Scientists have discovered the two proteins in red blood cells that cause the rare Langereis and Junior blood types, Science Daily reported Thursday.
"Only 30 proteins have previously been identified as responsible for a basic blood type," University of Vermont biologist Bryan Ballif says, "but the count now reaches 32."
Ballif and his colleagues identified the two molecules as specialized transport proteins ABCB6 and ABCG2, identifying the molecular basis for the two newest blood types.
He says this knowledge can be "a matter of life and death" when it comes to organ transplant or blood transfusion.
Sometimes the body rejects a newly transplanted tissue or blood, even though the blood types might match, leading to complications or even death.
The rejection is often caused by the way the immune system distinguishes self from not-self.
"If our own blood cells don't have these proteins, they're not familiar to our immune system," Ballif explains. This causes the body to define the new blood/tissue as "not-self," then the body develops antibodies against it, killing the "invaders."
He says these unexplained rejections in the rare blood types may have to do with newly discovered proteins. While the blood types were identified decades ago, the genetic basis had been unidentified until now, meaning some people never knew if they had a positive or negative blood type. This often led to blood transfusion problems or mother-fetus incompatibility.
However, with these findings, it will be much easier for doctors to recognize patients with these rare blood types.
According to Ballif, they are found in only certain ethnicities, with more than 50,000 Japanese believed to be Junior negative.
In addition, both of the new-found proteins were associated with anticancer drug resistance, which could have implications for improved cancer treatment.
Langereis and Junior have yet to be recognized by the International Blood Transfusion Society, which recognizes twenty-eight additional blood types other than ABO and Rhesus (Rh), such as Duffy, Kidd, Diego and Lutheran.
Ballif's team is searching for more unknown blood types, where they cannot identify the protein causing complications.
These other blood types are extremely rare, but he says it's important to identify them because "if you're that one individual, and you need a transfusion there's nothing more important for you to know."