Hypersensitivity III/IV Flashcards
What is Type III hypersensitivity?
Type III hypersensitivity is an immune complex disease, where antibodies and antigens form complexes that aren’t removed from circulation or are deposited in tissues. Cannot be regulated due to being excessively small/large size.
How are immune complexes typically removed (without hypersensitivity)?
Immune complexes are removed via the activation of the complement system, where C3b is deposited on the immune complex and binds to CR1 receptor which cause phagocytosis.
What is systemic IC disease?
IC disease is when the small complexes are deposited, increasing vascular permeability, neutrophil/monocyte recruitment and platelet activation leading to local ischemia.
If the complexes are placed in the blood vessels, what disease occurs?
Vasculitis
If the complexes are placed in the renal glomeruli, what disease occurs?
Glomerulonephritis
If the complexes are placed inbetween joints, what disease occurs?
Rheumatoid arthritis
What is arthus reaction?
Arthus reaction is a form of local type III hypersensitivity. Occurs as pre-existing antibodies diffuse across the vascular wall and induce inflammation. Can lead to edema, hemorrhage and ulceration.
What is acute post infection glomerulonephritis?
Post infection glomerulonephritis follows a strep infection or pharynx. Immune complexes form between strep antigens and antibodies, which go into the blood stream and deposit into glomeruli.
What is systemic lupus erythematosus?
SLE is an example of type III hypersensitivity, occurring from the failure to maintain self-tolerance. Too many antibodies are made, or they aren’t cleared.
Is unpredictable and can be relapsing. Immune complexes can occur in skin, kidney, joints, heart (for classification must have 4 or more symptoms)
What is Type IV hypersensitivity?
Type IV hypersensitivity is t-cell mediated hypersensitivities due to too many CD4 or CD8 t-cells, is triggered by an intracellular antigen.
What causes CD4 t-cell mediated hypersensitivity?
CD4t-cell hypersensitivity is caused by the secretion of cytokines, which results in the recruitment of macrophages causing t-cells to accumulate.
What’s an example of CD4 t-cell mediated Type IV hypersensitivity?
Tuberculin Reaction - t-cell mediated inflammatory response due to prior exposure.
Mtb granuloma formation - prolonged DTH reaction to a persistent microbe. Occurs in tuberculosis. CD4+ infiltrate and are replaced by macrophages, causing formation of giant cells.
What is an example of CD8 t-cell mediated type IV hypersensitivity?
Poison ivy, CD8+ cells respond to pentadecacatechol chemical present in poison ivy. The chemical is lipid soluable and modifies intracellular proteins - changing the peptides that MHC I present. So CD8+ directly kill these altered cells.
