Post on 30-May-2018
8/14/2019 Type III Hypersensitivity santos.pptx
1/13
Type III Hypersensitivity
8/14/2019 Type III Hypersensitivity santos.pptx
2/13
Type III HypersensitivityType III Hypersensitivity The formation of immune complexes through
the combination of antibody with antigen is the
first step in many immunological processes. One ofthe most significant of these processes is thecomplement cascade. When complement-activating immune complexes are deposited intissues, chemotactic factors are produced and leadto a local accumulation of neutrophils. These
neutrophils release their lysosomal emzymes andoxidizing radicals, and these in turn cause localtissue destruction. Lesions generated in thisfashion are called type III, or immune complex-mediated, hypersensitivity reaction.
8/14/2019 Type III Hypersensitivity santos.pptx
3/13
TYPE OF IMMUNE-COMPLEX DISEASETYPE OF IMMUNE-COMPLEX DISEASE
The combined effects of a low-grade persistentinfection and a weak antibody response lead to
chronic immune-complex formation, andeventual deposition of complexes in the tissues.
8/14/2019 Type III Hypersensitivity santos.pptx
4/13
Autoimmune disease Immune-complex disease is a frequent
complication of autoimmune disease, where the
continued production of autoantibody to a self-antigen leads to prolonged immune complexformation. As the number of complexes in the blood increases, the systems that are
responsible for the removal of complexes( mononuclear phagocyte, erythrocyte andcomplement) become overloaded, andcomplexes are deposited in the tissues.
8/14/2019 Type III Hypersensitivity santos.pptx
5/13
Inhalation of Antigenic Material Immune complexes may be formed at body
surfaces following exposure to extrinsic
antigens. Such reactions are seen in the lungsfollowing repeated inhalation of antigenicmaterials from moulds, plants and animals.
8/14/2019 Type III Hypersensitivity santos.pptx
6/13
Cause Antigen Site of complexdeposition
PersistentInfection
MicrobialAntigen
Infected organs,Kidney
Autoimmunity Self antigen Kidney, joint,arteries, skin
InhaledAntigen
Mould, plants oranimal antigen
Lung
8/14/2019 Type III Hypersensitivity santos.pptx
7/13
MECHANISM IN TYPE III HYPERSENSITIVITYMECHANISM IN TYPE III HYPERSENSITIVITY
Immune complexes are capable of triggering a wide variety ofinflammatory processes:
Complexes interact directly with basophils and platelets to induce the release of vasoactive amines.
Macrophages are stimulated to release cytokines, particularly TNFa
and IL-1, that are very important during inflammation.
They interact with the complement system to generate C3b and C5a
(anaphylatoxins). These complement fragments stimulate therelease of vasoactive amines (including histamine and 5-hydroxytryptamine) and chemotactic factors from mast cells andbasophils. C5a is also chemotactic for basophils, eosinophils, and
neutrophils.
8/14/2019 Type III Hypersensitivity santos.pptx
8/13
8/14/2019 Type III Hypersensitivity santos.pptx
9/13
CLASSIFICATION OF TYPE III HYPRSENSITIVITY
The severity and significance of type IIIhypersensitivity reactions depend on the
amount and site of deposition of immunecomplexes.
8/14/2019 Type III Hypersensitivity santos.pptx
10/13
TWO MAJOR TYPE OF REACTION ARE RECOGNIZEDTWO MAJOR TYPE OF REACTION ARE RECOGNIZED
1. LOCAL TYPE HYPERSENSITIVITY REACTIONS(ARTHUS REACTION)
Named after the biologist who first described it. Thearthus reaction occurs when immune complexes aredeposited in tissues.
8/14/2019 Type III Hypersensitivity santos.pptx
11/13
Antigen injected intradermally orsubcutaneously combines withspecific antibody from the
blood to form immunecomplexes. The complexes acton platelets and mast cells,
which release vasoamines.Immune complexes alsoinduce macrophages to releaseTNF and IL-1. mast cell
products, including histaminesand leukotrienes, inducedincreased blood flow andcapillary permeability. Theinflammatory reaction ispotentiated by lysosomalenzymes released from thepolymorphs. The Arthusreaction can be seen inpatients with precipitatingantibodies, such as those withextrinsic allergic alveolitisassociated with Farmers lung
disease.
8/14/2019 Type III Hypersensitivity santos.pptx
12/13
2. GENERALIZED TYPE HYPERSENSITIVITY2. GENERALIZED TYPE HYPERSENSITIVITY When large amount of antigen enter the
bloodstream and bind to antibody, circulatingimmune complexes can form. If antigen is inaccess, small complexes form; because these arenot easily cleared by the phagocytic cells, theycan cause tissue-damaging type III reactions atvarious sites.
8/14/2019 Type III Hypersensitivity santos.pptx
13/13
Human diseases associated withType III hypersensitivity
vBacterial diseases Streptococcal
Mycoplasma pneomunia Leprosy SyphilisvViral diseases Infectious mononucleosis Hepatitis
Dengue hemorrhagicvParasitic diseases Malaria Leishmaniasis Schistosomiasis Onchocerciasis
vvTumors
vAutoimmune diseases Rheumatoid arthritis Systemic lupus
erythematosus Autoimmune thyroiditis
vOthers Serum sickness Hypersensitivity
pneumonitis IgA nephropathy