Aglutinogens of the various blood types are classified as what?

Aglutinogens, which are found on the surface of red blood cells, are classified as antigens. These are specific molecules that can trigger an immune response if they are recognized as foreign by the immune system. In the context of blood types, the presence or absence of certain agglutinogens determines a person's blood group (such as A, B, AB, or O). For instance, type A blood has A antigens (agglutinogens) on its red blood cells, while type B blood has B antigens.

The immune system produces antibodies that target these antigens, which is crucial for blood transfusions and organ transplants to avoid adverse reactions. Understanding the nature of agglutinogens as antigens is essential for appreciating how blood compatibility is determined and the implications this has in medical settings.

The other classifications—proteins, enzymes, and hormones—do not accurately describe agglutinogens in this context, as they perform different functions in the body unrelated to the immune response associated with blood types.