Ko Flashcards
What is hypersensitivity?
Hypersensitivity refers to undesirable reactions produced by the normal immune system, representing a heightened state of immune responsiveness to a harmless antigen. These exaggerated responses can lead to tissue injury, disease, or even death.
How are hypersensitivity reactions classified?
Hypersensitivity reactions are categorized into four types based on their underlying mechanisms and reaction time.
What is Type I hypersensitivity?
Type I hypersensitivity, also known as immediate hypersensitivity, involves IgE antibodies binding to mast cells and basophils. Upon re-exposure to the allergen, cross-linking of IgE Fc-receptors triggers the release of mediators like histamine and leukotrienes.
What are examples of Type I hypersensitivity?
Examples include anaphylaxis and hay fever.
What is the mechanism of Type I hypersensitivity?
IgE has very high affinity for its receptor on mast cells or basophils. A subsequent exposure to the same allergen cross-links the cell-bound IgE and triggers the release of various pharmacologically active substances.
How is Type I hypersensitivity diagnosed?
Diagnosis includes skin tests and measurement of total and allergen-specific IgE.
What is the treatment for Type I hypersensitivity?
Treatment includes antihistamines, leukotriene receptor blockers, and mast cell stabilizers like cromolyn sodium.
What is Type II hypersensitivity?
Type II hypersensitivity, also known as cytotoxic hypersensitivity, involves free antibodies (IgG or IgM) reacting with antigens on cell surfaces, leading to cell lysis via complement activation or antibody-dependent cell-mediated cytotoxicity (ADCC).
What are examples of Type II hypersensitivity?
Examples include transfusion reactions and autoimmune hemolytic anemia.
How is Type II hypersensitivity diagnosed?
Diagnosis includes detection of circulating antibodies against target tissues and immunofluorescence of biopsy samples.
What is the treatment for Type II hypersensitivity?
Treatment includes immunosuppressive agents and plasmapheresis.
What is Type III hypersensitivity?
Type III hypersensitivity, also known as immune complex hypersensitivity, occurs when soluble antigen-antibody complexes deposit in tissues, activating complement and attracting neutrophils, leading to inflammation and tissue damage.
What are examples of Type III hypersensitivity?
Examples include serum sickness, systemic lupus erythematosus (SLE), and rheumatoid arthritis.
How is Type III hypersensitivity diagnosed?
Diagnosis includes immunofluorescence of biopsies to detect immune complex deposits and serum complement levels.
What is the treatment for Type III hypersensitivity?
Treatment includes anti-inflammatory agents and corticosteroids.
