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What Is Cross-Reactivity?

J. Finnegan
J. Finnegan

Cross-reactivity is the ability of an immune cell to attack a foreign cell that's different from the one that created it. Immune cells are made by the body to destroy disease-causing substances. Each immune cell attacks a certain type of invasive agent. If a different type of disease-causing substance has similar chemical properties to a previously encountered invasive agent, then cross-reactivity can occur allowing the immune cell to attack the new invader. This process is also known as cross-immunity and cross-protective immunity.

A pathogen is a disease-causing agent such as a virus, bacteria, parasite, or fungus. When a pathogen enters the body, its presence triggers the innate immune system. The response of the innate immune system is general, but often sufficient to fight off most pathogens. If the response of the innate immune system isn't enough to fend off the body's invaders, the adaptive immune system is triggered, and it mounts a specified attack.

Immune cells are created by the body to destroy disease-causing substances.
Immune cells are created by the body to destroy disease-causing substances.

All jawed vertebrates, including humans, have an adaptive immune system. It differs from the simpler innate immune system in that its response to a pathogen is very specific. The adaptive immune system is able to recognize proteins, or antigens, on the surface of the pathogenic cells and create an immune cell, or antibody, specifically designed to destroy it.

Cross-reactivity may apply to those who suffer from allergies.
Cross-reactivity may apply to those who suffer from allergies.

Sometimes a different pathogen will have proteins that are the same or similar to the ones on a pathogen the body has already encountered. The adaptive immune system recognizes the antigen and uses already created antibodies to attack it, thereby destroying the new pathogen. This process is called cross-reactivity.

The term cross-reactivity also applies to allergy suffers. The immune system goes through the same process, however, the antigen causing it isn't pathogenic, but the body perceives it to be a potentially dangerous or disease-causing threat. In this scenario the antigen is called an allergen.

Some people may only experience nasal pain and pressure from an allergic reaction while others develop hives or eczema.
Some people may only experience nasal pain and pressure from an allergic reaction while others develop hives or eczema.

Any substance that causes an allergic reaction is an allergen. Allergic reactions vary highly in both severity and presentation. Allergy sufferers who are allergic to the same substance can produce different reactions to it. For example, one person who is allergic to grass will suffer from nasal congestion, while another will get a skin rash. Allergic reactions are the side effects of the immune system attacking an allergen.

Exposure to certain allergens may cause some people to experience intense itching.
Exposure to certain allergens may cause some people to experience intense itching.

Allergen-induced cross-reactivity can occur when the body is exposed to similar or closely related allergens. For example, people who are allergic to birch pollen should avoid eating raw apples because they have similar chemical compounds. The immune cells recognize a similarity in the chemical composition of the nonallergenic substance and attack it, causing a cross-reactive allergy.

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    • Immune cells are created by the body to destroy disease-causing substances.
      By: robyelo357
      Immune cells are created by the body to destroy disease-causing substances.
    • Cross-reactivity may apply to those who suffer from allergies.
      By: FedeCandoniPhoto
      Cross-reactivity may apply to those who suffer from allergies.
    • Some people may only experience nasal pain and pressure from an allergic reaction while others develop hives or eczema.
      By: bsites
      Some people may only experience nasal pain and pressure from an allergic reaction while others develop hives or eczema.
    • Exposure to certain allergens may cause some people to experience intense itching.
      By: Dmitry Lobanov
      Exposure to certain allergens may cause some people to experience intense itching.