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Immunology
Allergy and Hypersensitivity
47
Medical
Post-Graduate
03/01/2009

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Cards

Term

Four types of hypersensitivity

Definition
  • type I- allergic
  • type II- cytotoxic
  • type III- immune complex
  • type IV- cell mediated
Term

Examples of type I allergic reactions

Definition
  • asthma
  • eczema
  • hives/urticaria
  • food allergies

MOST EXTREME IS ANAPHYLAXIS!!!!!!!!

Term
Mechanism of sensitization in allergic reaction
Definition
  1. Th2 cells respond to specific antigen
  2. primed Th2 cells secrete IL-4
    1. cause isotype switching in B cell to produce IgE
  3. IgE binds to high affinity FcεRI on mast cells and basophils
  4. results in sensitized mast cells and basophils that can be triggered very quickly
Term
Mechansim of effector phase of allergic reaction
Definition
  1. subsequent allergen exposure cause cross- linking of igE on tissue mast cells and basophils
  2. degranuation of mast cells, basophils in two ways
    1. immediate phase- release contents of preformed granules
    2. late phase- release newly synthesized mediators
Term
Contents of preformed granules within mast cells and basophils involved in type I rxns
Definition
  • histamine
  • heparin (anticoagulant)
  • chemotactic factors (attract neutrophils, eosinophils)
  • trypase (cleave peptides, activate remodeling)
Term
Effect of histamine release
Definition
  • increase muscle contraction (bronchoconstriction)
  • increase vascular permeability
    • rapid fluid movement
    • increase secretion by nasal, bronchial, gastric glands
Term
Clinical manifestations of histamine release
Definition
  • hives (from dermal vasodilation, vessel permeability)
  • bronchospasm in lung
  • rhinnorhea
Term
Contents released during the late phase of effector phase type I hypersensitivity
Definition
  • leukotrines
  • platelet activating factor (PAF)
  • prostaglindins
  • cytokines
    • TNF-α
    • IL-5
Term
Function and clinical effects of leukotrine
Definition
  • function- prolonged constriction of smooth muscle and vascular permeability
  • clinical effects- continued bronchial hyperresponsiveness → asthma
Term

Fuction of Platelet activating factor

Definition
  • aggregation of platelets
  • bronchoconstriction
Term
PG's produced by mast cells/basophils and their effects
Definition
  • PGD2- increase vascular permeability and smooth muscle contraction(increase airway reactivity)
  • PGE2- increase vascular permeability and increase pain
Term
Function of cytokines
Definition
  • TNF alpha- induce local inflammation by upregulating endothelial expression of leukocyte adhesion molecules
  • IL-5- promote production of eosinophils by bone marrow
Term
Role of eosinophils in type I hypersensitivity
Definition
  • release cationic granule protines
  • release enzymes
    • eosinophil peroxidase → tissue remodeling
Term
What caues chronic allergic conditions such as asthma and eczema?
Definition
  • result of persistant tissue inflammation due to persistant leukocyte recruitment and activation
Term
Cause of anaphylaxis
Definition
allergen triggers mast cell degranulation in many systemic organs simultaneously
Term

Process of anaphylaxis

Definition
  • bronchoconstiction due to lung swelling (thromboxanes, PAF)
  • asphyxiation due to swelling of throught
  • systemic shock due to massive drop in bp (increase vasodilation, vascular permeability via PG's, NO) associated with fluid mobility
  • vomit
  • elevated HR to attempt to compensate
Term

Treatment for allergic reactions

Definition
  • avoid allergen
  • antihistamine
  • antileukotrine
  • desensitization
  • allergy shots (IgE to IgG shift)
Term
Mechanism of action of antihistamines
Definition
block H1 and H2 receptors on smooth muscle cells, blood vessles, and in the nose
Term
Mechanism of action of Singulair/Montelukast
Definition
block leukotrine receptors
Term
Clinical symptoms of asthma
Definition

