Natural anti-carbohydrate antibodies (NAbC) are antibodies that target glycans and are continuously produced without apparent external antigen stimulation. Clinically, NAbC are recognized by the adverse reactions to ABO mismatched blood transfusions or organ transplantation and the rejection of xenografts. These clinical effects do not reflect the biological functions of NAbC. However, they launch the possibility of using NAbC for boosting immunity in different clinical settings by means of: 1) expression of glycan antigens in elements that do not hold them to allow the binding and reactivity of existing NAbC; 2) removal of existing NAbC; 3) manipulation of the glycosylation pattern of NAbC.