Studies on experimental thyroiditis

T cells, α-synuclein and Parkinson disease

The notion that autoimmune responses to α-synuclein may be involved in the pathogenesis of this disorder stems from reports that mutations in α-synuclein or certain alleles of the major histocompatibility complex (MHC) are associated with the disease and that dopaminergic and norepinephrinergic neurons in the midbrain can present antigenic epitopes. Here, we discuss recent evidence that a defined set of peptides derived from α-synuclein act as antigenic epitopes displayed by specific MHC alleles and drive helper and cytotoxic T cell responses in patients with PD. Moreover, phosphorylated α-synuclein may activate T cell responses in a less restricted manner in PD. While the roles for the acquired immune system in disease pathogenesis remain unknown, preclinical animal models and in vitro studies indicate that T cells may interact with neurons and exert effects related to neuronal death and neuroprotection. These findings suggest that therapeutics that target T cells and ameliorate the incidence or disease severity of inflammatory bowel disorders or CNS autoimmune diseases such as multiple sclerosis may be useful in PD.

Spontaneous (Hashimoto-like) chronic lymphocytic thyroiditis in a rhesus macaque (Macaca mulatta)

A case of a female, 10-year-old rhesus macaque (Macaca mulatta) with spontaneous chronic lymphocytic thyroiditis is presented. At necropsy, the thyroid gland was slightly enlarged, with up to 2 mm large, round, confluent, beige foci on the surface of both lobes. Histopathologic features resembled human Hashimoto's thyroiditis: multifocally, the interstitium was infiltrated by lymphocytes and variably sized lymphoid follicles. In the pituitary gland, there were increased numbers of large, basophilic cells throughout the adenohypophysis. Using a human electrochemiluminescence immunoassay (ECLIA), no autoantibodies against thyroglobulin, thyroid peroxidase, or thyroid-stimulating hormone receptor were detected.

Cardiac antibody production to self-antigens in children and adolescents during and following the correction of severe diabetic ketoacidosis

Diabetic cardiomyopathy (DC) is an independent phenotype of diabetic cardiovascular disease. The understanding of the pathogenesis of DC in young patients with type 1 diabetes (T1D) is limited. The cardiac insults of diabetic ketoacidosis (DKA) and progression of DC could include development of antibodies (Abs) to cardiac self-antigens (SAgs) such as: myosin (M), vimentin (V) and k-alpha 1 tubulin (Kα1T). The goal of this study is to determine if the insults of severe DKA and its inflammatory cascade are associated with immune responses to SAgs. Development of Abs to the SAgs were determined by an ELISA using sera collected at three time points in relation to severe DKA (pH < 7.2). Results demonstrate significant differences between the development of Abs to VIM and a previously reported diastolic abnormality (DA) during DKA and its treatment and a NDA group at 2-3 months post DKA (p = 0.0452). A significant association is present between T1D duration (<3 years) and Abs to Kα1T (p = 0.0134). Further, Abs to MYO and VIM are associated with inflammatory cytokines. We propose that severe DKA initiates the synthesis of Abs to cardiac SAgs that are involved in the early immunopathogenesis of DC in young patients with T1D.

Breaking tolerance to thyroid antigens: changing concepts in thyroid autoimmunity

Thyroid autoimmunity involves loss of tolerance to thyroid proteins in genetically susceptible individuals in association with environmental factors. In central tolerance, intrathymic autoantigen presentation deletes immature T cells with high affinity for autoantigen-derived peptides. Regulatory T cells provide an alternative mechanism to silence autoimmune T cells in the periphery. The TSH receptor (TSHR), thyroid peroxidase (TPO), and thyroglobulin (Tg) have unusual properties ("immunogenicity") that contribute to breaking tolerance, including size, abundance, membrane association, glycosylation, and polymorphisms. Insight into loss of tolerance to thyroid proteins comes from spontaneous and induced animal models: 1) intrathymic expression controls self-tolerance to the TSHR, not TPO or Tg; 2) regulatory T cells are not involved in TSHR self-tolerance and instead control the balance between Graves' disease and thyroiditis; 3) breaking TSHR tolerance involves contributions from major histocompatibility complex molecules (humans and induced mouse models), TSHR polymorphism(s) (humans), and alternative splicing (mice); 4) loss of tolerance to Tg before TPO indicates that greater Tg immunogenicity vs TPO dominates central tolerance expectations; 5) tolerance is induced by thyroid autoantigen administration before autoimmunity is established; 6) interferon-α therapy for hepatitis C infection enhances thyroid autoimmunity in patients with intact immunity; Graves' disease developing after T-cell depletion reflects reconstitution autoimmunity; and 7) most environmental factors (including excess iodine) "reveal," but do not induce, thyroid autoimmunity. Micro-organisms likely exert their effects via bystander stimulation. Finally, no single mechanism explains the loss of tolerance to thyroid proteins. The goal of inducing self-tolerance to prevent autoimmune thyroid disease will require accurate prediction of at-risk individuals together with an antigen-specific, not blanket, therapeutic approach.

