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18 Cards in this Set

  • Front
  • Back
What is Type 1 hypersensitivity
Immediate hypersensitivity: IgE antibody mediated
What is type 2 hypersensitivity
Antibody-mediated: IgG anti-tissue antibody mediated
What is type 3 hypersensitivity
Immune complex-mediated: IgM/IgG antibody-mediated complexes
What is type 4 hypersensitivity
Delayed-type hypersensitivity: T cell mediated (CD4 and CD8)
What type of hypersensitivity is seen in allergic reactions
Type 1 IgE mediated; allergy and anaphylaxis
What are the steps in the synthesis of IgE and sensitization step (primary antibody response)
1. Dendritic cells are primary APC
2. Naive CD4 T cells develop into Th2 cells in association with MHC II
3. Th2 cells secrete IL-4 which promotes class switching to IgE. Memory B cells are produced
4. IgE binds to mast cells (FceRI receptor)
What is the memory response in the allergic response
1. Memory B cells have surface IgM that binds antigen
2. Th2 cells recognize these B cells, and secrete IL-4
3. B cells differentiate into plasma cells and secrete IgE, which binds to mast cells
4. Eosinophils and basophils also release preformed toxic molecules, as well as cytokines and inflammatory mediators
What are the effects of IgE mediated allergic reactions
1. Systemic anaphylaxis: vascular engorgement and asphyxia secondary to bronchial and larygeal constriction (1 hr duration)
2. Cutaneous anaphylaxis: Transient redness and swelling for 30 minutes
What happens in the wheal and flare reaction
There is an immediate reaction caused by IgE mediated mast cell degranulation. There is also a late phase reaction 6-8 after exposure, due to the leukotrienes and cytokines synthesized by IgE mediated activation of mast cells
What are Rhinitis and asthma caused by
Inhaled allergens
What are urticaria, angioedema, and eczema reactions to
Allergic reactions in the skin
What is Atopy
Exaggerated tendency to mount IgE responses to a wide variety of environmental allergens. Influenced by several genetic factors
What are four major environmental factors that contribute to atopy
1. Changes in exposure to infectious diseases in early childhood
2. Environmental pollution
3. Dietary changes
4. Allergen levels
What are some examples of Type 2 hypersensitivity reactions
Transfusion reactions, Hemolytic disease of the newborn, drug-induced hemolytic anemia
What are some mechanisms by which antibodies against tissue antigens cause disease
1. Opsonization and phagocytosis (hemolytic disease of the newborn, transfusion reactions)
2. C' and FcR-mediated inflammation and tissue injury (ab-mediated glomerulonephritis)
3. Abnormal responses without cell or tissue injury (Graves disease or Myasthenia gravis)
What causes type 3 hypersensitivity reactions
Deposition of immune complexes in blood vessels (systemic lupus erythematosis)
What type of cell causes type 4 hypersensitivity
T cell
What are the mechanisms of T cell-mediated hypersensitivity reactions
1. CD4 Th1 cells are sensitized. Upon subsequent exposure, they activate macrophages
2. CD8 CTL causes cytolysis