Hypersensitivity Reactions and Transplant Rejection EC Flashcards
Type I Hypersensitivity
Anaphylactic/atopic
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.
