What Are the Possible Antigen Types?

An antigen is a type of molecule that triggers a response from the immune system. Typically, the immune system will produce an antibody to fight off the invading substance, either neutralizing or destroying it. Antigens come in many different forms, varying in both purpose and composition. The study of antigens (through immunology) is thus quite intricate.

Haptens

• These little molecules elicit immune system responses when attached to a larger carriers. Carrier molecules most often come in the form of a protein. The covalent bond between these two molecules elicits an immune response that was previously impossible with just the hapten. Urishol, for example, is a hapten allergen secreted by poison ivy onto passing animals. Without oxidation, urishol does not get the attention of the human immune system; yet, with the attachment of oxygen to form quinone, this chemical compound rings the alarm bells for antibodies.

Allergens

• Allergens are well known antigens.

  These famous antigens are substances that cause allergic reactions from the human immune system. Allergens are notable in that only a fraction of the population experiences adverse reactions to them. For these people, the immune system acts in a manner that is a huge overreaction; this all-out attack on "invading" substances hurts the host in the process. Some of the most common allergens are dust, bacteria, pollen, foods, drugs, and synthesized chemicals (colognes). For example, an individual sensitive to dust mites will produce adverse, and possibly fatal, immune reactions when around them.

Superantigens

• Another type of antigen, a superantigen, is one that elicits a huge reaction from the body's immune system. Superantigens operate by stimulating numerous T-cells at once, alarming the immune system and producing various non-specific antibodies to combat the intrusion. In layman terms, superantigens work by confusing the immune system via activating a lot of T-cells. The immune system's careful, specific nature is thrown out of whack through this method. Since superantigens are produced by harmful microbes, treating these infections often requires the removal or destruction of the agent. Scarlet fever and rheumatoid arthritis are associated with superantigen activity.

Mimotopes

• Epitopes are the portion of the invading antigen that the host immune system recognizes. The identification of an antigen epitope triggers a proper response from the body. Mimicking an epitope, thus, could be quite useful in antigen strategy. Mimotopes are macromolecules that mimic an antigen epitope, signaling a swift response to quell the "threat." Mimotopes are used in vaccines so as to adapt the body to the possibility of a specific infection; this keeps the body ready while not harming the host.