FUT2 (Fucosyltransferase 2) is a gene that encodes an enzyme involved in the synthesis of histo-blood group antigens and the determination of secretor status. It catalyzes the transfer of fucose to specific molecules, enabling the production of glycoproteins and glycolipids found in bodily fluids and epithelial tissues. FUT2 activity influences the expression of the H antigen — a key precursor to ABO blood group antigens — and plays a critical role in whether these antigens are present in secretions like saliva.