Sensitization of T lymphocytes to thyroglobulin and thyroperoxidase in autoimmune thyroid diseases

Reduction in experimental autoimmune thyroiditis by IgG Fc fragments bearing regRF epitopes

Previously, we identified a new immunoregulatory factor, the production of which provides rats with resistance to certain experimental autoimmune diseases. It has been named regulatory rheumatoid factor (regRF). RegRF inhibits the expansion of CD4 T lymphocytes by killing activated cells. CD4 T cells are essential for antibody production against a majority of antigens and for the generation of cytotoxic T cells; therefore, regRF is an attractive therapeutic biotarget for T-cell and antibody-mediated autoimmune diseases. RegRF is anti-idiotypic antibodies that have a shared paratope in addition to an individual paratope. Epitopes specific to the shared regRF paratope (regRF epitopes) can be obtained on conformers of IgG Fc fragments. Immunization with Fc fragments carrying regRF epitopes reduces rat collagen-induced arthritis and diminishes experimental autoimmune encephalomyelitis. The aim of this study was to determine whether IgG Fc fragments bearing regRF epitopes suppress experimental autoimmune thyroiditis (EAT). Four weeks after EAT induction, rats were immunized with IgG Fc fragments exhibiting regRF epitopes. Histology studies of the thyroid were performed 4 weeks later. Thyroid function and other parameters were also evaluated. Treatment of rats with Fc fragments bearing regRF epitopes decreased the number of rats affected by EAT, significantly decreased the extent of thyroid damage, prevented thyroid metaplasia, and restored normal thyroid hormone production. Therefore, RegRF is a promising biotarget in autoimmune thyroiditis, and Fc fragments bearing regRF epitopes are a potential therapeutic agent for that condition.

Proliferative Responses to Canine Thyroglobulin of Peripheral Blood Mononuclear Cells from Hypothyroid Dogs

The immune responses of hypothyroid dogs to canine thyroglobulin (cTg) were evaluated for the proliferative ability of peripheral blood mononuclear cells (PBMC). PBMC from three hypothyroid dogs with high titers of thyroglobulin autoantibody (TgAA) and 3 clinically normal dogs were cultured with 5, 10, or 20 microg/ml of cTg for 72 hr. The proliferative responses of the cells were determined by the level of incorporated BrdU. The numbers of cells expressing Thy-1, CD4, CD8 and IgG in the PBMC were counted by the immunofluorescence method. Proliferative responses to cTg were observed in the cells from hypothyroid dogs. The number of cells expressing IgG and CD8 in the hypothyroid dogs tended to be high compared with the clinically normal dogs. The CD4+ cells in cultures from hypothyroid dogs increased depending upon the amount of cTg. There was a significant (P<0.05) positive correlation between the number of CD4+ cells and the concentration of cTg in the cultures from hypothyroid dogs. These findings suggest a possible relationship between canine hypothyroidism and cellular immunity. Loss of self tolerance to thyroid antigens in CD4+ T cells may play an important role in the development of canine hypothyroidism.

Whole-blood proliferation assay for autoimmune thyroid disease: comparison to density-gradient separated-peripheral blood lymphocytes

Autoimmune thyroid diseases feature prominent cellular infiltration of the thyroid gland as well as autoantibody production to thyroid antigens. The most common assay to evaluate cell-mediated immunity is based on incorporation of tritiated thymidine into proliferating T cells after stimulation by the test antigens. In the past, cell proliferation assays of thyroglobulin (Tg) using peripheral blood mononuclear cells (PBMC) of individuals with autoimmune thyroid diseases required large quantities of blood and specialized separation techniques, and have not yielded high counts or high stimulation indices. We therefore developed a proliferation assay using less than 5 mL of whole blood and compared proliferation of cells in whole blood to that using PBMCs separated by density gradient centrifugation. We also determined if responses could be enhanced by addition of interleukin-2 (IL-2) to the cultures. We found that an IL-2-stimulated proliferation assay to Tg using diluted whole blood is superior to the separated cell assay in detecting Tg-specific T-cell proliferation in autoimmune thyroid disease patients. Further refinement of this technique and larger trials may confirm its value for clinical investigation and special diagnostic applications.

Iodine is essential for human T cell recognition of human thyroglobulin

Here we describe for the first time that recognition by human T cells of human thyroglobulin depends upon its iodine content. We have examined the proliferation of lymphocytes from blood of autoimmune thyroiditis patients and normal individuals to thyroglobulin preparations containing different amounts of iodine. A minimal degree of iodination was required to elicit the proliferative response of both patients and normal individuals since thyroglobulin preparations containing no detectable iodine did not induce proliferation. A non-iodinated thyroglobulin preparation that was iodinated in vitro produced significant proliferation of both patient and normal lymphocytes. Addition of IL-2 to the culture medium enhanced proliferation but did not change the pattern of response.

