Key Terms
Hypersensitivity reactions
Immune responses that cause damage rather than protection. Classified by mechanism, not severity.
Cytokines released
TNF-alpha 6. Collective mediator release causes symptoms
Timing
4-12 hours after early phase Cells involved: eosinophils, neutrophils, lymphocytes (recruited by chemotactic factors fro
Mechanism
Same as localized but widespread; involves kidneys, joints, blood vessels
Isohemagglutinins
IgM antibodies that cross-react with blood group antigens not present on an individual's own RBCs. Produced within first
Cause
Transfusion of ABO-incompatible blood Mechanism: recipient's isohemagglutinins bind to donor RBCs, agglutinate them, act
Symptoms
Fever, chills, pruritus, urticaria, dyspnea, hemoglobinuria, hypotension Severe outcome: shock, multi-organ failure, dea
Rh incompatibility in transfusion
First transfusion of Rh+ into Rh- person produces primary antibody response; HTR delayed up to 2 weeks. Second Rh+ trans
Cascade of inflammatory events
1. IgG binds antibody receptors on localized mast cells, triggering degranulation 2.
Arthus reaction
Localized; develops 3-10 hours after injection at injection site
Serum sickness
Systemic; immune complexes deposit throughout body
Sources
Animal antibodies used for passive immunity, certain drugs, microbial antigens from chronic infections (subacute bacteri
Autoimmune diseases with type III component
SLE, rheumatoid arthritis (auto-antibodies form immune complexes with self antigens).
Hypersensitivity Pneumonitis (HP)
Involves BOTH type III and type IV hypersensitivity; caused by inhaled dust, endospores, bird droppings, feathers, molds
Autoimmune disease
Immune system attacks the body's own cells due to loss of immune tolerance. Normal state: immune system maintains tolera