Immunity system complexity: B & T cell training (Introduction)

by David Turell , Wednesday, June 01, 2022, 19:54 (697 days ago) @ David Turell

A good review of the immune system and autoimmunity:

https://www.sciencedaily.com/releases/2022/05/220531192940.htm

"The immune system, however, faces far greater challenges in distinguishing self from non-self. Should this complex surveillance network fail to identify a foreign intruder, like a bacterium or virus, the result may be serious, unchecked disease.

"Under certain circumstances, however, the immune system can become over-vigilant, identifying our own tissues as foreign and targeting them for destruction, resulting in autoimmune disease. Autoimmune responses are also associated with some cancers.

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"Two primary components of the so-called adaptive immune system also play important roles in autoimmunity. These are the are white blood cells or lymphocytes, known as T cells and B cells. Lymphocytes are crucial for maintaining health and are essential to survival. These sentries, ceaselessly patrolling the bloodstream, are alerted by the presence of foreign entities known as antigens.

"T cells guard against infection from pathogens like bacteria, viruses and fungi. They can also attack and destroy cancerous cells. B cells secrete proteins known as antibodies that either disrupt interactions or target infected cells so that other cells can come in to destroy them. Antibodies operate by binding with pathogens or foreign substances, including toxins, and neutralizing their harmful effects. If an antibody binds with a virus, for example, it may prevent the intruder from entering a normal cell to cause infection. B cells can also recruit other specialized immune cells to migrate to the sites of infected cells and help destroy them.

"The immune system's defensive arsenal is exquisitely sensitive to foreign proteins, peptides, enzyme complexes, RNA and DNA. When these are encountered, B cells can swing into action, producing antibodies directed against these foreign entities.

"The immune system, however, faces a formidable challenge. B and T cells must be able to accurately target threats to the body while remaining harmless to host cells and tissues. Immune cells are not born with this knowledge, they learn it over a matter of weeks, receiving training in a kind of biological classroom, where they undergo two rounds of careful screening.

"The B and T cells that successfully graduate from their training sessions exhibit two kinds of immune tolerance, central immune tolerance, which develops in the bone marrow and peripheral immune tolerance, which matures in the lymph nodes.

"After their training, cells displaying immune tolerance, a kind of non-aggression pact with healthy tissues -- are preserved in the body for future use. Immune cells that flunk out of their training and present a risk of autoimmunity are sequestered or destroyed.

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"The mistaken targeting of self-antigens due to their similarities with disease antigens is known as molecular mimicry and is implicated in many autoimmune disorders, from rheumatoid arthritis to multiple sclerosis.

"The new study explores common autoantibodies -- those occurring in healthy individuals. Though these common autoantibodies don't appear to cause disease, they nevertheless appear in as many as 40% of the people tested. It is likely that at least some of these common autoantibodies have been mistakenly identified as disease antibodies.

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"The blood samples came from healthy individuals of both sexes, ranging in age from infancy to 84 years old. The results showed that the number of autoantibodies increased from birth up to the age of adolescence and then plateaued. Further, the number of autoantibodies detected was the same regardless of sex, a surprising outcome given the large disparity between men and women in the prevalence of autoimmune disease.

"Another underlying enigma is why common autoantibodies fail to produce autoimmune disease. Although such antibodies appear to have evaded the screening process leading to immune tolerance, their occurrence in the body remains benign. It is believed that autoimmune pathology requires autoantibodies to bind and form complexes with autoantigens, and this may be blocked in the case of common autoantibodies.

Comment: this study shows recognizing self from non-self-produced common autoantibodies that are somehow controlled against damaging of the self. The use of the word 'schooling' in describing the training of B and T cells to do their job means recognizing the cells are students in training, no thought on their part involved other than developing memory of what to do, and how to react. The antibody chemicals produced are also automatically created based on the precise antigens the invaders present. A beautiful designed defensive system.