Stepping up Th1 immunity to control phagosomal bacteria.

How does the immune system tailor effector function to particular threats? Krueger et al. reveal that infection with Salmonella enterica (SE), but not with influenza A virus (IAV), drives interleukin (IL)-12-dependent outgrowth of interferon (IFN)-γhi type 1 T helper (Th1) cells, leading to superior protection against this phagosomal pathogen. Among these cells are ZEB2-dependent cytotoxic Th1 cells marked by CX3CR1 expression.