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The MNS antigen system is a human blood group system based upon two genes (glycophorin A and glycophorin B) on chromosome 4. There are currently 46 antigens in the system,〔Daniels G, Flegel WA, Fletcher A, et al. International Society of Blood Transfusion Committee on Terminology for Red Cell Surface Antigens: Cape Town Report. Vox Sang 2007; 92: 250-3.〕〔Poole J, Daniels G. Blood Group Antibodies and Their Significance in Transfusion Medicine. Transfus Med Rev 2007; 21: 58-71.〕〔Daniels G. Human Blood Groups. 2nd Ed. Oxford: Blackwell Science, 2002.〕 but the five most important are called M, N, S, s, and U. The system can be thought of as two separate groups: the M and N antigens are at one location on the ECM and S, s, and U are on a closely related location. The two groups are very closely located together on chromosome 4 and are inherited as a haplotype. ==The MN blood group== The MN blood group in humans is under the control of a pair of co-dominant alleles, LM and LN. Most people in the Eskimo population are M/M, while this genotype is rare among Aborigines. In fact, they tend to possess the opposite genotype (N/N). The MN blood group system is under the control of an autosomal locus found on chromosome 4, with two alleles designated LM and LN. The blood type is due to a glycoprotein present on the surface of red blood cells, which behaves as a native antigen. Phenotypic expression at this locus is codominant because an individual may exhibit either one or both antigenic substances. Frequencies of the two alleles vary widely among human populations.〔Ralph H. Kathan and Anthony Adamany. 1967. Comparison of Human MM, NN, and MN Blood Group Antigens. The Journal of Biological Chemistry, 242, 1716-1722.〕 M+ and N+ RBCs are common (75% of population) and M+N+ cells are the most common genotype (50% of population). These antigens were an early discovery and are some of the oldest blood antigens known after the ABO system. They were first described by Karl Landsteiner and Philip Levine in 1927. Anti-M and anti-N antibodies are usually IgM and are rarely associated with transfusion reactions. Anti-N is sometimes seen in dialysis patients due to cross-reactions with the residual formaldehyde from sterilizing the equipment. This is usually irrelevant for transfusion since this variant of the antibody does not react at body temperature. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「MNS antigen system」の詳細全文を読む スポンサード リンク
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