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How are transplantation antigens inherited from parents?
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transplant
British surgeon Andrew Ready flushing a donated kidney during a transplant at Queen Elizabeth Hospital, Birmingham, England, 2006.
Transplantation antigens, known as the major histocompatibility complex (MHC) or human leukocyte antigens (HLA), are governed by genes located on chromosome 6.12
In accordance with Mendelian laws of inheritance, an individual inherits one copy of chromosome 6 from each parent. Because these genes are expressed in a codominant fashion, the specific set of antigens an individual possesses is determined by the combination of alleles received from both the mother and the father.23
This inheritance pattern has significant implications for transplant surgery:
- Parent-to-child: A child will always be at least half-matched with a parent because they inherit one chromosome 6 from that parent.2
- Siblings: Because siblings inherit their chromosomes from the same parents, there is a one-in-four (25 percent) chance that they will inherit the same paternal and maternal chromosomes, resulting in a complete HLA match. There is also a one-in-two chance of a half-match and a one-in-four chance of no match.23
Due to the high number of alleles at each HLA locus, it is extremely rare for two unrelated individuals to have identical HLA genotypes.43