CD4 and neoplasm: Again, ovalbumin-specific OT-II TCRtg CD4+ T cells were able to eradicate ovalbumin-expressing MHC-deficient HCmel12 Jak1-KO tumours, whereas ovalbumin-specific OT-I TCRtg CD8+ T cells were ineffective (Fig. 1r and Extended Data Fig. 3h,i).