Lewis antigen system
Encyclopedia
The Lewis antigen system is a human blood group system
based upon genes on chromosome 19 q13.3, (FUT2) and 19p13.3 (FUT3), which both have fucosyltransferase activity. There are two main types of Lewis antigens, Lewis a and Lewis b. They are red cell antigens which are not produced by the erythrocyte itself. Instead, Lewis antigens are a component of exocrine epithelial
secretions, and are subsequently adsorbed onto the surface of the erythrocyte. However, absorption can only take place if the Se (secreter) gene is also present.
It is possible to have any combination of Lewis a, Lewis b, both or neither antigens. The most common are Lewis a negative and Lewis b positive Le(a-b+). Having both antigens present on red cells is extremely rare and is thought to be caused by a weak expression of the secretor gene.
The link between the Lewis blood group and secretion of the ABO blood group antigen
s was possibly the first example of multiple effects of a human gene
. The presence of fucosyltransferase
converts the Lewis a antigen to Lewis b. This is the same fucosyltransferase which can convert membrane bound A, B or H antigens into soluble A, B and H, allowing the person to secrete them into body fluids. Therefore, people with Lewis a antigens will not secrete the A, B or H antigens (and are called ABH non-secretors), and the presence of the Lewis b antigen is only found in secreters. Lewis negative (Le a-, Le b-) can be either secretors or non-secretors.
Human blood group systems
The International Society of Blood Transfusion currently recognises 30 major blood group systems . Thus, in addition to the ABO antigens and Rhesus antigens, many other antigens are expressed on the red blood cell surface membrane...
based upon genes on chromosome 19 q13.3, (FUT2) and 19p13.3 (FUT3), which both have fucosyltransferase activity. There are two main types of Lewis antigens, Lewis a and Lewis b. They are red cell antigens which are not produced by the erythrocyte itself. Instead, Lewis antigens are a component of exocrine epithelial
Epithelium
Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of structures throughout the body, and also form many glands. Functions of epithelial cells include secretion, selective...
secretions, and are subsequently adsorbed onto the surface of the erythrocyte. However, absorption can only take place if the Se (secreter) gene is also present.
It is possible to have any combination of Lewis a, Lewis b, both or neither antigens. The most common are Lewis a negative and Lewis b positive Le(a-b+). Having both antigens present on red cells is extremely rare and is thought to be caused by a weak expression of the secretor gene.
The link between the Lewis blood group and secretion of the ABO blood group antigen
Antigen
An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...
s was possibly the first example of multiple effects of a human gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
. The presence of fucosyltransferase
Fucosyltransferase
A fucosyltransferase is an enzyme that transfers an L-fucose sugar from a GDP-fucose donor substrate to an acceptor substrate...
converts the Lewis a antigen to Lewis b. This is the same fucosyltransferase which can convert membrane bound A, B or H antigens into soluble A, B and H, allowing the person to secrete them into body fluids. Therefore, people with Lewis a antigens will not secrete the A, B or H antigens (and are called ABH non-secretors), and the presence of the Lewis b antigen is only found in secreters. Lewis negative (Le a-, Le b-) can be either secretors or non-secretors.
External links
- Lewis at BGMUTBGMUTThe BGMUT Database documents allelic variations in the genes encoding for human blood group systems. It was set up in 1999 through an initiative of the Human Genome Variation Society . Since 2006, it has been a part of the dbRBC resource of NCBI at the NIH...
Blood Group Antigen Gene Mutation Database at NCBINational Center for Biotechnology InformationThe National Center for Biotechnology Information is part of the United States National Library of Medicine , a branch of the National Institutes of Health. The NCBI is located in Bethesda, Maryland and was founded in 1988 through legislation sponsored by Senator Claude Pepper...
, NIH - http://www.right4eu.us/Lewisgroup.html