TBX21 and neoplasm: ,48 We found that Tbet+ICOS+ Th1-like CD4+ T cells expressed the highest level of PD-1 among tumor-infiltrating CD4+ Tconv (Figure 2M), indicative of high tumor reactivity,49 and that in vivo treatment with 9D9 increased the proportion of PD-1+ CD4+ T cells producing IFNγ upon re-stimulation ex vivo (Figure 2N).