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A panel-reactive antibody (PRA) is a group of antibodies in a test serum that are reactive against any of several known specific antigens in a panel of test leukocytes or purified HLA antigens from cells. It is an immunologic metric routinely performed by clinical laboratories on the blood of people awaiting organ transplantation. [1]
In immunology the particular macromolecule bound by an antibody is referred to as an antigen and the area on an antigen to which the antibody binds is called an epitope. In some cases, an immunoassay may use an antigen to detect for the presence of antibodies, which recognize that antigen, in a solution.
[1] [2] The diameter of the circle increases with time as the antigen diffuses into the medium, reacts with the antibody, and forms insoluble precipitin complexes. [ 1 ] [ 2 ] [ 5 ] The antigen is quantitated by measuring the diameter of the precipitin circle and comparing it with the diameters of precipitin circles formed by known quantities ...
The Ii antigen system is a human blood group system based upon a gene on chromosome 6 and consisting of the I antigen and the i antigen. [1] The I antigen is normally present on the cell membrane of red blood cells in all adults, while the i antigen is present in fetuses and newborns. [2]
A single antibody molecule has two antigen receptors and therefore contains twelve CDRs total. There are three CDR loops per variable domain in antibodies. Sixty CDRs can be found on a pentameric IgM molecule, which is composed of five antibodies and has increased avidity as a result of the collective affinity of all antigen-binding sites combined.
More recent, fourth-generation assays that assess for both the antibody and the antigen can have a window period as short as six weeks to detect more than 99% of infections, while third-generation tests that assess only for unbound antibody tend to have a longer window period of eight to nine weeks. [26]
Once set, light chain class remains fixed for the life of the B lymphocyte. In a healthy individual, the total kappa-to-lambda ratio is roughly 2:1 in serum (measuring intact whole antibodies) or 1:1.5 if measuring free light chains, with a highly divergent ratio indicative of neoplasm. The free light chain ratio ranges from 0.26 to 1.65. [1]
[1] The immunoglobulin heavy chain (IgH) is the large polypeptide subunit of an antibody (immunoglobulin). In human genome, the IgH gene loci are on chromosome 14. A typical antibody is composed of two immunoglobulin (Ig) heavy chains and two Ig light chains. Several different types of heavy chain exist that define the class or isotype of an ...