Hypersensitivity Reactions Flashcards
What occurs in individuals who have been previously exposed to an antigen?
Hypersensitivity reactions
What characterizes the immediate reaction in Type I hypersensitivity?
Vasodilation, congestion, and edema
What mediates Type I hypersensitivity reactions?
IgE antibodies that bind to allergens and activate mast cells
What symptoms are associated with systemic anaphylaxis?
Vascular shock, widespread edema, difficulty breathing
What characterizes Type II hypersensitivity?
Antibodies directed towards antigens on the surface of cells or in the extracellular matrix
Which receptor is involved in Graves disease, a Type II hypersensitivity reaction?
Thyroid-stimulating hormone receptor
What occurs in Type III hypersensitivity?
Deposition of immune complexes in tissues, leading to conditions like vasculitis and glomerulonephritis
What cells mediate delayed-type hypersensitivity (Type IV)?
CD4+ T cells
What is a common example of a delayed-type hypersensitivity reaction?
The tuberculin reaction
What occurs in Type IV hypersensitivity in response to persistent antigens like tuberculosis bacilli?
Granuloma formation
What characterizes the late-phase reaction in Type I hypersensitivity?
Infiltration of eosinophils, neutrophils, and T cells
What genetic predisposition is associated with localized immediate hypersensitivity reactions to allergens?
Atopy
What is a mechanism in Type II hypersensitivity that leads to cell destruction?
Opsonization and phagocytosis
What disease exemplifies Type II hypersensitivity causing cellular dysfunction?
Myasthenia gravis
What are examples of Type III hypersensitivity diseases?
Systemic lupus erythematosus and poststreptococcal glomerulonephritis
What immune system activation triggers acute inflammatory reactions in immune complex-mediated hypersensitivity?
Complement system activation
What is the localized tissue necrosis caused by acute immune complex vasculitis called?
Arthus reaction
What cells proliferate in Type IV hypersensitivity to mediate delayed-type hypersensitivity?
CD4+ T cells into TH1 and TH17 cells
What do TH1 cells secrete in delayed-type hypersensitivity?
Interferon-gamma to activate macrophages
What diseases are caused by T cell-mediated cytotoxicity in Type IV hypersensitivity?
Type I diabetes mellitus and multiple sclerosis
