Blood group antigens
Blood is classified into different groups according to the presence or absence of molecules called antigens on the surface of every red blood cell in a person's body. Antigens determine blood type and can either be proteins or complexes of sugar molecules (polysaccharides). The genes in the blood group antigen family provide instructions for making antigen proteins. Blood group antigen proteins serve a variety of functions within the cell membrane of red blood cells. These protein functions include transporting other proteins and molecules into and out of the cell, maintaining cell structure, attaching to other cells and molecules, and participating in chemical reactions.
Blood group antigens play a role in recognizing foreign cells in the bloodstream. For example, if a person with blood type A receives a blood transfusion with blood type B, the recipient's immune system will recognize the type B cells as foreign and mount an immune response. Antibodies against type B blood cells (anti-B antibodies) are made, which attack and destroy the type B blood cells. This sort of blood type mismatch can lead to illness. Some blood types are associated with more severe immune reactions than others. The blood type of donated cells, or tissues in the case of organ donation, is checked before being given to a recipient to prevent this immune response.
There are 29 recognized blood groups, most involving only one gene. Variations (polymorphisms) within the genes that determine blood group give rise to the different antigens for a particular blood group protein. For example, changes in a few DNA building blocks (nucleotides) in the ABO gene give rise to the A, B, and O blood types of the ABO blood group. The changes that occur in the genes that determine blood group typically affect only blood type and are not associated with adverse health conditions, although exceptions do occur.
Example of a gene in this gene family: SLC4A1
The HUGO Gene Nomenclature Committee (HGNC) provides an index of gene families and their member genes.
Byrne KM, Byrne PC. Review: other blood group systems--Diego,Yt, Xg, Scianna, Dombrock, Colton, Landsteiner-Wiener, and Indian. Immunohematology. 2004;20(1):50-8. Review. PubMed: 15373669.
Daniels G. The molecular genetics of blood group polymorphism. Transpl Immunol. 2005 Aug;14(3-4):143-53. Epub 2005 Apr 26. Review. PubMed: 15982556.
Daniels G. Functions of red cell surface proteins. Vox Sang. 2007 Nov;93(4):331-40. Review. PubMed: 18070278.
Eyler CE, Telen MJ. The Lutheran glycoprotein: a multifunctional adhesion receptor. Transfusion. 2006 Apr;46(4):668-77. Review. PubMed: 16584446.
Palacajornsuk P. Review: molecular basis of MNS blood group variants. Immunohematology. 2006;22(4):171-82. Review. Erratum in: Immunohematol. 2007;23(1):44. PubMed: 17430076.
Quill E. Medicine. Blood-matching goes genetic. Science. 2008 Mar 14;319(5869):1478-9. doi: 10.1126/science.319.5869.1478. PubMed: 18339916.
Westhoff CM, Reid ME. Review: the Kell, Duffy, and Kidd blood group systems. Immunohematology. 2004;20(1):37-49. Review. PubMed: 15373667.
Yamamoto F. Review: ABO blood group system--ABH oligosaccharide antigens, anti-A and anti-B, A and B glycosyltransferases, and ABO genes. Immunohematology. 2004;20(1):3-22. Review. PubMed: 15373665.