PDCD1LG2 and neoplasm: Furthermore, PD-L1 was expressed on a large fraction of B16ova tumor cells (wt: 70.3% ± 4.6%; Cblb−/−: 84.7% ± 4.3%), whereas PD-L2 was barely detectable (wt: 0.3% ± 0.1%; Cblb−/−: 0.6% ± 0.2%) (n = 6).