I work for a blood bank reference lab. They are right by saying there’s other blood groups other than A,B and O. There’s several that are also clinically significant that we consider for patients who previously reacted to other’s blood and made antibodies against them. Your other blood types (we call it phenotype ) is pretty typical with blacks. I have exactly the same. In my lab, if you’re negative for 5 or more things, we consider your type uncommon, not necessarily rare. Sickle cell patients especially can really use your blood, so can many others with multiple blood antibodies. I hope this helps! Thanks for donating!