Immunity system complexity: keeping T cells ageless (Introduction)

by David Turell , Thursday, September 15, 2022, 18:36 (589 days ago) @ David Turell

It involves exchanging telomeres:

https://medicalxpress.com/news/2022-09-mechanism-life-immune.html

"Each of the chromosomes, present in all cells, contains a protective cap called a telomere; a specific DNA sequence that is repeated thousands of times. The sequence has two purposes: first, it protects the coding regions of the chromosomes and prevents them from being damaged, and second, it acts as an aging clock that controls the number of replications (also known as divisions) a cell can make.

"In T cells (a type of white blood or immune cell), along with most cells, the telomeres become shorter and shorter (telomere attrition) with each subsequent cell division. Once telomeres reach a critically short length, the cell ceases to divide and enters senescence—the process of being disposed by the immune system, or persist in an altered, dysfunctional state.

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"In the study, researchers initiated an immune response of T-lymphocytes against a microbe (foreign infection). Unexpectedly, they observed a telomere transfer reaction between two types of white blood cells, in extracellular vesicles (small particles that facilitate intercellular communication). An antigen presenting cell (APC), consisting either of B cells, dendritic cells or macrophages, functioned as a telomere donor, to the T lymphocyte—the telomere recipient cell. Upon transfer of the telomeres, the recipient T cell became long-lived and possessed memory and stem cell attributes, enabling the T cell to protect a host against a lethal infection in the long term.

"The telomere transfer reaction extended certain telomeres about 30 times more than extension exerted by telomerase. Telomerase is the single DNA synthesizing enzyme that is devoted to telomere maintenance in stem cells, cells of the immune systems and found in fetal tissue, reproductive cells and sperm. However, it does not provide this function in other cells, leading to telomere attrition. Even in immune cells where the enzyme is naturally active, continuous immune reactions cause progressive telomerase inactivation leading to telomere shortening, when cells stop dividing, and replicative senescence occurs.

"Professor Lanna added, "The telomere transfer reaction between immune cells adds to the Nobel-prize winning discovery of telomerase and shows that cells are capable of exchanging telomeres as a way to regulate chromosome length before telomerase action begins. It is possible that aging may be slowed down or cured simply by transferring telomeres."

Comment: the immune system must be constantly on the alert for infection. It is logical aging of T cells should be prevented. Once again it is obvious natural evolution based on chance can't do this easily. Design is required.