How protective immunological memory arises at mucosal sites is reported online this week in Nature Immunology.
Many pathogens enter the body at mucosal sites, mainly the tissues that line the gut and respiratory tract. A long-term goal has been to understand how to generate effective memory at these sites.
Hilde Cheroutre and colleagues identify a molecule called TL that influences selection of memory T cells. TL is expressed on the surface of gut epithelial cells where it interacts with T cells. Surprisingly, TL induces cell death of these cells, unless they express another surface molecule CD8alpha-alpha. Expression of CD8alpha-alpha is induced by T cell activation — and higher affinity cells express more CD8alpha-alpha. Hence the TL-CD8alpha-alpha interaction serves as a means to select for more effective memory T cells that patrol mucosal tissues.