Blood type b in asian countries Essays

Blood type b in asian countries Essays Blood type b in asian countries Paper Blood type b in asian countries Paper 2001). These variants harbored missense mutations in specific exons that generate alterations in the carbohydrate chain of the ABO antigens. Such reports have significantly affected serological protocols that were closely associated with donor-patient compatibility testings, because these variants had the capacity to express the antigens at a broader range of degree of expression than what was classically described. This dilemma may cause mistyping of blood groups which, in turn, may affect transfusion and transplantation procedures. The ABO blood group system has been determined to follow a unique geographic distribution (Fukumori et al. , 1996). Frequencies of individuals with blood type B are known to be particularly high in Asian countries, ranging up to 30% is specific populations such as the Himalayans. The Himalayan region has been reported to have a history of smallpox and bubonic plague epidemics, which are specific medical illnesses that confer particular physiological responses in the body that blood types A and O are selected against (Yamamoto et al. , 1993). Such selection is also associated with the development of resistance to the other antigens, hence blood type B is said to be fixed in the area through the mechanism of genetic drift. Investigations on the ABO locus has revealed that random sequence variations occur within this region, resulting in substitutions of nucleotides bases that are presumably less susceptible to selection pressure, hence it is possible to trace the phylogeny of the B alleles in a more robust way. The diversification of the B locus may be a result of two genetic mechanisms. Point mutations may have occurred in the consensus ABO locus due to recombination events (Olsson and Chester, 1995). The fixation rates of a mutation may be calculated based on its extent of homology to the consensus B locus. This may be observed in the high frequencies in Asian populations and the low frequencies in different white populations. Recombination facilitates the generation of new variants of blood type B may also be enhanced by inter-lineage sequence transfer, resulting in intermediate products of the B allele. Blood type B is strongly associated with specific medical diseases such as esophageal carcinoma, infantile diarrhea and typhoid fever (Su et al. , 2001). These associations may be due to the selection against the other blood types during the onset of the medical illness. In addition, the B antigen is maximally expressed in these populations because the physiological settings of these individuals are optimal for the fixation of the blood type B and its related subtypes, as well as the increased suppression of expression of the A antigen in the red blood cells. The ABO blood typing system should therefore be cautiously analyzed especially when dealing with serology, transfusion and transplantation procedures, together with the ethnicity data that is gather from the patient, in order to avoid mistyping and adverse rejection reactions. References Fukumori Y, Ohnoki S, Shibata H, Nishimukai H (1996): Suballeles of the ABO blood group system in a Japanese population. Hum. Hered. 46:85-91. Olsson ML, Chester MA (1995): A rapid and simple ABO genotype screening method using a novel B/O2 versus A/O1 discriminating nucleotide substitution at the ABO locus. Vox Sang. 69:242-247. Olsson ML, Irshaid NM, Hosseini-Maaf B, Hellberg A, Moulds MK, Hannele Sareneva, Chester MA (2001): Genomic analysis of clinical samples with serologicABO blood grouping discrepancies: identification of 15 novel A and B subgroup alleles. Blood 98:1585-1593. Su M, Lu SM, Tian DP, Zhao H, Li XY, Li DR, Zheng ZC (2001): Relationship between ABO blood groups and carcinoma of esophagus and cardia in Chaoshan inhabitants of China. World J. Gastroenterol. 7(5):657-61. Yamamoto F, McNeill PD, Yamamoto M, Hakomori S, Bromilow IM, Duguid JK (1993): Molecular genetic analysis of the ABO blood group system, 4:another type of O allele. Vox Sang. 64:175-178.