Researchers have discovered a new type of human blood type, type A(B), that only three people in the world have this type. The discovery was made when the blood of patients and donors in a Thai hospital was being studied. The type AB is caused by four gene mutations and could lead to more rare blood types still undiscovered. The antigens of donor and patient blood are crucial for transfusions, as they can alert the immune system to foreign bodies. However, even rarer blood types than O negative exist, with 50 people on the planet having Rh-negative blood, and only one individual known to have Gwada negative blood. Researchers found four mutations on the B(A) type that differed from those associated with other blood types.