Final answer:
Dolichos biflorus is used to neutralize antibodies to P1, aiding in correct blood typing by preventing antibody-mediated agglutination.
Step-by-step explanation:
The substance used to neutralize antibodies to P1 (also known as lectins) is Dolichos biflorus. This particular substance is used in blood typing and to identify specific blood group antigens. The substance works by neutralizing or inhibiting antibodies that would cause agglutination, thus permitting accurate blood typing. Neutralization involves the binding of antibodies, such as IgG, IgM, or IgA, to epitopes on the surface of pathogens or toxins, preventing their harmful effects. For example, secretory IgA is secreted into mucus, tears, saliva, and colostrum and can neutralize toxins through opsonization, which is a process where the pathogen is marked for destruction by the immune cells.