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An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein produced mainly by plasma cells that is used by the immune system to neutralize pathogens such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the pathogen, called an antigen, via the fragment antigen-binding (Fab) variable region. Each tip of the "Y" of an antibody contains a paratope that is specific for one particular epitope on an antigen, allowing these two structures to bind together with precision. Using this binding mechanism, an antibody can tag a microbe or an infected cell for attack by other parts of the immune system, or can neutralize its target directly. Depending on the antigen, the binding may impede the biological process causing the disease or may activate macrophages to destroy the foreign substance. The ability of an antibody to communicate with the other components of the immune system is mediated via its Fc region, which contains a conserved glycosylation site involved in these interactions. The production of antibodies is the main function of the humoral immune system.
A blood type is a classification of blood, based on the presence and absence of antibodies and inherited antigenic substances on the surface of red blood cells (RBCs). These antigens may be proteins, carbohydrates, glycoproteins, or glycolipids, depending on the blood group system. Some of these antigens are also present on the surface of other types of cells of various tissues. Several of these red blood cell surface antigens can stem from one allele and collectively form a blood group system.
In biology, immunity is the balanced state of multicellular organisms having adequate biological defenses to fight infection, disease, or other unwanted biological invasion, while having adequate tolerance to avoid allergy, and autoimmune diseases.
Humoral immunity or humoural immunity is the aspect of immunity that is mediated by macromolecules found in extracellular fluids such as secreted antibodies, complement proteins, and certain antimicrobial peptides. Humoral immunity is so named because it involves substances found in the humors, or body fluids. It contrasts with cell-mediated immunity. Its aspects involving antibodies are often called antibody-mediated immunity.
Transplant rejection occurs when transplanted tissue is rejected by the recipient's immune system, which destroys the transplanted tissue. Transplant rejection can be lessened by determining the molecular similitude between donor and recipient and by use of immunosuppressant drugs after transplant.
Serology is the scientific study of serum and other body fluids. In practice, the term usually refers to the diagnostic identification of antibodies in the serum. Such antibodies are typically formed in response to an infection, against other foreign proteins, or to one's own proteins.
Hemolytic disease of the newborn, also known as hemolytic disease of the fetus and newborn, HDN, HDFN, or erythroblastosis foetalis, is an alloimmune condition that develops in a fetus at or around birth, when the IgG molecules produced by the mother pass through the placenta. Among these antibodies are some which attack antigens on the red blood cells in the fetal circulation, breaking down and destroying the cells (hemolysis). The fetus can develop reticulocytosis and anemia. This fetal disease ranges from mild to very severe, and fetal death from heart failure can occur. When the disease is moderate or severe, many erythroblasts are present in the fetal blood, and so these forms of the disease can be called erythroblastosis fetalis.
A Coombs test, also known as antiglobulin test (AGT) is either of two blood tests used in immunohematology. They are the direct and indirect Coombs tests. The direct Coombs test detects antibodies that are stuck to the surface of the red blood cells. Since these antibodies sometimes destroy red blood cells, a person can be anemic and this test can help clarify the condition. The indirect Coombs detects antibodies that are floating freely in the blood. These antibodies could act against certain red blood cells and the test can be done to diagnose reactions to a blood transfusion.
The ABO blood group system is used to denote the presence of one, both, or neither of the A and B antigens on erythrocytes. In human blood transfusions it is the most important of the 36 different blood type classification systems currently recognized. A mismatch in this, or any other serotype, can cause a potentially fatal adverse reaction after a transfusion, or an unwanted immune response to an organ transplant. The associated anti-A and anti-B antibodies are usually IgM antibodies, produced in the first years of life by sensitization to environmental substances such as food, bacteria, and viruses.
The adaptive immune system, also referred as the acquired immune system, is a subsystem of the immune system that is composed of specialized, systemic cells and processes that eliminates pathogens by preventing their growth. The acquired immune system is one of the two main immunity strategies found in vertebrates.
Autoimmune hemolytic anemia (AIHA) occurs when antibodies directed against the person's own red blood cells (RBCs) cause them to burst (lyse), leading to an insufficient number of oxygen-carrying red blood cells in the circulation. The lifetime of the RBCs is reduced from the normal 100–120 days to just a few days in serious cases. The intracellular components of the RBCs are released into the circulating blood and into tissues, leading to some of the characteristic symptoms of this condition. The antibodies are usually directed against high-incidence antigens, therefore they also commonly act on allogenic RBCs. AIHA is a relatively rare condition, affecting one to three people per 100,000 per year. Autoimmune hemolysis might be a precursor of later onset systemic lupus erythematosus.