Adjuvant immunization induces high levels of pathogenic antiphospholipid antibodies in genetically prone mice: another facet of the ASIA syndrome

Adjuvants may induce autoimmune diseases in susceptible individuals, a phenomenon recently defined as autoimmune/inflammatory syndrome induced by adjuvants (ASIA). Patients with both antiphospholipid antibodies (aPL) and the genetic coagulopathy factor V Leiden (FVL) are frequently found. We therefore evaluated whether adjuvant can induce aPL in heterozygous FVL mice. aPL were measured in naïve mice and at 1 and 5 months after immunization with either complete or incomplete Freund's adjuvant (CFA, IFA) in FVL and control C57/B6 background mice. We defined antibody levels 3 SD above the mean of C57/B6 mice immunized with adjuvant as positive (specificity of 99%). For β(2)GPI-dependent aPL, 28.6% (6/21) of FVL mice 5 months after immunization with adjuvant (both IFA and CFA) were positive compared with 4.8% (1/22) of FVL mice 1 month after adjuvant and 0% of naïve FVL and C57/B6 mice (0/16, p < 0.001). aPL levels correlated with behavioral hyperactivity in the staircase test. FVL mice immunized with adjuvant did not develop β(2)GPI-independent aPL. We hypothesize that the FVL aPL association is not a coincidence, but that chronic coagulation defects combined with external inflammatory stimuli analogous to adjuvant may induce aPL and also antiphospholipid syndrome, thus supporting the notion of ASIA.

Response to experimental infection with mumps virus in rhesus monkeys

Experiments were conducted in which rhesus monkeys were infected with mumps virus by inoculation into the parotid gland. Virus was isolated from buccal swab specimens from animals up to 6 days after inoculation. Immunofluorescence staining for mumps antigen was positive, and infectious virus was recovered from tissue biopsies of inoculated glands. Histological examination of biopsied glands revealed lymphocytic infiltration of the tissue. Virus was not isolated from urine, buffy coat, or biopsies of thyroid and spleen. In other experiments, animals were infected by inoculation into the thyroid gland. Virus was not isolated from buccal swabs, urine specimens, or thyroid tissues from these monkeys. All inoculated animals responded immunologically to mumps virus regardless of route of infection. Previously infected animals did not shed virus when challenged with mumps virus. A histological response to challenge in glandular tissue was observed which suggested a hypersensitivity to mumps antigen. The response was qualitatively identical to that in acutely infected tissue but more intense. None of the animals infected developed antibodies to thyroid tissue regardless of route of injection of virus or site of challenge of immune monkeys.

Sjogrens syndrome as failed local immunohomeostasis: prospects for cell-based therapy

Sjogrens syndrome has been estimated to affect between 0.2% and 2% or more of the population. It is an autoimmune disease with the hallmark histopathology of focal, periductal, and perivascular CD4(+) cell infiltration of the lacrimal and salivary glands. The immunohistopathology is typically associated with severe lacrimal and salivary dysfunctions, which contribute to debilitating ocular surface and oral symptoms. The quality of life of patients with Sjogrens syndrome often is degraded further by serious, multisystemic manifestations, and they are subject to a forty-fold increased risk of developing B cell lymphomas. In normal lacrimal glands, secretory epithelial cells, autoimmune effector lymphocytes, and regulatory lymphocytes can be seen as collaborating to maintain a local immunohomeostasis. The epithelium contributes by secreting immunomodulatory paracrine factors and also by continuously exposing autoantigens, which thereby become available for uptake by professional antigen presenting cells (APCs). Local or systemic perturbations may initiate autoimmune pathophysiology by impairing the replacement of normally-turning-over regulatory cells, by altering epithelial production of immunomodulatory paracrine factors, by inducing intact epithelial cells to begin secreting previously cryptic epitopes (epitopes that previously were not available to bind to major histocompatibility complex (MHC) molecules and so could not be recognized by T cell antigen receptors), and by inducing epithelial cells to begin expressing MHC Class II molecules and presenting formerly cryptic epitopes directly to CD4(+) cells. This process has been modeled ex vivo with mixed cell reactions comprised of isolated epithelial cells and autologous lymphocytes. This development has occurred as studies of anterior chamber-associated immune deviation (ACAID) and other immunoregulatory phenomena have elucidated the origins and functions of several different kinds of regulatory lymphocytes and shown that regulatory lymphocytes can be generated ex vivo. It now is possible to envision strategies for exploiting each possible mode of epithelial autoantigen exposure to produce therapeutic regulatory cells that might be capable of re-establishing normal immunohomeostasis. Consideration of the hypothetical therapies identifies a number of basic questions that warrant investigation.

