Hypersensitivity from the P4 Student not me Flashcards
What is hypersensitivity
Hyperactive immune responses against “harmless” antigens
auto-immunity
Type of hypersensitivity that is caused by a breakdown in the mechanisms that normally ensure tolerance of self
What is the most common type of hypersensitivity
Type 1 (the allergic response)
What individuals are predisposed to having a type 1 hypersensitivity reaction
atopic indviduals
What type of antibodies recognize the allergen
IgE
What type of cell does the IgE antibody bind to, what part of the antibody binds
Mast cell, Fc
Where are mast cells found
Mucosa
T/F: An allergen will cross link IgE on mast cells triggering degranulation
True
What occurs when mast cells degranulate
allergy symptoms from mediators, recruitment of basophils from blood
What occurs in the late phase of type 1 hypersensitivty
mediators recuit other inflammatory cells (eosinophils and neutrophils)
What are the mediators of type 1 hypersensitvity
Histamine, prostaglandins, leukotrienes, TNF-alpha and IL-4
What does the mediator histamine cause
vasodilation, increased capillary permeability, smooth muscle contraction (bronchospasm)
What does the mediator prostaglandins cause
bronchoconstriction, attract white blood cells
What does the mediator leukotrienes cause
Capillary permeability (longer duration)
What do the mediators TNF-alpha and IL-4 do
inflammation, cytokine release that stimulates T helper 2 cells
What is an allergen
small inhaled proteins that stimulate IgE production in atopic individuals
What makes an effective allergen
small and highly soluble, low dose, carried on dry a particles
What is the difference in antibody production in non-atopic and atopic individuals
atopic individuals produce IgE, non-atopic individuals produce IgG
T/F: Atopic individuals have more Th1 allergen specific cells
False: Atopic individauls have more Th2 allergen-specific cells
How do Tregs create a bias towards T helper 2
Atopic individuals have defective Tregs in supressing T helper 2 cytokine production
What the theories that as to how atopic indviduals have T helper 2 bias
Th2 bias developed as a fetus, lack of childhood infection may maintian T helper 2 bias, genetic predisposition toward allergic response, lack T reg response to allergen
How does specific immunotherapy work
injection of gradually increasing doses of allergen causing either T helper differentiation towards 1 or IgG:IgE increases 100 fold
What occurs in type 2 hypersensitivity (cytotoxic)
Antigens on a cell surface combine with antibody
What are the three ways type 2 toxicity cause cell damage
complement, Ab-Ag induced cell dysfunction, complement activation attracts PMN to site causing phagocytosis
