For something so intrinsically a part of us, it seems there’s plenty we’re in the dark about when it comes to our blood type. Indeed, according to various surveys, anywhere from 35 to 50 percent of people in the Western world just plain don’t know what their type even is.

That’s why we here at Medical Daily have decided to pull back the curtain and lay down some interesting factoids about blood types and their continuing, if sometimes overexaggerated, importance to our lasting health.

When you’re trying to remember your blood type, you’re likely grasping for two things: is it A, B, AB, or O? And is it positive or negative?

But your precise blood type is vastly more complex than that. Our red blood cells are constantly covered by different kinds of antigens — as many as 600 known currently, though only around a quarter of these are commonly seen. These antigens, inherited from our parents, can be broken down into 35 broad blood groups, with the most relevant being the ABO group and the Rhesus group. And of the 61 antigens in the Rhesus group, the most essential is the D antigen.

When it comes time for a blood transplant, our body can usually only accept donated blood cells compatible with the antigens from these two groups. That’s because people with the A, B and O types produce antibodies that target the A or B antigens not native to their body. In other words, people with an A blood type produce antibodies for B and vice versa. People with the O type lack both A and B antigens and therefore produce antibodies for both, while people with the AB type don’t produce antibodies for either.

Similarly, people without the D antigen typically can’t use blood positive for it, while people who have a positive D type can use D- or D+ blood.

Thus, O- people are considered universal donors, while AB+ people can receive blood from anyone else. Interestingly enough, the opposite is true when we only need to transplant the liquid component of blood, called plasma, into someone else’s body.

Written by jale