shortness of breath

coughing

wheezing

Term
Histopathological features of asthma
Definition
  • excess mucus secretion
  • submucosal anti-inflammatory infiltrate with lymphocytes and eosinophils
  • smooth muscle cell hyperplasia
  • thick basement membrane
Term
Mechanism of action of allergy shots to treat type I hypersensitivity
Definition
  • exposure to increasing amounts of allergen induce shift from Th2 to Th1 priming
  • the goal is to trick the body into thinking the allergen is a part of oneself and to stop mounting an allergic response to it
  • it will result in body becoming tolerant to it and making more Th1 IgG immune response to allergen rather than IgE response
Term
Mechansim of action of desensitization in type I hypersensitivity reactions
Definition
  • expose to increasin amounts of allergen
  • induce desensitization or exhaustion of allergen-specific T cells and B cells
Term
Define type II hypersensitivity/cytotoxic rxns
Definition
Ab (IgG) mediated so Ab's are made against cells
Term
How do Ab's cause damage to body in type II hypersensitivity
Definition
  • opsonize cells and activate complement cascade
  • recruit neutrophils, macrophages that cause tissue damage
  • Ab's bind to normal cell receptors and interfere with their function
Term
Clinical diseases caused by type II hypersensitivity
Definition
  • Grave's disease
  • Myasthenia gravis
  • Goodpasture's disease
  • thrombocytopenia
  • type II diabetes
  • acute rhematic fever
Term
Cause, clinical signs of Graves disease
Definition
  • cause- antibody is anti-TSH receptor
  • clincal symptoms
    • hyperthyroidism
    • "bulging eyes"
    • enlarged thyroid
    • heat intolerance
    • palpitations
    • weight loss
Term
Cause, clinical symptoms of myasthenia gravis
Definition
  • cause- Ab against ACh receptor which keeps ACh from binding
  • clinical symptoms
    • muscle weakness
    • droopy eyes
    • paralysis
Term

Cause and clinical signs of Goodpasture's disease

Definition
  • cause- Ab's against basement membrane of the alveoli in lung and kidneys
  • clinical symptoms
    • nephritis
    • lung hemorage
    • on path slide: Ab deposits
Term
Cause of drug induced anemia/thrombocytopenia
Definition
  • drugs bind to RBC and platelets
  • Ab generated against drug will bind to host cells and induce their killing
Term
Cause of erythroblastosis fetalis
Definition
  • mother is Rh neg and first child is Rh positive, leading to her buidling up IgG's to the child
  • upon the second pregnancy, if she has a Rh positive child, her Ab's cross the placenta and react with fetal RBC's leading to hemolytic anemia
Term
Treatment of erythroblastosis fetalis
Definition
give Rhogam (antiRh IgD Ab) at 28 wks and 72 hours before birth (also given after abortion)
Term

Process of type III hypersensitivity

Definition
  1. Ag:Ab conmplexes bind FcγRIII on tissue mast cells
  2. release proinflammatory factors
  3. recruit macrophages, neutrophils to tissue site
Term
Examples of type III hypersensitivity diseases
Definition
  • lupus
  • rheumatoid arthritis
  • serum sickness
  • post streptococcal glomerular nephritis
Term
Two main types of type III hypersensitivities
Definition
  • local (arthus rxn)- in skin following vaccine or local infection
  • systemic (serum sickness)- example is anti-venom antidote, anti-venom, anti-lymphocyte (treatment: stop drug)
Term
clinical symptoms of systemic type III hypersensitivities
Definition
  • fever
  • swollen lymph nodes
  • painful and swollen joints
  • rashes
Term
Cause and symptoms of lupus
Definition
  • cause- Ag is dsDNA, other nuclear proteins, Smith
  • clinical symptoms
    • butterfly facial rash
    • vasculitis
    • nephritis
    • arthritis
Term
Cause and symptoms of arthritis
Definition
  • cause- cross rxn of Fc portion of IgM, IgG
  • symptoms- painful, swollen joints
Term
Clinical symptoms of serum sickness
Definition
  • fever
  • rash
  • vasculitis
  • arthralgias
Term
cause and clinical signs of streptococcal glomerulonephritis
Definition
  • streptococcal cell wall Ag's deposit into glomerular basement membrane
  • show as nephritis and bumpy lumpy deposits
Term

Different forms of Type IV hypersensitivity

Definition
  • delayed type
  • contact
Term
Process of delayed type hypersensitivity and example
Definition
  • Th1 cells stimulated by antigen loaded macrophages
  • Th1 activate macrophages to secrete proinflammatory facdtors, leading to local tissue inflammation

Ex: PPD TB skin test

Term

Process of contact hypersensitivity

Definition
  • CD4 mediated
    1. small reactive molecules (ex: metals) form hapten complexes with host proteins
    2. complexes taken up by APC and presented with MHC II to stimulate Th1 cells
    3. Th1 cells secrete IFNγ and TNF to activate macrophages
  • CD8 mediated (most common: poison ivy)
    1. chemical cross into cytoplasm of host cells and modify host proteins so they appear forein
    2. these proteins presented to surface of host cell with MHC I
    3. CD8 cells stimulated to kill these "foreign looking" cells
Term
Clinical pathologies/disease of type IV hypersensitivity
Definition
  • IDDM
  • Multiple schlerosis
  • contact dermititis
Term
Cause and symptoms of MS
Definition
  • cause- Ag is myelin basic protein
  • symptoms
    • progressive demyelination
    • blurred vision
    • paralysis
Term
Cause and symptoms of contact dermititis
Definition
  • cause- Ag could be nickel, poison ivy
  • symptoms
    • rash
    • vesicles
    • itchiness
Term
Cause of IDDM
Definition
Ag to pancreatic beta cells, Glu decarboxylase
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