Your blood type is determined by the antigens present on the surface of your red blood cells. If you have one antigen, then you have the antibodies for the other. The antigens are A and B. You can have just one (A or B), both (AB), or none (O). If you have A blood, then you have anti-B antibodies circulating in your blood, and vice versa. These antibodies will latch onto those antigens and make blood clots, which is why you have to have the right blood type. If you have AB blood then you have no antibodies which is why A is the "universal reciever". If you have O then you have no antigens so you have both anti-A and anti-B antibodies. But since O has no antigens, no antibodies will attack it, thats why O is the "universal donor."
Hope I didn't confuse you too much. Email me if you need some more help [email protected]
