"AB-" is a blood type classification in the ABO blood group system. It is characterized by the presence of both A and B antigens on the surface of red blood cells, while lacking anti-A and anti-B antibodies in the plasma. This means that individuals with the AB- blood type can receive blood from all other blood types, making them universal recipients. The "negative" in AB- indicates the absence of the Rh factor, a specific protein that can be present on red blood cells. People with AB- blood type can donate to other AB blood types, but they can only receive blood from AB-, A-, B-, and O- blood types. Understanding blood types is crucial for safe blood transfusions and organ transplants.