Xg antigen system

Xg blood group
Interpretation of antibody panel to detect patient antibodies towards the most relevant human blood group systems, including Xg. Further information: Blood compatibility testing
Identifiers
Symbol	XG
Alt. symbols	PBDX
NCBI gene	7499
HGNC	12806
RefSeq	NM_175569
Other data
Locus	Chr. X p22.32

The XG antigen is a red blood cell surface antigen discovered in 1962 ^[1] by researchers at the MRC Blood Group Unit. ^[2]

The PBDX gene that encodes the antigen is located on the short arm of the X chromosome. ^{[3] [4]} Since males normally have one X chromosome they are considered hemizygotes. Since women have two copies of the gene and could be heterozygotic for the presence or absence of the functioning gene they could (through the process of lyonisation) express the functioning protein on just some of their red blood cells.^{[ citation needed ]}

Clinical diagnostic

Clinical testing in patient care for Xg antigens follows published minimum quality and operational requirements, ^[5] similar to red cell genotyping for any of the other recognized blood group systems. Molecular analysis can identify gene variants (alleles) that may affect Xg antigens expression on the red cell membrane.

Frequency

Population frequencies of Xa [6]
Population	Sample N	Xg %
Australian Aborigines	352	79
Chinese, mainland	171	60
North Europeans	5,388	66
Indians, Bombay	100	65
Israelis	201	66
American Indians	308	77
New-Guineans	263	85
New York's Afro-Americans	219	55
Sardinians	322	76
Taiwan Chinese	178	53
Taiwan Aborigines	164	38

References

1. Tippett P, Ellis NA (October 1998). "The Xg blood group system: a review". Transfus Med Rev. 12 (4): 233–57. doi:10.1016/S0887-7963(98)80001-1. PMID   9798268.
2. Mann, J. D., Cahan, A., Gelb, A. G., Fisher, N., Hamper, J., Tippett, P., Sanger, R., Race, R. R A sex-linked blood group. Lancet. 1962;279:8.
3. Ellis NA, Tippett P, Petty A, et al. (November 1994). "PBDX is the XG blood group gene". Nat. Genet. 8 (3): 285–90. doi:10.1038/ng1194-285. PMID   7533029. S2CID   36695727.
4. LINDSTEN J, FRACCARO M, POLANI PE, HAMERTON JL, SANGER R, RACE RR (February 1963). "Evidence that the Xg blood group genes are on the short arm of the X chromosome". Nature. 197 (4868): 648–9. Bibcode:1963Natur.197..648L. doi:10.1038/197648a0. PMID   13930842. S2CID   4209911.
5. "Association for the Advancement of Blood & Biotherapies (AABB). (2025). Standards for molecular testing for red cell, platelet, and neutrophil antigens, 7th ed. (ISBN: 978-1-56395-516-7)".
6. Harrison et al. (1977): Human biology – An introduction to human evolution, variation, growth and ecology. Oxford University Press, Oxford, ISBN   978-0-19-857165-0.