Allergy and Hypersensitivity Flashcards
What are the 4 types of hypersensitivity?
Type I: Allergy (histamines)
Type II: Antibody-mediated (transfusion reaction)
Type III: Immune Complexes (drug related)
Type IV: Delayed Type (contact dermatitis)
What antibody and receptor is responsible for Type I hypersensitivity?
IgE antibodies; FcER
Are atopic individuals more or less likely to be susceptible to allergens?
More susceptible because they produce IgE against common environmental antigens
What are the properties of allergens?
- nonparasitic
- many epitopes
- contain PAMPs to stimulate innate immunity
Describe the Type I reaction.
- Allergen comes into contact with IgM or IgG on naive B cell
- Th2 cell binds to naive B cell and releases IL-4 and IL-13 to cause class switch
- Class switch to IgE (now memory cell)
- Plasma cell secretes allergen-specific IgE
- IgE cross-link to Fc portion on FcER
- Upon second encounter, allergen binds to Fab portion of FcER
- Degranulation = acts on own tissues
What cells is FcER found on?
granulocytes
- eosinophils
- mast cells
- basophils
What granules are released from mast cells (basophils)?
histamines
Histamines induce…
- contraction of intestinal/bronchial smooth muscles
- increase vasopermeability
- mucous secretion
Name the second messengers of Type I.
Leukotrines and prostaglandins
- relay signals faster
- cause of asthma symptoms (tissue remodeling)
List the major cytokines and chemokines of Type I.
IL-4 and IL-13
- stimulate Th2 response and IgE production from B cells
IL-5
- recruits/activates eosinophils
TNF-a
- anaphylaxis
CXCL8
- chemokine
GM-CSF
- production/activation of myeloid cells
Early responses vs Late response of Type I.
Early: release of histamine, leukotrienes, prostaglandins (within minutes)
Late: influx of neutrophils, eosinophils, and Th2 cells
(within hours)
Systemic anaphylaxis is
-allergen system wide
- labored breathing, drop in blood pressure, bronchiolar constriction
treatment: epinephrine pen
Localized hypersensitivity reaction examples.
- hay fever
- eczema
- hives
- food allergies
treatment: anti-histamine
What antibodies are responsible for Type II.
IgG and IgM
How do antibodies induce cell death?
- Complement activation = MAC
- ADCC: NK cells recognize and lyse due to antibody binding to cancer cell
- Phagocytosis: antibody acts as opsonin (“tag”)
T/F. Adults posses natural antibodies for blood group they do NOT have.
True
What occurs is Type A blood recieves donor blood from Type B.
Anti-B antibodies from Type A blood will attack Type B blood causing cytolysis and hemagglutination.
List the blood type and their serum antibodies.
Type A = Anti-B
Type B = Anti-A
Type AB = none
Type O = Anti-A and Anti-B
Hemolytic Disease of the newborn is when which antibody crosses the placenta?
IgG
In order to develop hemolytic disease of the newborn, which Rh factor does the mother possess?
Rh (-)
What is Type III response usually due to?
anything drug-related due to immune complexes depositing in tissues and antigen not completely going away
List some symptoms of Type III.
- Blood vessel: vasculitis
- Kidney: glomerulonephritis
- Joints: arthritis
- fever
- rashes
Describe Arthus reaction.
- inflammation induced by injection of antigen with highly circulating antibody (4-10 hours after injection)
Type IV hypersensitivity is initiated by which cells?
T-cells and recruitment of macrophages to site of inflammation
DTH reaction sensitization phase…
- initial exposure triggers T-cell response (Th1)
- takes 1-2 weeks
DTH reaction effector phase…
- second exposure to sensitizing antigen
- production of Th1 inflammatory cytokines (IFN-g)
List the reactions of DTH.
- contact dermatitis
- rashes and blistering lesions
- chemical/cosmetic rashes
List the hypersensitivity Type, the immune mediator(s), mechanism of reaction, and manifestation reactions (time).
