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Type I hypersensitivity
Autoimmune hemolytic anemia
Hemolytic disease of the newborn
Rheumatic heart disease
Type II hypersensitivity
Systemic lupus erythematosus
Type III hypersensitivity
Type IV hypersensitivity
Common variable immunodeficiency
Hyperimmunoglobulin E syndrome
IgG subclass deficiency
Isolated primary immunoglobulin M deficiency
Selective immunoglobulin A deficiency
Adenosine deaminase deficiency
Hyper IgM syndrome
Severe combined immunodeficiency
Cytomegalovirus infection after transplant (NORD)
Post-transplant lymphoproliferative disorders (NORD)
Chronic granulomatous disease
Leukocyte adhesion deficiency
Blood transfusion reactions and transplant rejection: Pathology review
Immunodeficiencies: Combined T-cell and B-cell disorders: Pathology review
Immunodeficiencies: Phagocyte and complement dysfunction: Pathology review
Immunodeficiencies: T-cell and B-cell disorders: Pathology review
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Hypersensitivity Type III
in type III hypersensitivity reactions p. 111
C3 deficiency and p. 105
organ transplants p. 117
Having a hypersensitivity means that someone’s immune system has reacted to something in a way that ends up damaging them, as opposed to protecting them.
There are four different hypersensitivities and the third type or type III hypersensitivity reaction happens when antigen-antibody complexes deposit in blood vessel walls, causing inflammation and tissue damage.
Alright so first off, type III hypersensitivity reactions are mediated by immune complexes. Immune complexes, aka antigen-antibody complexes are made of two parts—the antigen and the antibody.
Antibodies, sometimes called immunoglobulins, are produced by plasma cells, which are basically fully matured and differentiated B cells.
Initially these cells make IgM - which can be secreted or bound to the plasma cell surface where it acts as a B cell receptor.
When a B cell undergoes cross-linking of two surface bound IgMs, it then takes up the antigen and presents a piece of it to T helper cells via t cell receptor to the MHC- class II molecule presenting the piece of antigen, along with costimulatory molecule CD4.
The B cell’s CD40 also binds to the T cell’s CD40 ligand, and then the t cell releases cytokines, which results in b cell activation and class switching, or isotype switching, where it changes the type of antibodies it makes.
In type III hypersensitivity reactions, typically B cells will switch from making IgM to making IgG antibodies.
Type III hypersensitivity is a type of immune response in which antigen-antibody complexes accumulate in the tissues and cause inflammation and tissue damage. This type of hypersensitivity is also known as immune-complex-mediated hypersensitivity. Examples of Type III hypersensitivity reactions include systemic lupus erythematosus, rheumatoid arthritis, and serum sickness. Symptoms can vary depending on the tissues affected and may include joint pain and swelling, rashes, fever, and kidney damage. Treatment options may include removing the triggers, and medications like antihistamines, nonsteroidal anti-inflammatory drugs, and corticosteroids.
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