Type III and IV Hypersensitivities

Type III Hypersensitivities are driven by

accumulation of immune complexes

The accumulation of immune complexes results in

inflammatory response, attraction of leukocytes

Type III Time frame

4-6 Hours

Type III Hypersensitivities Phase I (Sensitization)

Self (Autoimmunity) or Foreign Ag causes formation of Ab

Type III Hypersensitivities Phase II (Pathology)

Subsequent exposure to Ag, Ab binding, formation of immune complexes

inefficient clearing leads to

aggregate into large numbers, tissue damage

When immune complexes deposit in tissue (3)

Trigger inflammatory or vasoactive mediators, induce protease-mediated connective tissue damage, form clot

Triggers inflammatory or vasoactive mediators for

Leukocyte trafficking

Arthus Reaction symptoms

Swelling, localized bleeding, Redness

form clot via

platelet activation

Arthus Reaction may develop after

Type I hypersensitivity to insect bite, DPT vaccine, Inhalation of Ag

Injecting ____ into individual with high levels of ____s will result in formation of ____, leading to ___

ag, anti-Ag Abs, Immune Complexes, exacerbated inflammatory

Discovered in 1903 after Arthus repeatedly injected

horse serum into rabbits

Discovered in 1903 after Arthus repeatedly injected horse serum into rabbits and observed symptoms of

edema and gangrene

Arthus reaction site of immunecomplex deposition

perivascular area

Farmer’s lung site of immunecomplex deposition

alveolar/capillary interface

Arthritis site of immunecomplex deposition

Joint Spaces

Arthus reaction route

subcutaneous

Farmer’s lung route

inhaled

Arthritis route

intravenous (high dose)

Vasculitis site of immune complex deposition

blood vessel walls

Type IV Hypersensitivities mediated by

T cells and macrophages

Type IV Hypersensitivities time frame

1-3 days

It is the delayed-type hypersensitivity because it takes a bit of time for the

TH1 cell to recognize the Ag and begin proliferating