The basis of autoimmunity: an overview

Autoimmune diseases represent a failure of control in the immune system. In recent years, our understanding of the mechanisms of action of both the innate and the specific immune responses has increased greatly. In particular, we now know much more about the nature of antigens recognized by lymphocytes, as well as how diversity of antigen receptors is generated, antigens and antigen receptors interact, and the cells of the immune system communicate. It is apparent that an inevitable consequence of the diversity of the potential response to antigen is self-reactivity. However, the relative infrequency with which pathological self-reactivity occurs implies the existence of effective control of immune responses. The conditions under which immune responses can be activated, and the factors which regulate their progression, have been subjected to detailed scrutiny. Several of the mechanisms involved in the removal or inactivation of self-reactive lymphocytes, the process of self-tolerance, are now understood. What is less clear are the conditions under which, and the mechanisms by which, this self-tolerance can break down, giving rise to autoimmunity. Several classes of explanation have been put forward to explain this failure of self-tolerance. Although they are of great theoretical interest, proof of their involvement in the pathogenesis of the major autoimmune diseases is largely lacking. A further expansion of our understanding of the mechanisms by which self-tolerance is normally maintained is still needed, in order to comprehend the pathways of breakdown of this tolerance in autoimmunity. Only then will sites and mechanisms for effective therapeutic intervention be identified.

Immunologic studies of male infertility

Infertile men with azo- or oligospermia of unknown cause were investigated for evidence of testicular autoimmunity. Testicular germinal cell antibodies were found in 14% of the patients, compared with 5% of normal men, and 21% had spermatozoal antibodies, compared with 5% of the normal subjects. One-third had positive macrophage inhibitory factor tests, compared with 5% of normal subjects. However, of autoantibodies against thyroid, stomach, and nuclear material, only the prevalence of thyroid cytoplasmic antibodies was significantly greater than in normal subjects; serum IgG, IgM, and IgA levels were normal in all cases tested. Furthermore, there was no excess of lymphoid tissue on biopsy and no evidence of antibody deposition in the testicular tissue. The evidence for autoimmunity is less impressive than that for leprous orchitis, which has been proposed as a model for testicular organ-specific autoimmunity. Nevertheless, it is possible that certain germinal cell or spermatozoal antibodies may be directed against factors necessary for orderly spermatogenesis. If so, they may play a role in some cases of maturation arrest and shedding defects.

Insoluble particulate antigen(s) in cell-mediated immunity of autoimmune thyroid disease

Cell-mediated immunity (CMI) in patients with Grave's disease, chronic thyroiditis, and primary hypothyroidism was observed by assay of lymphocyte-mediated cytotoxicity (LMC) and leukocyte migration inhibition (LMC). Lymphocyte responsivity to phytohemagglutinin (PHA) is normal in these disease. In the LMC assay, lymphocytes of patients in each category responded to the antigens of thyroid homogenates, but not purified human thyroglobulin. Cytotoxicity is least in Graves disease and most obvious in primary hypothyroidism. In the LMI assay, patients lymphocytes responded to thyroid microsomal--mitochondrial antigens, but not to thyroid cell sap. Lymphocytes of Graves disease patients also responded to liver microsomal mitochondrial antigens. The particulate antigens lost activity when solubilized by ultrasonication or KCL extraction. There is no correlation between the PHA responsivity of lymphocytes and thyroid function, or between CMI and serum antithyroid antibodies or thyroid size. Treated and untreated patients had similar evidence of CMI. These data indicate that function of thymus-derived lymphocyte in vitro is not disturbed in autommune thyroid disease and that CMI against thyroid antigens can be demonstrated by assay of LMC and LMI. Insoluble particulate antigens appear more important than soluble antigens in CMI. LMC, resumably induced by soluble cytotoxic factor, "lymphotoxin," may play an important role in the progress of the autoimmune thyroid disease to hypothyroidism.

Autoimmune murine thyroiditis relation to histocompatibility (H-2) type

Immunization of 33 inbred strains of mice with thyroid extract emulsified in complete Freund's adjuvant showed differences in both thyroid autoantibody response and autoimmune thyroid damage, related to the histocompatibility (H-2) type of the strain. Congenic mice of the same H-2 type exhibited the same pattern of antibody response and thyroiditis, regardless of the strain's genetic background, thus showing a close relation between histocompatibility determinants and autoimmunity.

The role of mycobacteria and the effect of proteolytic degradation of thyroglobulin on the production of autoimmune thyroiditis

Data are presented which suggest that the initial event involved in experimental autoimmune thyroiditis following injection of rabbits with homologous thyroglobulin in complete Freund's adjuvant is alteration of the thyroglobulin. Alteration of the thyroglobulin does not occur during incorporation into the adjuvant or in vitro storage in the adjuvant, and the mycobacteria in the adjuvant have no direct effect on the thyroglobulin. Most likely, the alteration results from an increase in hydrogen ion concentration within cells or local areas in the granuloma and the subsequent action of proteolytic enzymes. These conditions are probably established in the granuloma as the result of neutrophilic response to the mycobacteria in the adjuvant. Rabbits injected with aqueous preparations of homologous thyroglobulin partially degraded in vitro with pepsin at acid pH produced antibody to native thyroglobulin and developed thyroiditis. Most of these rabbits responded to a subsequent injection of native thyroglobulin given 1 month later.