic mice received injections of 10(5) cells intravenously. In untreated animals only 1 thyroid out of 40 showed a lymphocyte infiltrate and antibody to Tg was rarely seen. In animals receiving normal DC without Tg, lymphocyte infiltration was seen 2-6 weeks later in 5 out of 33 thyroids and some animals produced low levels of antibody to thyroglobulin (8 of 33 animals). DC pulsed with 500 micrograms Tg/ml in vitro caused thyroid infiltration in 6 out of 15 animals but did not increase the incidence of anti-Tg antibodies. Lower doses had no effect. When 10(5) DC were given from animals with experimental allergic thyroiditis (EAT, induced with Tg in complete Freund's adjuvant, CFA) more than half of the recipient animals showed thyroiditis (8 out of 15) and autoantibody production (12 of 15 animals). DC may therefore play a role in the initiation and maintenance of autoimmunity by providing a stimulus for antigen-specific T cells.

Sequential analysis of experimental autoimmune thyroiditis induced by neonatal thymectomy in the Buffalo strain rat

We have studied the evolution of thyroiditis induced by neonatal thymectomy in Buffalo strain rats, with particular emphasis on the thyroid lymphocytic infiltrate. The earliest change was increased endothelial Ia expression, and infiltration of the thyroid at 5 weeks by ED1- and ED2-positive macrophages and B and T cells. The T cells comprised equal numbers of Ox 8 (T cytotoxic/suppressor)- and W3/25 (T helper)-positive cells. Ia-positive thyroid follicular cells were seen only in the presence of a T-cell infiltrate. Thyroglobulin antibody levels, thyroid weight, thyroid follicular cell Ia expression, and lymphocytic infiltration of the thyroid were maximal between Weeks 12 and 24, and impairment of macrophage function by injection of silica at this time produced amelioration of disease. The thyroid weight returned to control levels by Week 34 and Ia expression by thyroid cells disappeared. Circulating Ox 8-positive T cells were reduced between Weeks 12 and 24 and by Week 34 had returned to control levels. Our results indicate that the mononuclear infiltrate precedes thyroid follicular cell Ia expression and macrophages play an important role in perpetuating thyroiditis. Recovery from disease is accompanied by a return to normal in circulating suppressor/cytotoxic T cells.