The effect of adding a surfeit of autologous CD8+ T cells to SCID mice after secondary rexenografts of Graves' thyroid tissue

To investigate the effect of adding a surfeit of CD8+ T cells as a potential immunoregulator in Graves' disease (GD), thyroid tissues from 4 patients with GD and 2 normal subjects (N) were initially xenografted into nude mice. Eight weeks after xenografting, the thyroid tissues, which were then devoid of lymphocytes and appeared normal, were retrieved from the nude mouse, and rexenografted (rexenografts) into severe combined immuno-deficient (SCID) mice; 20 x 10(6) of autologous peripheral blood mononuclear cells (PMBC) or 20 x 10(6) of CD8(+)-depleted PBMC ("non-CD8 cells," i.e., CD4-enriched PBMC) were simultaneously engrafted into SCID mice with thyroid rexenografts. In addition, 20 x 10(6) of CD8(+)-enriched PBMC ("CD8-doubled" cells, which were prepared to double the percentage of CD8+ T cells compared to that of PBMC) were engrafted into SCID mice with rexenografts from 2 GD and 2 N; finally, 20 x 10(6) of PBMC plus an extra 10 x 10(6) of CD8+ T cells ("extra-CD8 added" cells, total 30 x 10(6) of CD8-enriched cells) were engrafted into separate SCID mice with rexenografts from 2 GD. The reengraftment of GD rexenografts or N rexenografts alone did not result in the detection of thyroperoxidase (TPO)-antibodies (Abs), thyroglobulin (Tg)-Abs, thyroid-stimulating Ab (TSAb) production, human IgG, or lymphocytic infiltration in the xenografts. However, the engraftment of either autologous PBMC or non-CD8 cells from patients with GD and N into SCID mice with rexenografts caused human IgG to become detectable and then rise further in 10 of 17 SCID mice; when human IgG, TPO-Ab, Tg-Ab, and TSAb were quantitated, GD rexenografts plus non-CD8 cells engrafted into SCID mice showed a higher production of each antibody and human IgG than in GD rexenografts plus PBMC, or GD rexenografts plus CD8-doubled cells, or GD rexenografts plus extra "CD8-added" cells. Moreover, when CD8-doubled cells or extra CD8-added cells with rexenografts were engrafted to SCID mice with rexenografts, they showed generally lower production of human IgG and thyroid antibodies compared to SCID mice into which PBMC were engrafted with rexenografts, despite the fact that 50% more cells (30 x 10(6)) were engrafted in the preparations of extra CD8-added cells. In conclusion, CD8+ T cells from patients with GD appeared to suppress the induction of thyroid antibodies, TSAb, and human IgG. The CD8+ cells thus are acting as suppressor or regulatory T cells. Such cells might be important in the pathogenesis of autoimmune thyroid disease.

T-cell responses to the components of pyruvate dehydrogenase complex in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune condition that results in destruction of the intrahepatic biliary epithelial cells and is characterized by autoantibodies to pyruvate dehydrogenase complex (PDC). The portal tract T-cell infiltrate and up-regulation of HLA class I, HLA class II, and cell adhesion molecules such as intercellular adhesion molecule-1 on the biliary epithelial cells suggest that T cells play a significant role in mediating this damage. The authors have characterized the peripheral blood T-cell proliferative responses of 24 PBC patients and 48 controls (20 normal, 28 non-PBC chronic liver disease) to the dominant autoantigen PDC, and its constituent components E1, E2 and protein X (which co-purify), and E3. A significant proportion of both PBC patients and controls showed T-cell responses to whole PDC (12 of 24 vs. 24 of 48 SI > 2.5 P = NS) and E1 (15 of 24 vs. 25 of 48 P = NS). Responses to PDC and E1 are thus seen in normal individuals and are not limited to PBC patients. T-cell responses to E2/X were seen in most PBC patients (14 of 24), but in only a small number of controls (6 of 48, P < .0001), responses to E2/X being significantly more frequent in pre-cirrhotic PBC patients (stages I to III, 12 of 15) than cirrhotic (stage IV, 2 of 9 P < .05). Peripheral blood T-cell responses to E2/X are thus strongly associated with early PBC. Responses to E3 were low in both PBC patients and controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies of human thyroid xenografts from Hashimoto's thyroiditis in severe combined immunodeficient (SCID) mice: detection of thyroid stimulation-blocking antibody

Human thyroid xenografts from 7 patients with Hashimoto's thyroiditis (HT) and 3 normal persons (N) were xenografted into severe combined immunodeficient (SCID) mice to study the intrathyroidal lymphocytes that were expected to survive in these animals. Human IgG was detected in all mice engrafted with HT thyroid tissue peaking at 6-10 weeks after xenografting. Thyroperoxidase-antibody (TPO-Ab) was also detected in all mice with HT thyroid grafts peaking at 4-6 weeks after xenografting, reaching up to 44% of donors' original concentrations. In contrast, maximal thyroglobulin (Tg)-Ab production in some SCID mice with HT thyroid grafts was higher than the donors' original level, and was detectable in mice with thyroid grafts from Tg-Ab-negative HT donors. Thyroid stimulation-blocking antibody (TSBAb) was found in 2 mice with thyroid xenografts from 1 HT patient whose original serum TSBAb and thyrotropin-binding inhibitor immunoglobulin (TBII) had been positive; the maximal TSBAb level in SCID mice exceeded the donor's original level. TSBAb production in SCID mice reached its peak at 10 weeks after xenografting, i.e., later than that of thyroid-stimulating antibody (TSAb) observed in our recent report, suggesting the existence of distinct intrathyroidal B cell autoreactive clones of different life span responsible for secreting TSAb or TSBAb. When autologous peripheral blood mononuclear cells (PBMC) were engrafted alone (without thyroid tissue), TSBAb was undetectable.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced activation of suppressor T lymphocytes by specific antigens in autoimmune thyroid disease

