Moreover, mRNA expressions of both PD-1 and PD-L1 were detected in tumor lesions of MDV-infected chickens by nested RT-PCR using laser-captured microdissections, and mRNA expression of PD-1 was positively correlated with mRNA expression of Meq [26], suggesting a higher expression of PD-1 in tumor cells. The gene discussed is PDCD1; the disease is neoplasm.