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Most autoimmune diseases are caused by a
Identifying an autoimmune disease in humans is often accomplished by
The following is/are possible mechanism(s) for the recognition of self-components
by the immune system in autoimmune diseases:
Rheumatoid factor, found in synovial fluid of patients with rheumatoid arthritis, is
most frequently found to be
The pathology in autoimmune diseases due to antibody may be a result of
Autoimmune hemolytic anemia:
Systemic lupus erythematosus
Diseases in which TH cells and cytotoxic CD8+ T cells probably play major roles in their pathology include all of the following except
A patient is found to have a form of diabetes in which his immune system is destroying his pancreatic islet cells. Which is the most likely explanation for this disease state?
Hashimoto's thyroiditis
Case Study A 17-year-old boy suffered an injury to his left eye when, during a car crash, a sharp sliver of glass penetrated his eye, damaging his lens and uveal tract. The glass was removed and the injury repaired with complete recovery. However, 3 weeks later he noticed some redness in the left eye and photophobia, followed by pain and severe visual impairment. The left eye was removed, and histologic examination showed an extensively infiltrated uveal tract with abundant lymphocytes and mononuclear cells. Two weeks later the other eye began to show the same symptoms. What is going on, and what could be done?Answers To Review Questions 1. C The etiologies of most autoimmune diseases appear to be multifactorial and require a combination of genetic and environmental events to manifest themselves. 2. D For most human autoimmune disease circumstantial evidence is used. Merely finding an antibody to self-components does not imply that there is a disease condition. T cells or antibodies are the cause of tissue damage in many diseases, such as infectious disease, and does not necessarily mean that the disease is an autoimmune one. Passive transfer of T cells is difficult in humans and in most autoimmune diseases, no definitive agent or agents have been identified. The best answer is D. 3. E Self-reactive T and B cells may be activated by any of the mechanisms listed. 4. B Rheumatoid factor is generally an IgM antibody that reacts with Fc determinants on the H chain. 5. E All are possible causes of antibody-induced autoimmune disease. 6. B Warm agglutinins belong to the IgG class; cytotoxic T cells are not known to cause autoimmune hemolytic anemia; complement is a frequent participant in lysis or opsonization; the Coombs test is frequently positive for either IgG, IgM or C3 in patients with autoimmune hemolytic anemia. 7. C Systemic lupus erythematosus affects skin, kidneys, heart, and joints. Symptoms are due to immune complexes that lodge in those areas and induce damage via activation of complement and infiltration of leukocytes. DNA may be involved as an antigen, but mutation plays no role, and the disease is initiated primarily by antibodies and is not considered a classic T-cell disease. 8. A Antibody has been implicated in myasthenia gravis both from experimental animal models and the fact that neonatal form can be transferred through the placenta from mother to baby. The other diseases listed are primarily cell mediated by effector T cells. 9. C One of the currently favored mechanisms for type 1 diabetes is an autoimmune response in which CD4+ TH cells specific for islet cells which have upregulated the expression of MHC class II molecules become activated and participate in the inflammatory reaction. Cytotoxic T cells and other immune cells cause the death of the b cells leading to insulin-dependent diabetes. 10. B. Hashimoto's thyroiditis is thought to be a T-cell-mediated disease, some features of which can be found in an experimental model by immunization of animals with thyroglobulin in adjuvant. Answer to Case Study The most likely diagnosis is of a rare case of sympathetic ophthalmia, an autoimmune disease in which trauma to uveal, retinal, and lens tissues releases antigens that induce T-cell-mediated responses. Once generated, these T cells attack the damaged eye and induce a granulomatous uveitis. They also have the potential for attacking the healthy eye, producing the same damaging effects. The diagnosis could be confirmed by the appearance of positive delayed-type reactions following skin testing with an extract of bovine uveal tissue, which cross-reacts immunologically with human uveal tissue. A safe procedure would be to look for an in vitro proliferative response of the patient's peripheral blood lymphocytes when exposed to the same antigen. Immunosuppressive therapy with topical or systemic corticosteroids is useful in mild cases. Removing the damaged eye is the only way to prevent the onset of the autoimmune reaction. In these cases, clinicians must weigh the chances of maintaining useful vision in the injured eye against the risk of an autoimmune reaction with possible loss of both eyes.
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