Hypersensitivity & Autoimmunity Flashcards
What is an allergy?
A hypersensitive B lymphocyte reaction to usually harmless antigens. It is a multi-factorial function and B cells inappropriately produce IgE and Th cells are misdirected
What are the 4 mechanisms of hypersensitivity?
Type I, Type II, Type III and Type IV
What is Type I hypersensitivity?
It is an immediate mechanism, which is an allergy. The body recognises an environmental antigen as a pathogen and produces IgE which triggers a mast cell response.
What is the most common type of hypersensitivity?
Type I
What is IgE?
It is an antibody produced by humans that binds to eosinophils, basophils and mast cells. It has a specific structure of an extra peptide sequence
What is Type 2 hypersensitivity?
Antibodies bind to antigens on its own surface or fixed into tissues. Antibodies are produced and it is IgG and IgM mediated
What is the function of IgG and IgM?
They trigger the complement system which leads to cell lysis
What causes Type 2 hypersensitivity?
Miss-matched blood transfusions and rhesus antigens
What is Type 3 hypersensitivity?
The formation of complexes which are clumps of antibodies that have stuck together. This is a result of pathological conditions, which includes the problems with the antigens or host response
What are small complexes?
Low concentration of antibodies couples to high concentrations of antigens
What is Type 4 hypersensitivity?
It is a delayed mechanism that starts to produce cytokines as a result of CD4 Th1 cells recognising foreign antigens.
What does Type 4 hypersensitivity lead to?
The inflammatory response
What is involved in the early phase response of the Type 1 mechanism?
Mast cell mediators (histamine, heparin and chemotactic factors). It is a quick response, lasting only minutes
What is involved in the late phase response of the Type 1 mechanism?
Newly synthesised mediators, Th2 cytokines and eosinophil mediators. This response lasts for hours
In what type of mechanism is the the immune complex formed?
Type 3
What are the 2 types of immune complex formation?
Localised and Systematic
What does localised immune complex formation cause?
Localised inflammation that can be cleared away by macrophages
What does systematic immune complex formation cause?
Complexes that are deposited in tissues and organs e.g. skin, kidneys and BVs
What type of mechanism is autoimmune disease?
Type 3
What is autoimmune disease?
It is a large group of clinical disorders that are characterised by tissue or organ damage. It is mediated by incorrect immune mechanisms at self-antogens
What is failed as a result of autoimmune disease?
Tolerance
What causes autoimmune disease?
Genetic factors, Immune regulatory factors, Hormonal factors, Environmental factors and Other factors
What are immune regulatory factors?
Defects of peripheral or central tolerance
What are the 3 organ specific areas that are affected by autoimmune disease?
Thyroid, Stomach and Adrenal organs
What are the types of autoimmune disease that affects the thyroid?
Hashimoto’s thyroiditis, Primary myxoedema and Thyrotoxicosis
What are the types of autoimmune disease that affects the stomach?
Pernicious anaemia
What are the types of autoimmune disease that affects the adrenal organs?
Addison’s disease
What are the 4 non-organ specific areas affected by autoimmune disease?
Muscles, Skin, Kidneys and Joints
What are the types of autoimmune disease that affects the muscles?
Dermatomyositis
What are the types of autoimmune disease that affects the skin?
Scleroderma
What are the types of autoimmune disease that affects the kidneys?
SLE
What are the types of autoimmune disease that affects the joints?
Rheumatoid arthritis
What is a hapten?
Lower molecular weight agent where the immune reposes is targeted
