Memory maintenance

T cells that remember a previously encountered virus are essential in establishing protective immunity. But some T cells have a longer lifetime, and thus effectively a longer immunological memory, than others. Work by Riou et al. (page 79) might explain why effector memory T cells (T_EM) are short lived, whereas central memory T cells (T_CM) are maintained in the body long-term.

The longer-lived T_CM mainly reside in secondary lymphoid organs such as the lymph nodes, whereas the T_EM are found in the peripheral tissues and sites of infection. The exact ontogeny of the two cell types is unknown, but it's thought that T_CM might give rise to the more transient T_EM fighters. Regardless of origin, the biological basis for their different life...