Researchers want to examine additional Indian blood donations to determine whether the marker exists in only one tribe, officials said.
“We believe it's possible that the more Choctaw you are, the more chance that there will be this antibody,” OBI reference lab manager Rosemary Persa said. “At this point, it's basically a needle in a haystack trying to find donors with this kind of antibody.”
The marker was discovered by accident in 1997 after researchers in an OBI lab noticed the presence of the ENAV (MNS42) antibody in one donor's blood. Since then, the antibody has been found in only two other donors' blood, and all three donors are of Choctaw descent, officials said.
The find is significant because it will help OBI locate suitable blood for patients with the rare antibodies.
Dr. James Smith, OBI's medical director, said the discovery was noticed when blood samples showed a peculiar marker on their red blood cell walls.
“Everyone has a different phenotype (characteristic) on their red cells, but this one was really rare,” he said.
Race and specific antigen markers are not uncommon, Smith said. He cited sickle-shaped cells among black people. Those antigens evolved to help protect the carriers from malaria.
He said it is likely that the Indian-based antigen developed several generations ago and was passed down genetically. OBI samples with the rare antigen were found within the last three to four years.
The three donors who had the antibodies were of Choctaw descent, and all three lived in southeastern Oklahoma, officials said. Researchers then realized that the blood samples with the rare markers came from hospitals.
Hospital blood samples differ from donors' blood in that they are random, whereas people who donate blood are traceable from their intake information, Smith said.
Because the random samples came from people of Choctaw descent, more carriers of the rare antigen are possible, he said.
“It may be in other tribes that we don't know about,” Smith said.
Choctaw Nation spokeswoman Judy Allen said the tribe was unaware that its members might have a rare marker in their blood makeup.
“The way we understand it is that having this marker in our blood helps others with this kind of blood heal faster from having an exact match,” Allen said. “So, of course, we encourage our people to donate blood.”
The Choctaw Nation has just fewer than 200,000 registered citizens.
Officials said few studies have been conducted on blood groups in American Indians. The occurrence of the rare antibody is less than one-tenth of 1 percent.