T-cells work away from home

T-cells are key components of the body’s immune system that are produced by lymphoid organs and subsequently move to the surrounding tissues to target viruses. Now Francis Carbone at the University of Melbourne and co-workers¹ have discovered that T-cells in the non-lymphoid tissue not only remember previous infections, but can generate a sophisticated local response to secondary infections. The process works in combination with dendritic cells that catch the virus and present it to the T-cells.

It was previously thought that T-cells in non-lymphoid tissue served only a simple search-and-kill effector function and were replenished from the circulation when needed. To test this notion the researchers extracted nerve tissues from mice, weeks after the mice had been infected with the herpes virus. The nerve tissues, containing T-cells, were transplanted into different mice. When herpes was activated in the second group of mice, the number of herpes-specific T-cells rose rapidly due to cell division that was confined completely to the local environment. This implies the presence of fully responsive ‘memory’ T-cells outside the circulation that remembered the first infection.

Dendritic cells were recruited from blood to the site of infection, which took time, causing a delay in T-cell activation. This lag was long enough to allow herpes to briefly escape immune control.