In order to study the activation of suppressor T lymphocytes by thyroid-specific antigens in autoimmune thyroid disease (AITD), we have investigated the effects of the organ-specific antigens, thyroperoxidase (TPO), thyroglobulin (Tg), and thyroid microsomal antigen (TMc), as well as renal microsomes (RMc) as a control antigen, on the activation of suppressor T lymphocytes; this was accomplished by measuring major histocompatibility complex class II (HLA-DR) expression on their surfaces by flow cytometric analysis. Peripheral blood mononuclear cells (PBMC), obtained from 33 patients with Graves' disease (GD), 26 with Hashimoto's thyroiditis (HT), 5 with nontoxic nodular goiter (NTG), and 30 normal persons (N), were cultured for 7 days in the presence or absence of TPO, Tg, or RMc at final concentration of 10, 100, and 1000 ng/ml. Cultured cells were stained with fluorescent-conjugated monoclonal antibodies (anti-CD8, anti-CD11b, and anti-HLA-DR), and the activation of CD8+ and CD8+CD11b+ (pure suppressor) T cells by the antigens was analyzed on a flow cytometer. In the absence of antigen, i.e., the autologous mixed lymphocyte reaction (AMLR), CD8+ and CD8+CD11b+ T lymphocytes from patients with GD and HT showed significantly lower activation as compared to N. We measured the Stimulation Index (Sl) of activated T lymphocytes to compare antigen-specific activation between CD8+ and CD8+CD11b+ cells from normal persons and patients. With stimulation of 100 and/or 1000 ng/mL of TPO or Tg, Sl of activated CD8+ cells was significantly (p < 0.05 to 0.01) lower in GD and HT as compared with N.(ABSTRACT TRUNCATED AT 250 WORDS)

Study of induction of activation of human peripheral blood mononuclear cells with a non-activating form of anti-CD3 MoAb in autoimmune thyroid disease (AITD)

Anti-CD3 (OKT3) MoAb is a mitogenic agent which activates lymphocytes. We have studied the effects of murine anti-human OKT3 MoAb (IgG1) alone or in combination with IL-2, human thyroglobulin (Tg) and thyroperoxidase (TPO) antigens on the proliferation of whole peripheral blood mononuclear cells (PBMC) (including monocytes) or subtypes (T, CD4+, CD8+, B) as measured by tritiated thymidine (3H-TdR) incorporation. B cell differentiation was studied by measuring numbers of IgG-secreting cells and specific anti-TPO/anti-Tg-secreting cells by SPOT ELISA. PBMC or lymphocyte subtypes, obtained from 45 patients with Hashimoto's thyroiditis (HT), 40 Graves' disease (GD) and 51 normal controls were cultured in 96 microtitre plates for 6 days in the presence of OKT3 MoAb at final concentrations 25-250 ng/ml, IL-2 15 U/ml, Tg and TPO (1 micrograms/ml). Then cultures were pulsed with 0.2 microCi 3H-TdR/well and incorporation was measured after 18 h. IgG and anti-TPO/Tg-secreting cells were detected at 7 days. Higher proliferative responses from whole PBMC preparations in response to any of the combinations including OKT3 MoAb were observed in the HT preparations, while the basal values were the lowest. IL-2 alone increased these responses markedly, but equally in all groups. IL-2 in combination with OKT3 had an additive effect on proliferation, with higher responses in HT. Tg and TPO antigens did not change these responses. Most HT preparations responded with their maximum proliferation to the lowest concentration of OKT3 MoAb (25 ng/ml), whereas in GD and control preparations of PBMC these responses were shifted to higher concentrations (250 ng/ml); even with those, proliferation was not so enhanced in controls when compared with HT and GD preparations. In contrast, the proliferative responses of T cells alone and subpopulations of CD8+ suppressor/cytotoxic cells were decreased in HT preparations compared with controls. Monocytes were necessary for proliferation. In the subpopulation of B cells (> 95% pure) and CD4+ helper/inducer cells, differences did not reach significance. In spite of the effect on proliferation, OKT3 MoAb only mildly but significantly increased the numbers of IgG-secreting cells in HT and GD preparations and did not stimulate synthesis of specific antibodies. Our data suggest that the increased proliferative responses of whole PBMC to OKT3 MoAb in HT preparations might be due to insufficient activation of T suppressor/cytotoxic cells.