MCAT Content / Immune System / Recognition Of Self Vs Non Self Autoimmune Diseases

Recognition of self vs. non-self, autoimmune diseases

Topic: Immune System

The antigens present on the cells of the body are considered as self-antigens while the antigens that enter the body from the environment are considered as non-self. The lymphocytes of the immune system form antibodies to fight non-self antigens. Sometimes, the lymphocytes create antibodies for self-antigens known as autoantibodies. These can cause autoimmune diseases.

The particles present inside the body are not considered foreign particles and are known as self-antigens as these are the body’s particles. The foreign particles that enter the body from the outside environments are considered by the immune system as harmful and these are known as non-self antigens. The immune system activates lymphocytes to fight against them by producing antibodies. The antibodies against self-antigens are produced only when these antibodies enter the body of another person for which these are non-self antigens such as in mismatch blood transfusion.

When antibodies are formed in a person’s own body against self-antigens, these antibodies are known as autoantibodies. Any disease that results from such an aberrant immune response is termed an autoimmune disease. In other words, the immune system mistakes some part of the body as a pathogen and attacks its cells. Autoimmune diseases are commonly considered complex immune disorders. Coeliac disease, diabetes mellitus type 1 (IDDM), Graves’ disease, rheumatoid arthritis (RA), and allergies are some of the autoimmune diseases.

Practice Questions

Khan Academy

MCAT Official Prep (AAMC)

Biology Question Pack, Vol 2. Passage 12 Question 77

Sample Test B/B Section Passage 2 Question 9


Key Points

• Antigens present on the cells of the body are known as self-antigens while the antigens that enter the body from an external environment are non-self antigens.

• Normally, the lymphocytes of the immune system produce antibodies against non-self antibodies only. These cells do not produce antibodies against self-antigens.

• Autoimmune diseases arise from an immune system that does not function properly and antibodies, known as autoantibodies, are produced against self-antigens.

Key Terms

Antigen: A substance that induces an immune response, usually foreign, but self-antigens and internally produced antigens exist as well.

Autoimmune diseases: Arise from an inappropriate immune response of the body against substances and tissues normally present in the body

Self-antigens: antigens in the body of an individual

Non-self antigens: antigens from outside the body of an individual

Antibody: protein produced in the blood to fight against an antigen

Autoantibody: an antibody produced by the immune system that is directed against one or more of the individual’s proteins, causes autoimmune diseases

Immune system: the system that differentiates self from non-self and protects the body from foreign substances and pathogenic organisms by producing an immune response

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