Summary
Central and peripheral mechanisms eliminate or suppress self-reactive lymphocytes to prevent autoimmunity.
In depth
Central tolerance: deletion in thymus and bone marrow. Peripheral tolerance: anergy, regulatory T cells (FOXP3) and immune privileged sites. AIRE gene expresses tissue antigens in the thymus.
Tolerance mechanisms are imperfect, so low-level autoreactive cells exist. Regulatory T cells and inhibitory receptors keep them in check.
Key idea: tolerance prevents the immune system from attacking the self.
The thymic protein AIRE drives expression of tissue-specific antigens so that T cells reacting to them are deleted; defects cause the autoimmune syndrome APECED. Peripheral mechanisms include ignorance (hidden antigens), anergy, suppression by Tregs, and deletion by activation-induced cell death. Immune privileged sites (eye, brain, testis) restrict immune access.
Oral tolerance means eating an antigen can reduce responses to it, used in allergy prevention. In pregnancy, the foetus is tolerated through placental barriers and Tregs. Tolerance breaks in autoimmune disease, and inducing tolerance is a goal for transplants and allergy (allergen immunotherapy).
Example: IPEX syndrome results from FOXP3 mutations that remove Tregs and lead to severe autoimmunity.
Frequently asked questions
What is Immunological Tolerance?
Central and peripheral mechanisms eliminate or suppress self-reactive lymphocytes to prevent autoimmunity.
Which area of biology covers Immunological Tolerance, and how advanced is it?
Immunological Tolerance is one of the 52 topics in Immunology & Disease. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include T Lymphocytes, Immune System, Autoimmune Disease.
Can you give an example of Immunological Tolerance?
AIRE mutations cause autoimmune polyendocrine syndrome.
What should I learn before Immunological Tolerance?
Work through the Beginner topics in Immunology & Disease first, such as Immune System, Viruses, Innate Immunity, then return to Immunological Tolerance. Advanced topics assume the Intermediate vocabulary.
What topics are related to Immunological Tolerance?
The closest topics to Immunological Tolerance are T Lymphocytes, Immune System, Autoimmune Disease, Cytokines. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Immunological Tolerance?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Immunological Tolerance. To practise the whole of Immunology & Disease, use the Immunology & Disease quiz.
How is Immunological Tolerance different from T Lymphocytes?
Immunological Tolerance: Central and peripheral mechanisms eliminate or suppress self-reactive lymphocytes to prevent autoimmunity. T Lymphocytes: Cells that mature in the thymus; helper T cells coordinate immunity and cytotoxic T cells kill infected cells. Read both side by side and note what each one explains.
How should I study Immunological Tolerance step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with T Lymphocytes and explain the difference aloud. Finally, take the Immunology & Disease quiz and come back to this page for any question you miss.