DLL1 and infection: Gata3 ChIP‐seq was carried out on naïve (CD44loCD62Lhi) OTIs, after in vitro activation in the presence of IL‐4 or Notch signaling (OP9‐DL1), or primary effector OT‐Is isolated directly ex vivo 10 days after adoptive transfer and infection with A/HKx31‐OVA (Supplementary figure 1a).