Autoimmunity Flashcards
What prevents autoimmune diseases in healthy individuals?
Thymic deletion of self-reactive T cells peripheral anergy Tregs suppressing self-reactive T cells and negative selection of B and T cells
What is the role of the AIRE gene in autoimmunity prevention?
AIRE facilitates thymic expression of tissue-specific antigens for T cell negative selection
What factors influence the development of autoimmune diseases?
Genetics HLA alleles environmental triggers infection hormonal factors and defective tolerance mechanisms
What is the relationship between HLA and autoimmune diseases?
Most autoimmune diseases are strongly linked to Class II HLA alleles implicating CD4+ T cells in pathogenesis
What are examples of antibody-mediated autoimmune diseases?
Myasthenia gravis Graves’ disease systemic lupus erythematosus SLE
What are examples of cell-mediated autoimmune diseases?
Type 1 diabetes rheumatoid arthritis multiple sclerosis
What is the difference between tissue-specific and systemic autoimmune diseases?
Tissue-specific diseases target a single organ such as Type 1 diabetes while systemic diseases affect multiple systems such as SLE
What is molecular mimicry in autoimmunity?
Viral or bacterial antigens resemble self-antigens triggering cross-reactive immune responses
What are examples of localized antibody-mediated autoimmune diseases?
Myasthenia gravis acetylcholine receptor autoantibodies and Graves’ disease TSH receptor autoantibodies
What is the mechanism of Graves’ disease?
Autoantibodies against the TSH receptor act as agonists stimulating thyroid hormone production and causing hyperthyroidism
What is the mechanism of Hashimoto’s thyroiditis?
Autoantibodies against the TSH receptor act as antagonists inhibiting thyroid hormone production and causing hypothyroidism
What are examples of systemic antibody-mediated autoimmune diseases?
Haemolytic anemia RhD antigen Goodpasture’s syndrome type IV collagen and SLE nuclear antigens
What are the pathogenic mechanisms of autoantibodies?
Blocking or activating receptors complement-mediated lysis and immune complex formation causing inflammation
What is the role of Tregs in maintaining tolerance?
Tregs suppress self-reactive T cells and limit autoimmune responses by producing IL-10 and TGF-beta
What is the significance of HLA-B27 in ankylosing spondylitis?
HLA-B27 is strongly associated with ankylosing spondylitis implicating CD8+ T cells in disease development
What are the hormonal influences on autoimmunity?
Females are more susceptible to autoimmune diseases due to hormonal differences and stronger immune responses
What is the role of X-chromosome inactivation in autoimmunity?
Incomplete inactivation may lead to increased expression of proinflammatory genes contributing to autoimmunity in females
What is the role of environmental factors in autoimmunity?
Factors like infections diet pollution and smoking can trigger autoimmune diseases in genetically susceptible individuals
What is coeliac disease?
An autoimmune reaction to gluten associated with HLA-DQ2 and DQ8 causing damage to the gut epithelium
What is the hygiene hypothesis in autoimmunity?
Reduced exposure to infections in developed countries increases the risk of autoimmune diseases by limiting immune system development
What are common autoimmune diseases associated with HLA-DR alleles?
Rheumatoid arthritis DR4 multiple sclerosis DR2 SLE DR3 and Type 1 diabetes DR3 or DR4
What is the role of CD4+ T cells in autoimmune diseases?
CD4+ T cells mediate tissue damage through cytokines and help activate autoreactive B cells and CD8+ T cells
What are the mechanisms of cell-mediated autoimmune diseases?
CD4+ T cells release proinflammatory cytokines or attract macrophages and neutrophils and CD8+ T cells directly kill host cells
What is Type 1 diabetes and its link to HLA-DQ alleles?
Type 1 diabetes is strongly linked to HLA-DQ2 and DQ8 alleles which bind insulin and other peptides to activate autoreactive T cells
How do infections trigger autoimmunity?
Infections cause inflammation tissue damage and release of self-antigens which may activate autoreactive T or B cells
How does narcolepsy relate to autoimmunity?
Linked to HLA-DR2 and triggered by loss of hypocretin neurons due to CD8+ T cells targeting these neurons
How does haemolytic disease of the newborn involve autoimmunity?
Maternal anti-Rh antibodies cross the placenta and destroy fetal red blood cells if the fetus is Rh positive
What is the best treatment for coeliac disease?
Complete avoidance of gluten-containing foods
