PhD. student kefah F.Hasson 2014 Hypersensitivity Reactions type III.

PhD. student kefah F.Hasson2014

Hypersensitivity Reactions type III

Type III Reactions:

other name : Immune Complex .Involve reactions against soluble antigens circulating.

Usually involve IgA antibodies.

Antibody-Antigen immune complexes are deposited in organs, activate complement, and cause inflammatory damage.

Mechanism of type III hypersensitivity

Formation of the intermediate immune complex

Deposition of the intermediate immune complex

Tissue injury by the immune complex.

Immune Complex Mediated Hypersensitivity .

Common Disease of type III Hypersensitivity  

Arthus reaction : local immune complex reaction may cause Necrotic vasculitis, Ulcer.

1. Complement initiates mast cell degranulation

2. Neutrophils are chemotactically attracted to the site

3. Neutrophils release lytic enzyme after failed attempts to endocytose the immune complex

Serum Sickness  Disease: (SSD)

Acute systemic immune complex in tissue may cause fever, skin rash ,erhythema .

due to Penicillin 、 Sulfanilamide

Acute immune complex glomerulonephritis (locally) : due to Streptococcus infection .

Glomerulonephritis: Inflammatory kidney damage.Occurs with slightly high antigen-antibody ratio is present.

Serum sickness

Chronic immune complex disease Systemic Lupus Erythematosus (SLE):

Auto -antibodies react against DNA, blood cells, neurons, and other tissues. When cells die, immune complexes form and deposit under skin, joints, in kidneys, blood vessels, and central nervous system.

Rheumatoid Arthritis: auto -antibodies (rheumatoid factors) against IgG form complexes in joint, leading to inflammation and cartilage damage. Often causes finger and joint deformities.

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