Everything about Hh Antigen System totally explained
hh is a rare
blood group. This is also called Bombay blood group. Individuals with the rare
Bombay phenotype (
hh) don't express
H antigen (also called "substance H") (the antigen which is present in blood group O). As a result, they can't make
A antigen (also called "substance A") or
B antigen (also called "substance B") on their
red blood cells, whatever
alleles they may have of the A and B blood-group genes, because A antigen and B antigen are made from H antigen; receiving blood which contains an antigen which has never been in the patient's own blood causes an
immune reaction. As a result, people who have Bombay phenotype can donate to any member of the
ABO blood group system (unless some other
blood factor gene, such as
Rhesus, is incompatible), but they can't receive any member of the
ABO blood group system's blood (which always contains one or more of A and B and H antigens), but only from other people who have Bombay phenotype. The usual tests for ABO blood group system would show them as group O, unless the hospital worker involved has the means and the thought to test for Bombay group.
Transfusion compatibility
Individuals with Bombay phenotype
blood group can only be transfused with
blood from other Bombay phenotype individuals. Given that this condition is very rare, any person with this blood group who needs an urgent
blood transfusion will probably be unable to get it, as no blood bank would have any in stock. Those anticipating the need for blood transfusion (for example in scheduled
surgery) may bank blood for their own use (for example an
autologous blood donation), but this option isn't available in cases of accidental injury.
Genetics
Patients who test as type O may have the
Bombay phenotype if they've inherited two
recessive alleles of the
H gene, (their blood group is O
h and their genotype is "hh"), and so don't produce the "H" carbohydrate (
fucose) that's the precursor to the "A" and "B" antigens. It then no longer matters whether the A or B enzymes are present or not, as no A or B antigen can be produced since the precursor antigen H isn't present.
Despite the designation
O, O
h negative isn't a sub-group of any other group. When Bombay blood group was first encountered, it was found not to contain antigens A or B and so was thought to be of group O. But experience showed that Bombay group patients couldn't even safely receive normal O-group blood, and this proved to be because they lacked the H antigen.
Because both parents must carry this recessive allele to transmit this blood type to their children, the condition mainly occurs in small closed-off communities where there's a good chance of both parents of a child either being of Bombay type, or being
heterozygous for the "h" gene
allele and so carrying the Bombay characteristic as
recessive. Other examples may include
noble families, which are inbred due to custom rather than local genetic variety.
This blood phenotype was first discovered in Bombay, now known as
Mumbai, in
India, by Dr. Y.M. Bhende.
References in popular culture
- Television: Yakitate Japan Episode 49 of Monoco Cup Arc — Reunion at the VIP Seat! Heaven Again! — the clown Pierrot has Bombay blood. He gets wounded in the course of the show, and being rare enough that according to the show only several hundred people in the world would have it. It turns out his father is the king of Monaco, who also has Bombay blood.
- Television: Psi Factor The OSIR team encountered a young woman with the Bombay phenotype while working to solve the case of a haunting in the underground maintenance tunnels of a major city. The ghost would later be revealed as the spirit of her dead infant.
- Television: Get Backers Episode 35 — Get Back the Life! — a little girl who has Bombay blood gets in a car accident and badly needs blood transfusions; the blood transfusions meant for her from a neighboring hospital were stolen by a shady organization for research purposes.
- On General Hospital, Monica believed that her son, AJ Quartermaine, couldn't be her husband Alan's child and must have been the product of her affair with Rick, because AJ's blood type couldn't have arisen from hers and Alan's. It then turned out that Alan had the Bombay phenotype, and AJ really was his son.
- The Harvard Medical School class of 2009 Second Year Show featured a Bollywood-style dance performance, with dancers representing blood cells inside the body of a character with Bombay-phenotype blood.
- Anime: Kindaichi Case Files SP - Legendary Vampire Murders Kindaichi_Case_Files.
- Movies: The Telugu (a south Indian language) movie Okkadunnadu's main theme is based on the Bombay blood group.
Further Information
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