Complement
This activates the lectin pathway of complement.
What is mannose-binding lectin (MBL)?
This pathway is primarily activated by antigen-antibody complexes.
What is the classical pathway?
Arthus reaction, a skin reaction of localized inflammation characterized by redness and edema that peaks 3-8 hours after exposure, is typical of this type of hypersensitivity reaction.
What is type III hypersensitivity reaction?
The immune mechanism for this type of reaction is the release of mediators from IgE-sensitized mast cells and basophils.
What is type I hypersensitivity?
The immune mechanism for this reaction is that cell destruction is caused by antibody to bound-antigen and complement, opsonization, or ADCC. Cell function can be inhibited or stimulated by antibody binding.
What is type II hypersensitivity?
This protein is found in the alternative pathway of complement and stabilizes the C3 convertase (C3bBb), therefore extending its half-life.
What is properdin?
Lysis of foreign cells
Increase in vascular permeability
Migration of neutrophils to the tissues
What are the functions of the complement system?
The immune mechanism for this reaction is that antibody-soluble antigen complexes activate complement proteins. Neutrophils are recruited and release lysosomal enzymes that cause tissue damage.
What is a type III hypersensitivity reaction?
This reaction, typical of type IV hypersensitivity, usually develops 24-48 hours after antigen exposure.
What is a delayed hypersensitivity reaction?
Patch test, skin testing, the Mantoux test, and Interferon gamma release assays (IGRA) all test for this type of hypersensitivity.
What is type IV?
This protein inhibits complement by dissociating C1r and Cs from C1q. Lack of this protein causes a disease called Hereditary angioedema.
What is C1 inhibitor?
The recognition unit of the classical complement pathway.
What is C1qrs?
These hypersensitivity categories are considered immediate reactions due to developing minutes to hours after antigen exposure.
What are type I, type II, and type III hypersensitivity reactions?
This test detects RBCs coated with complement or IgG antibody in vivo. Patient RBCs are incubated with a poly-specific anti-human immunoglobulin directed against IgG and complement (C3). If positive, repeat testing with mono-specific anti-IgG, anti-C3b, and anti-C3d.
What is a direct antiglobulin test (DAT)?
The immune mechanism for this type of reaction is that antigen-sensitized Th1 cells release cytokines that recruit macrophages and induce inflammation or activate Tc cells to cause direct cell damage.
What is type IV hypersensitivity?
C3bBbPC3b
What is the C5 convertase (activation unit) of the alternative pathway?
This is a cofactor with Factor I. It results in cleavage of C3b into an enzymatically deactivated iC3b.
What is factor H?
This is a generalized reaction caused by passive immunization of humans with animal serum creating antibodies against the foreign animal protein. Causes complexes to form and deposit into tissues. Symptoms include fever, headache, nausea, joint pain, rashes, and lymphadenopathy.
What is serum sickness?
Key components for this type of hypersensitivity reaction are IgE, mast cells, basophils, and eosinophils.
What is a type I hypersensitivity reaction?
What are clinical examples of type I hypersensitivity reactions?
CH50 is an assay to detect components C1-C9 of the classical pathway. This assay is used to detect the multiple components of the alternative pathway.
What is AH50?
This assay measures the amount of patient serum required to lyse 50% of a standardized concentration of antibody-sensitized sheep erythrocytes.
What is the hemolytic titration (CH50) assay?
IgE binds to this receptor on mast cells and basophils.
What is FcεR1?
This is believed to induce immune tolerance to an allergen by shifting the immune response to a Th1 type response, inducing the development of Treg cells, and inducing the production of IgG4 antibodies that block binding of the allergen to IgE.
What is allergy immunotherapy (AIT) or allergy shots?
Transfusion reactions, autoimmune hemolytic anemia, anti-GBM disease, Hashimoto's disease, and hemolytic disease of the newborn (HDN).
What are clinical examples of type II hypersensitivity reactions?