Staying alive--naïve CD4(+) T cell homeostasis.

The immune system must maintain a broad repertoire of naïve T cells in order to respond to the diverse range of pathogens that it will encounter over the course of a lifetime. Although it is known that contact with IL-7 is crucial for the survival of naïve T cells, the precise intracellular signals that mediate its effects remain obscure. An article in this issue of the European Journal of Immunology has found that IL-7 requires the coordinated action of multiple pathways to maintain naïve CD4(+) T cells.