PDCD1 and neoplasm: To investigate the functional importance of SEMA3A in affecting T cell immunity in vivo, we used conditional knockout of Nrp1. Prior studies in the B16.F10 tumor model demonstrated that anti-NRP1 antibodies enhance CD8+ T cell infiltration and reduce tumor growth, but that knockout of NRP1 only in CD8 T cells had an effect only when combined with anti-PD-1 antibodies26.