Packed red blood cells Rh type, specifically the phenotype, and the "screen" refers to testing for atypical antibodies that might cause transfusion problems. The typing and screening are also performed on donor blood. The blood groups represent antigens on the surface of the red blood cells which might react with antibodies in the recipient. The ABO blood group system has four basic phenotypes: O, A, B, and AB. In the former Soviet Union these were called I, II, III, and IV, respectively. There are two important antigens in the system: A and B. Red cells without A or B are called type O, and
Hh blood group did not inherit the mother's Bombay phenotype. In practice, cases of HDN caused in this way have not been described. This may be possible due to the rarity of the Bombay phenotype but also because of the IgM produced by the immune system of the mother. Since IgMs are not transported across the microscopic placental blood vessels (like IgG are) they cannot reach the blood stream of the fetus to provoke the expected acute hemolytic reaction. Hh blood group The h/h blood group, also known as Oh or the Bombay blood group, is a rare blood type. This blood phenotype