Hypersensitivity Reactions Immunology Review 387
TYPE I: TYPE II: TYPE III: IMMUNE TYPE IV: T-CELL
ANAPHYLACTIC CYTOTOXIC COMPLEX DEPENDENT
Key reactant(s)
Mechanism
Onset of
symptoms
Examples
T cells
Release of cytokines
Delayed (sensitization after
1st contact with ag, symp-
toms upon reexposure).
Contact dermatitis, hypersen-
sitivity pneumonitis, tuber-
culin skin test
IgG, IgM, complement,
soluble antigens
Deposits of ag-ab com-
plexes in tissues
Immediate
Arthus rxn, serum sick-
ness, systemic lupus
erythematosus (SLE),
rheumatoid arthritis (RA)
IgE
Release of mediators
from mast cells &
basophils
Immediate
Anaphylaxis, hay
fever, asthma, food
allergies
IgG, IgM, complement,
cellular antigens
Cytolysis due to ab &
complement
Immediate
Transfusion reactions,
hemolytic disease of
newborn, autoimmune
hemolytic anemia