In ABO hemolytic disease of the newborn maternal IgG antibodies with specificity for the ABO blood group system pass through the placenta to the fetal circulation where they can cause hemolysis of fetal red blood cells which can lead to fetal anemia and HDN. In contrast to Rh disease, about half of the cases of ABO HDN occur in a firstborn baby and ABO HDN does not become more severe after further pregnancies.
hh, or the Bombay blood group, is a rare blood type. This blood phenotype was first discovered in Bombay, now known as Mumbai, in India, by Dr. Y. M. Bhende in 1952. It is mostly found in South Asia and parts of Middle East such as Iran.
The MNS antigen system is a human blood group system based upon two genes on chromosome 4. There are currently 46 antigens in the system, but the five most important are called M, N, S, s, and U.
The Lewis antigen system is a human blood group system. It is based upon two genes on chromosome 19: FUT3, or Lewis gene; and FUT2, or Secretor gene. Both genes are expressed in glandular epithelia. FUT2 has a dominant allele which codes for an enzyme and a recessive allele which does not produce a functional enzyme. Similarly, FUT3 has a functional dominant allele (Le) and a non-functional recessive allele (le).
In immunology, the immunoglobulin (Ig) isotype (class) is encoded by the constant region segments of the immunoglobulin gene which form the Fc portion and the lower segment of the Fab portion of an antibody. The expression of a specific isotype determines the function of an antibody via the specific binding to Fc receptor molecules on different immune effector cells. Isotype expression reflects the maturation stage of a B cell. Naive B cells express IgM and IgD isotypes with unmutated variable genes, which are produced from the same initial transcript following alternative splicing. Expression of other antibody isotypes occurs via a process of class-switch recombination (CSR) after antigen exposure. Class-switching is mediated by the enzyme AID and occurs after the B cell binds an antigen through its B cell receptor. Class-switching usually requires interaction with a T helper cell.
Isoantibodies are antibodies produced by an individual against isoantigens produced by members of the same species. In the case of the species Homo sapiens, for example, there are a significant number of antigens which are different in every individual. When antigens from another individual are introduced into another's body, these isoantibodies immediately bind to and destroy them.
Immune tolerance in pregnancy or maternal immune tolerance is the immune tolerance shown towards the fetus and placenta during pregnancy. This tolerance counters the immune response that would normally result in the rejection of something foreign in the body, as can happen in cases of spontaneous abortion. It is studied within the field of reproductive immunology.
Donath–Landsteiner hemolytic anemia (DLHA) is a result of cold-reacting antibody immunoglobulin (Ig) induced hemolytic response inside vessels leading to anemia and, thus, a cold antibody autoimmune hemolytic anemias (CAAHA).
Blood typing is a medical laboratory test used to identify the antigens on a person's red blood cells, which determine their blood type. Routine blood typing involves determining the ABO and RhD type, and is performed before blood transfusions to ensure that the donor blood is compatible. It is also used to help diagnose hemolytic disease of the newborn, a condition caused by incompatibility between the blood types of a mother and her baby. ABO typing involves both identification of ABO antigens on red blood cells and identification of ABO antibodies in the plasma. Other blood group antigens, such as RhC/c and E/e or Kell, may be tested for in special situations.
References
- 1 2 Magnetic immunodiagnostic method for the demonstration of antibody/antigen complexes especially of blood groups Archived 2012-02-29 at the Wayback Machine Yves Barbreau, Olivier Boulet, Arnaud Boulet, Alexis Delanoe, Laurence Fauconnier, Fabien Herbert, Jean-Marc Pelosin, Laurent Soufflet. October 2009
- ↑ Letter to the Editor: “Natural” Versus Regular Antibodies Archived 2011-07-14 at the Wayback Machine Journal The Protein Journal Publisher Springer Netherlands ISSN 1572-3887 (Print) 1573-4943 (Online) Issue Volume 23, Number 6 / August, 2004 Category Letter to the Editor DOI 10.1023/B:JOPC.0000039625.56296.6e Page 357 Subject Group Chemistry and Materials Science Online Date Friday, January 07, 2005
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