Separating Immune Cell Fate

[antigen]

The adaptive immune response is mediated in part by CD8+ T cells,
which protect against intracellular infection by pathogens and against
some tumors. This T cell population fulfills a dual function by
providing immediate protection via effector cells and retaining this
protective immunity long-term, via memory cells. On infection, naïve T
cells carrying pathogen-specific T cell receptors (TCR) differentiate
into short-lived effector cells and long-lived memory cells. However,
it is unclear how this is regulated, and whether memory cells are
formed from the effector cells or differentiate separately . Teixeiro
et al.have now shown a direct role for the TCR specifically in CD8+
memory T cell differentiation. Upon bacterial infection of mice
harboring defective TCRs, mutant T cells were still able to generate
effector T cells and a robust primary immune response, but were
specifically impaired in developing memory T cells. Thus, the
differentiation of effector and memory CD8+ T cells are separable, and
determined by the induction of a distinct set of TCR signals. However,
Bannard et al. (p. 505) used a transgenic mouse line to closely map
the cell fate of a subset of effector T cells that were generated
during the primary response to infection by influenza. These effector
cells were found to survive and become memory cells that could
replicate and expand during secondary infection.


http://www.sciencemag.org/cgi/content/short/323/5913/502