Indian blood group system

The Indian blood group system (In) is a classification of blood based on the presence or absence of inherited antigens that reside within the CD44 molecule that is expressed on the surface of blood cells.^[1] It is named so because 4% of the population in India possess it.^[2] Most individuals express the In^b antigen that results from an arginine residue at position 46 of CD44 . The In^a blood type results from a substitution proline for arginine at this same position.