This document discusses different types of hypersensitivity reactions. Type II reactions involve antibodies binding to antigens on cell surfaces and activating the complement system. Type III reactions, also known as immune complex reactions, occur when antibodies bind to antigens circulating in the bloodstream, forming immune complexes that can deposit in tissues and activate the complement system. Examples of Type III reactions provided are Systemic Lupus Erythematosus, Post-streptococcal Glomerulonephritis, and Drug Induced Serum Sickness. Type IV reactions are cell-mediated and involve activation of T lymphocytes.
12. Examples of Type III (Immune Complex) Hypersensitivity
Systemic Lupus Erythematosus : Antibodies are made that bind to certain nuclear
antigens which deposit mainly in the kidneys, skin, and joints.
Post-streptococcal Glomerulonephritis: While fighting a Streptococcal infection,
the patient makes antibody that reacts against the pathogen but also cross-react
with glomerular antigen which cause antigen-antibody complexes to lodge on
glomerular membrane.
Drug Induced Serum Sickness: Since most drugs are poor immunogens, they act
as a hapten by combining with tissue protein in the host and induce immune
responses against the drug-host protein complex.
Farmer’s Lung and Bird fancier’s disease: Pulmonary diseases resulting from
inhalation of bacterial spores and avian serum/fecal proteins respectively.
