Rh factor : 'Rh ' factor is a antigen present on cell meribrane of RBC and there is no anti-Rh antibodies (are present) in humans. 'Rh' factor was first discovered by Landsteiner and Weiner in the plasma membrane of RBCs of rhesus monkeys. In India 97% individuals possess Rh antigen, so called as Rh-positive. AB and O blood groups was discovered by Landsteiner and AB by Decastello and Sturle.