A<unk>  <unk>  is a group of antibodies in a test serum that are<unk>  against any of several known specific antigens in a<unk>  of test cells or purified HLA antigens from cells. It is an immunologic test routinely performed by clinical laboratories on the blood of people awaiting organ transplantation. In this test recipient cells are exposed to random cells of donor population and estimation risk of acute rejection. The<unk>  score is expressed as a percentage between 0% and 100%. It represents the proportion of the population to which the person being tested will react via pre-existing antibodies against human cell surface antigens,HLA and other polymorphic antigen systems. A<unk>  score greater than 6 is in danger, and over 20 requires a desensitization process, but its intensity varies. These antibodies target the surface antigens of target cells, such as HLAs. In other words, it is a test of the degree of alloimmunity in a graft recipient and thus a test that quantifies the risk of transplant rejection. Each population has a different demographic prevalence of particular antigens, so the<unk>  test<unk>  constituents differ from country to country. A traditional<unk>  test is performed using a<unk>  of lymphocytes from potential donor population. Since late 1990s, a purified HLA antigen<unk>  has been used to replace a cell<unk>  for the<unk>  test, based on the assumption that HLA is the major target antigen system of alloantibody reaction. However, the non-HLA antibody effect on the<unk>  test has been ignored. (ref:Human leukocyte antigen antibodies for monitoring transplant patients. Surg Today. 2005;35(8):605-12.) A high<unk>  value usually means that the individual is primed to react immunologically against a large proportion of the population. Individuals with a high<unk>  value are often termed "sensitized", which indicates that they have been exposed to "foreign" (or "non-self") proteins in the past and have developed antibodies to them. These antibodies develop following previous transplants, blood transfusions and pregnancy. Transplanting organs into recipients who are "sensitized" to the organs significantly increases the risk of rejection, resulting in higher immunosuppressant requirement and shorter transplant survival. People with high<unk>  scores therefore wait longer for an organ to which they have no pre-existing antibodies. Extensive efforts have been made to identify treatment regimes to reduce<unk>  in sensitized transplant candidates. In certain circumstances, plasma exchange, intravenous immunoglobulin, rituximab and other "antibody-directed" immune therapies may be employed, but this is an area in which active investigation continues.
Panel-reactive antibody
Cold sensitive antibodies
Heterophile antibody
Donor-specific antibody
Mixed-field agglutination
Isoantibodies
Strain pattern
Neutralizing antibody