Tissue resident memory T cells (TRM)

Published on July 25, 2022   30 min

Other Talks in the Series: The Immune System - Key Concepts and Questions

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Good day. My name is Marc Veldhoen. I'm a professor of immunology at Lisbon University in Portugal. Today's subject is tissue resident memory cells. We will get a closer look at how they are defined, how they develop, and what uses they have.
I'm going to limit myself to CD8 T cells. These are the most defined tissue resident memory cells. These are the cells that provide protection against infections by intracellular pathogens. The most common are viruses and bacteria, but also protozoan parasites. Think about the malaria parasite. Lastly, and not unimportantly, they also provide protection against tumours. We will go into that a little bit later.
There are two main T cell subsets, CD4 T cells and CD8 T cells. Importantly, CD8 T cells get antigens presented to them in MHC class I molecules, that's how they get activated. CD4 T cells get presented through the antigens in MHC class II molecules.
The two main T cell subsets pick up antigens from different cell types. Any cell in your body expresses MHC class I because every cell in your body can get infected. These can be recognised by CD8 T cells. CD4 T cells get presented when things are eaten by antigen-presenting (APCs). These constantly eat, bounce off their environment and present themselves before T cells. Now, I'm going to focus on CD8 T cells, but CD4 T cells will play a role because they are really the orchestrators of immune responses.
Just a reminder that, during an activation, a T cell needs several signals. Otherwise, nothing will happen. The interaction between an MHC molecule, a peptide and a T-cell receptor does not result in activation. This would be too dangerous, you will need more signals. Signal 2 comes from co-stimulatory molecules, of which there are a whole bundle. We will not go into that today at all. That results in the stabilisation of the signal and proliferation of T cells.