Every group has a story; AB− is the one with the smallest supporting cast. Found in roughly 1 in 250 Indians, it is the rarest of the eight common groups, and the most misunderstood, because its red cells reach almost nobody while its plasma reaches everybody. ## What AB− means Red cells carry both A and B antigens but lack the Rh (D) antigen. Plasma carries neither anti-A nor anti-B antibodies. ## Red cells: the narrow road AB− red cells can be given to just two groups: AB− and AB+ patients. And an AB− patient has it harder still, they can receive red cells only from AB−, A−, B− or O− donors. Every one of those is an uncommon group. In an emergency, a bank may be juggling four searches at once to find one compatible unit. ## Plasma: the wide road The same blood, spun into plasma, flips the story. No anti-A or anti-B antibodies means AB plasma (whether AB+ or AB−) suits patients of any group. For burn wards, liver patients and clotting crises, an AB− donor’s plasma is exactly as universal as anyone’s. Apheresis donation, where plasma is collected and red cells returned, lets AB− donors do this repeatedly. ## Why rarity cuts both ways “Rare” is often said like a badge; for blood banks it is a logistical sentence: - Few donors, a small pool must cover every AB− patient in the region.
- Few recipients, demand is also sparse and unpredictable, so no bank can justify a big standing shelf of AB− red cells.
- Slow-moving stock, units age on the shelf between rare requests, and red cells expire in about 35,42 days. The system’s answer is not stockpiling, it is registries: knowing exactly who the AB− donors are, keeping their details fresh, and calling them the day a rare patient appears. That is precisely what a donor register does, and why reconfirmation (“still willing, still here?”) matters most for the rarest groups. ## If you are AB− You are one in a few hundred, and on the plasma side, one in everyone. Register, stay reconfirmable, and ask your centre about apheresis. The next AB− patient in Assam will be glad you exist. Register as a donor → ## Explore AB+, the universal recipient → · rare blood types and the Bombay group → · the genetics of blood groups → · all eight groups → ## Quick answers about AB− Who can AB− donate to? Red cells: AB− and AB+ patients only. Plasma: every patient, every group, AB plasma carries no anti-A and no anti-B. Who can donate to AB− patients? O−, A−, B− and AB−, all the Rh-negative groups. What percentage of Indians have AB−? About under 1% of Indians, the rarest of the eight. Is AB− rare in India? Yes, the rarest blood group in India. An AB− patient in an emergency can only receive from roughly 1 in 150 people. What antigens and antibodies does AB− have? A and B antigens, no Rh(D). Plasma carries no anti-A or anti-B antibodies, the reason AB− plasma is universal.