Immunity system complexity: how T cells are triggered (Introduction)

by David Turell , Wednesday, October 25, 2023, 16:27 (185 days ago) @ David Turell

Another review:

https://mail.google.com/mail/u/0/#inbox/FMfcgzGwHLpZKlgNVsFxBpMRkFrvFbrL

"When a foreign substance enters the body, it puts the immune system on high alert. Helper T cells sound the alarm, prompting their deadlier relatives—the so-called killer T cells—to go on the offensive. To make sure these warriors don’t go too far, regulatory T cells (Tregs) tamp down inflammation and try to prevent the immune system from attacking the body’s own tissues.

"Once an infection has cleared, some immune cells stick around the lymph node and become memory T cells, which can quickly mobilize if they’re exposed to the same pathogen again in the future. Both helper and killer T cells can turn into memory T cells, but until recently, scientists didn't know much about the behavior of Tregs, and whether they, too, hang out in lymph nodes for long periods of time. It turns out they do, according to research published in Science Immunology. And this newly described population of memory-like Tregs could open new potential avenues for fine-tuning a person’s immune activity and reducing inflammation in chronic immune conditions.

***

"...while most Tregs leave the structures post-infection, up to 20% can remain in the same lymph node for weeks to months. These ‘resident’ Tregs behaved differently from their circulating counterparts and resembled memory T cells found in other tissues."

The actual paper abstract:

https://www.science.org/doi/10.1126/sciimmunol.adj5789?utm_source=sfmc&utm_medium=e...

"Regulatory T cells (Treg) are present in lymphoid and non-lymphoid tissues where they restrict immune activation, prevent autoimmunity and regulate inflammation. Treg in non-lymphoid tissues are typically resident, while those in lymph nodes (LNs) are considered to recirculate. However, Treg in LNs are not a homogenous population and circulation kinetics of different Treg subsets are poorly characterized. Furthermore, whether Treg can acquire memory T cell properties and persist for extended periods after their activation in LNs is unclear. Here, we used in situ labeling with a stabilized photoconvertible protein to uncover turnover rates of Treg in LNs in vivo. We found that while the majority of Treg in LNs recirculate, 10–20% are memory-like resident cells that remain in their respective LNs for weeks to months. Single cell RNA sequencing revealed that LN-resident cells are a functionally and ontogenetically heterogeneous population and share the same core residency gene signature with conventional CD4+ and CD8+ T cells. Resident cells in LNs did not actively proliferate and did not require continuous TCR signaling for their residency. Yet, resident and circulating Treg had distinct TCR repertoires, and each LN contained exclusive clonal subpopulations of resident Treg. Our results demonstrate that, similar to conventional T cells, Treg can form resident memory-like populations in LNs after adaptive immune responses. Specific and local suppression of immune responses by resident Treg in draining LNs might provide new therapeutic opportunities for the treatment of local chronic inflammatory conditions."

Comment: this sophisticated array of differentiated T cells with purposeful integration reeks of design. Not by the chance mutation of Darwin theory.