The formation of memory T helper type 1 (Th1) cells is currently explained by a linear differentiation pathway, as defined by the transition from IFN-γ producing Th1 cells to resting memory cells. However, in August 12 advanced online Nature Immunology, Chang-you Wu and colleagues at the National Institutes of Health, Bethesda, US, show that distinct lineages of Th1 cells have differential capacities for memory cell generation in vivo, supporting a revised model of Th1 memory differentiation (Nat Immunol 2002, DOI:10.1038/ni832).

Wu et al. studied the long-term maintenance of distinct populations of Th1-lineage cells in vivo and observed that effector Th1, IFN-γ producing cells are short-lived and do not efficiently develop into long-term memory TH1 cells. In contrast, a population of activated Th1-lineage cells that did not secrete IFN-γ after primary antigenic stimulation persisted for several months in vivo and developed the capacity to secrete...