Hypersensitivity Reactions and Transplant Rejection EC Flashcards Preview

Evan's Step 1 Prep Material > Hypersensitivity Reactions and Transplant Rejection EC > Flashcards

Flashcards in Hypersensitivity Reactions and Transplant Rejection EC Deck (12):

Type I Hypersensitivity

Antigen cross links IgE on sensitized mast cell--> Histamine
Rapid response with preformed antibody
"Wheel and flair" reaction


Type II Hypersensitivity

Cytotoxic (antibody mediated) - IgM, IgG bind fixed antigen which leads to cellular destruction
~opsonization w/ phagocytosis
~complement activation and lysis
~Antibody mediated killing via NK cells


Type III Hypersensitivity

IgG immune complexes deposit

Serum sickness- Immune complexes deposit in membranes where they fix complement

Arthus reaction- Intradermal injection of antigen leads to deposition of complexes in the skin (edema necrosis, complement activation)


Type IV Hypersensitivity

Delayed (T-Cell mediated)
Sensitized T-Lymphocytes recognize antigen and release lymphokines


Examples and Presentation of Type I Hypersensitivity

Anaphylaxis (bee sting, food/drug allergies)
Allergic/atopic disorders (rhinitis, hay fever, eczema, hives, asthma)

Immediate anaphylactic


Examples and Presentation of Type II Hypersensitivity

Autoimmune hemolytic anemia, Pernicious anemia, ITP, Erythroblastosis fetalis (Rh mismatch w/ mother), Acute hemolytic transfusion reactions, Rheumatic fever, Goodpasture's, Bullous pemphigoid, Pemphigus vulgaris

Specific to tissue or site where antigen is found (local)


Examples and Presentation of Type III Hypersensitivity

SLE, Polyarteritis nodosa, Poststrep. glomerulonephritis, Serum sickness, Arthus reaction

Vasculitis and systemic manifestations


Examples and Presentation of Type IV Hypersensitivity

MS, Guillain-Barre, GVH, PPD, Contact dermatitis (poison ivy, Nickel allergy)

Response is delayed and does NOT involve antibodies (T-Cell mediated)


Rejection of transplant within minutes with occlusion of graft vessels causing ischemia and necrosis.

Hyperacute graft rejection

Antibody mediated (type II)
Presence of preformed anti-donor antibodies


Rejection of transplant weeks later with vasculitis of graft vessels with dense interstitial lymphocytic infiltrate.

Acute graft rejection

Cytotoxic T-cell reaction to foreign MHC
Reversible with immunosuppressants


Rejection of transplant months to years later. Irreversible T-cell and antibody mediated vascular damage.

Chronic graft rejection

Class-I MHC(nonself) is perceived by CD8 cells as self presenting non-self antigen.


Maculopapular rash, jaundice, hepatosplenomegaly, diarrhea following transplant.

GVH disease

Grafted immunocompetent T cells proliferate and reject foreign (host) cells. Severe organ dysfunction.

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