Thanks to James' donations, Anti-D, a medication, can be made using the antibodies and given to pregnant women to help keep their unborn babies healthy.
James Harrison has extraordinary blood.
At 14, Harrison made a pledge that he would donate blood when he turned 18 after a major chest surgery that required 13-liters (0.26 gal) of blood. "In Australia, up until about 1967, there were thousands of babies dying each year, doctors didn't know why", Jemma Falkenmire, of the Australian Red Cross Blood Service, told CNN in 2015.
The condition develops when the infant's mother has rhesus negative blood, and the baby inherits rhesus positive blood from the father. In the worst cases, it can result in brain damage, or death, for the babies.
At the moment, only 200 donors are qualified for the Anti-D program, though Australian Red Cross Blood Service officials are hoping more people will be eligible for their program going forward.
When Mr Harrison started donating, his blood was deemed so special that his life was insured for one million Australian dollars.
The drug works as an injection that prevents a pregnant woman's body from developing possibly harmful antibodies that could negatively affect her next baby.
As recalled by the Washington Post, Harrison chose to become a blood donor when he was 14-years-old, after he survived a chest operation that required the removal of one of his lungs, keeping him in the hospital for three months. He was even able to donate to help his own daughter, Tracey, to safely have her little boy. As her body starts feeling the baby's blood cells as a "foreign threat", she may then start producing antigens that can be prove to be risky for the baby. So that makes me feel good.
The discovery of Harrison's antibodies was an absolute game changer, Australian officials said.
Ms Falkenmire said that up until 1967, 'there were literally thousands of babies dying each year, doctors didn't know why and it was bad.
That would be more than two million lives, according to the blood service, and for that Harrison is considered a national hero in Australia.
After 1173 donations, the 81-year-old has finally hung up his blood bag. He's won numerous awards for his generosity, including the Medal of the Order of Australia, one of the country's most prestigious honors. On Friday, Harrison made his final donation, as he reached the maximum allowable age for donors in Australia.