Define Universal Donor and Recipients

Based on the above mentioned concept, O group individuals are sometimes considered as 'universal donors ', since they have no antigens and the blood does not generate any antibody reaction. Group AB is called 'universal recipients ' as their plasma has no antibody. They can receive blood from anybody as highlighted in Table herewith. The donor cells irrespective of whatever antigen they contain will not cause a reaction.

Table: The blood groups and the universal recipient and donor concept

Other than the A and B antigen, some other factor is also present on the surface of the RBCs. What is this factor and the corresponding blood grouping system?