PDCD1LG2 and neoplasm: On the other hand, PD-L2 can be expressed by macrophages, the tumour cells, and the stroma at the TME.50,52 The lack of commercially-available antibodies for these checkpoint molecules for canine neoplasms has limited our ability to localize PD axis molecules within the TME, and thus further studies are needed to determine PD-L2 expression and assess its contribution to malignant features of the tumour.