To determine whether the CTL response eradicated leukemia cells that had engrafted in vivo, we transplanted 3 × 104 MLL/AF9-OVA leukemia cells into either wild-type recipients (n = 5) or Rag2-/- recipients (n = 5), which lack adaptive immunity (Fig 2B, Exp. The gene discussed is RAG2; the disease is leukemia.