6 autoimmunity Flashcards
What is autoimmunity?
Autoimmunity refers to immune responses mistakenly directed against the body’s own tissues.
What is an autoimmune disease?
Autoimmune diseases occur when autoimmunity leads to pathology despite normal immune regulatory mechanisms.
Are auto/self-reactive lymphocytes found in healthy individuals?
Yes, self-reactive T and B cells exist in people without autoimmune disease, but immune tolerance prevents them from causing pathology.
Why is autoimmune disease considered a hypersensitivity response?
Autoimmune diseases involve an excessive immune response against self-antigens, leading to tissue damage (similar to hypersensitivity reactions).
What are the two major classifications of autoimmune diseases?
Organ-specific autoimmune diseases (affecting one organ).
Systemic autoimmune diseases (affecting multiple organs).
Give an example of an organ-specific autoimmune disease and explain its mechanism.
Graves’ disease—autoantibodies against the TSH receptor lead to excessive thyroid hormone production.
Give an example of a systemic autoimmune disease and explain its mechanism.
Systemic Lupus Erythematosus (SLE)—autoantibodies to nuclear antigens form immune complexes, causing inflammation in skin, kidneys, and joints.
What causes Type 1 diabetes mellitus (T1D)?
CD8+ T cells destroy pancreatic β cells, leading to loss of insulin production.
What is Goodpasture’s syndrome?
Autoantibodies against type IV collagen in kidney and lung basement membranes lead to inflammation and damage.
How does Myasthenia Gravis impair muscle function?
Autoantibodies against acetylcholine receptors lead to their internalisation and degradation, preventing muscle contraction.
What happens in Hashimoto’s thyroiditis?
: Autoantibodies and T cells attack the thyroid, leading to hypothyroidism.
How does autoimmune pernicious anaemia develop?
Autoantibodies attack intrinsic factor, preventing vitamin B12 absorption and causing anaemia.
What is autoimmune Addison’s disease?
Autoantibodies destroy the adrenal cortex, leading to cortisol deficiency.
What causes vitiligo?
Autoimmune destruction of melanocytes leads to loss of skin pigmentation.
What is the main cause of rheumatoid arthritis (RA)?
Autoreactive CD4+ T cells activate macrophages and fibroblasts, producing inflammatory cytokines (e.g., TNF-α) that destroy joints.
How does scleroderma affect the body?
Autoimmune attack leads to excessive fibrosis and collagen deposition in skin and internal organs.
What autoantibodies are found in SLE?
Anti-nuclear antibodies (ANA), including those against DNA and histones, form immune complexes.
What is Sjögren’s syndrome?
Autoimmune attack on salivary and lacrimal glands, leading to dry eyes and dry mouth.
What is polymyositis?
T cell-mediated attack on muscle fibres, causing muscle weakness.
How do autoimmune diseases initiate?
Similar to normal immune responses—innate immune cells detect antigens, leading to T cell activation (often TH1 or TH17 responses).
What is the role of PAMPs in autoimmunity?
Some self-antigens may be presented in an inflammatory context (e.g., via TLRs) that mimics infection, leading to T cell activation.
How do autoantibodies cause disease?
Through molecular interference, cellular destruction, or immune complex formation.
What type of hypersensitivity reaction occurs in Graves’ disease?
Type II hypersensitivity—agonistic autoantibodies activate the TSH receptor, leading to hyperthyroidism.
What type of hypersensitivity occurs in autoimmune haemolytic anaemia?
Type II hypersensitivity—autoantibodies target red blood cells, leading to complement-mediated lysis.