Download Type 1 -IgE Mediated Response

Type 1 -IgE Mediated Response
Mast cells (which lie near the skin, respiratory tract, GI tract, and mucous membranesplaces in the body exposed to environmental allergens) and basocells (which are blood
cells) release potent mediators of allergic reactions (histamine, acetylcholine). They do
this when allergens bind to the IgE antibodies for what is called the second exposure.
Granulation occurs on these subsequent exposures and that is when these inflammatory
mediators are released. On the first exposure to the allergen the desensitization and
granulation does not occur. Therefore mediators are not released.
Systemic Anaphylactic disorders
Examples of mediators/allergens
1. PCN
2. Radiocontrast dyes
3. Bee or wasp stings
4. Seafood
5. Nuts legumes
What you’ll see
 Bronchospasm
 Angiodema (swelling of then face)
 Massive vasodilatation- (circulatory shock)
Treat: Treat symptoms of airway constriction and circulatory collapse with epinephrine
for its B2 effects on airway, and vasoconstrictive effects on arterial system, and lots of
fluids for vascular space as well. Antihistamines (Benadryl)
Localized atopic disorders (high levels of IgE &
exquisitely reactive to mediators)
Examples of mediators/allergens
1. Allergic Rhinitis
2. Pollens
3. Ragweed
4. Grass/weeds
5. Spores
6. House dust mites
7. Animal dander
What you’ll see
 Nasal symptoms
 Sneezing, itching watery discharge from eyes
 Attacks accompanied by malaise and fatigue
 “Hay fever” seasonal
 Household allergen- worse at night
Treat: symptomatic relief, antihistamines, decongestants, intranasal corticosteroids
Food allergies:
Examples of mediators/allergens
1. Milk
2. Eggs
3. Peanuts
4. Soy
5. Tree nuts
6. Fish
7. Shellfish
What you’ll see
 Acute reaction=anaphylaxis
 Chronic reaction=asthma, atopic dermatitis, GI disorders
Diagnosis of food allergies requires a careful history, and “provacative diet testing”. This
means the suspected food needs to be eliminated from the diet for a period of time to see
if symptoms disappear. Then re-introduce foods to see if they reappear. One food is
tested at a time.
Treat: Avoidance of the food responsible for the allergy.
Type 11- Antibody Mediated Cytotoxic Disorders
Result of IgG and IgM class antibodies interacting with tissue/cell
surface antigens. Subsequent activation of “complement” or cellmediated cytotoxicity (the cell is doomed) occurs.
Examples:
1. Mismatched blood transfusions
2. Hemolytic disease of the newborn caused by ABO or Rh incompatibility
3. Certain drug reactions—The binding of the allergic drug to the surface of the RBC
or WBC elicits an antibody and complement response that lyses the drug coated
cell. POW! (Lytic drug reactions can produce anemia, leucopenia,
thromboctypenia)
What you may see
 Vasodilation
 Hypotension
 Flushing
 tachycardia.
You may also see:
 headache,
 chest pain
 chills
 pain or burning along the vein
 back pain
 fever
 dyspnea
Treat: Stop the transfusion!
Stop giving the drug!
Type 111 –Immune Complex Disorders
Immune complex disorders are mediated by the formation of antigen-antibody complexes
(immune complexes) that in turn activate complement. Activation of complement (which
causes release of Vasoactive mediators) causes tissue damage by altering blood flow,
increasing vascular permeability, and by the destructive action of inflammatory cells.
Immune complexes produce damage both in the vascular lining itself and the organs
where they may deposit (kidney, lung, joints) and causing an inflammatory response.
The harmful effects are indirect, secondary to the inflammatory response induced by
complement.
Examples of antigens that cause immune complex related injury:
1. Exogenous antigens- viral proteins and bacterial proteins
Acute glomerulonephritis that follows a streptococcal infection
2. Endogenous antigens- self antigens associated with autoimmune disorders
Systemic lupus erythematosus (SLE)
 Urticaria
 Patchy or generalized rash
 Extensive edema (face, neck, and joints)
 Fever
Damage can be temporary and resolve within a few days or prolonged and
continuous and lead to irreversible damage.
Type 1V Cell- Mediated Hypersensitivity
Occurs 24-72 hours after exposure to the offending antigen. It is mediated
by T-cells that are Cytotoxic and release inflammatory chemicals in the
surrounding tissue. These substances attract T or B lymphocytes. The
coagulation cascade is activated causing formation and deposition of
fibrin.
P.S. It is these Cytotoxic T-cells that that destroy cancer cells.
Examples:
1. Reaction to the tuberculin test
2. Allergic contact dermatitis
3. Latex allergy
4. Poison ivy
5. Transplant reaction
6. Crohn’s disease
Modulation of symptoms
 Corticosteroids
 Immunosuppressive drugs