In the current issue of Nature Immunology, Casanova and colleagues demonstrate that humans (and mouse models) with autosomal-recessive SPPL2a deficiency have a severe defect in conventional dendritic cell 2 survival and production of IL-12 and IL-23, and diminished IFN-γ secretion by mycobacterium-specific memory T cells, thus resulting in increased susceptibility to mycobacterial diseases.