Type III Hypersensitivity Flashcards
What is Type III hypersensitivity also known as?
Immune complex driven disease.
What are immune complexes?
Immune complexes are non-cell bound antigen-antibody complexes which are normally cleared through the activity of the immune system.
What happens if immune complexes cannot be efficiently cleared?
The immune complexes end up being deposited in the blood vessel walls and tissues, promoting inflammation and tissue damage.
When may an immune complex not be cleared properly?
As an example, if they are the result of antibodies reacting against self-antigens such as nuclear DNA.
What are some common symptoms caused by the body’s inability to clear the immune complexes?
Fever, rashes, joint pain or protein in the urine.
Many auto-immune diseases including rheumatoid arthritis, multiple sclerosis and systemic lupus erythematosus (SLE) involve type III reactions. What is SLE caused by?
In SLE patients develop IgGs against DNA or proteins present in the nucleus of cells (nucleoproteins), which form persistent immune-complex deposits and a variety of pathologies.
While many diseases associated with type III hypersensitivity are auto-immune in origin, as with all antibody-mediated diseases they can also result from encounters with foreign antigens. What are some examples of non-autoimmune causes of T3 hypersensitivity?
Persistent infection, such as hepatitis, can result in immune complexes being deposited.
Exposure to freely circulating antigens such as drugs can also cause a similar reaction.
What is serum sickness?
The type III hypersensitivity reaction resulting from repeated use of an anti-venom. This occurs as a result of our bodies forming antibodies against an anti-venom (e.g. for a snake bite) and then the next time we get bitten by that snake and need the anti-venom we get ill.
