All mammalian cells express ABO antigens, I believe. What I object to about D'Adamo's work is that he has started with a reasonable hypothesis, and has failed to develop it further. The blood agglutinating effects of lectins were discovered over 100 years ago. Lectins do far more than this, yet that is all that D'Adamo is interested in. They are the most versatile biological poisons I am aware of. They can cause all kinds of mischief, without necessarily causing any blood clotting or attaching to cells. Thus D'Adamo is a disappointment as he has stagnated, he has failed to progress, to develop. He seems to have ignored everything else that has been discovered about lectins causing havoc, as he doesn't want to change his precious theory or affect his sales. D'Adamo's book has too soul butter and hogwash for my liking. I gave up half way through reading it. As for there being good and bad lectins- absolutely! I think of lectins much like bacteria- there are good and bad ones.. So how do we separate them out- I've been trying to get a sensible response from lectin scientists but they're all a bit test tube oriented. It comes down to how we react hem or them to us. I categorise them as reactive (having effects on our physiology) or non-reactive (having no measurable effect on our physiology). Most of the reactive ones are defensive lectins (their role is to defend the plant from predators). Most of the non-reactive ones have physiological roles in the plant or animal (which haven't really been figured out yet). It seems like we may have adapted to some defensive lectins in the edible nuts (maybe some of us haven't)(BTW although everyone calls almonds paleo, natural almonds are not as they contain cyanide/cyanogens- we eat a mutant that came out about 100 years ago with low cyanide. So, I think almonds aren't really paleo. I suspect they may have the odd other toxin or two). By the way, grain eating birds have adapted to the lectins in grains. I call the reactive ones Hannibal lectins after Hannibal Lecter as they are so devious, insidious and nasty. They are exquisitely versatile as they can trigger almost any receptor in the body and make cells do things they would never have dreamed of, or simply die. Ben Balzer