- Author:
	        		
		        		
		        		
			        		Doo-Won SONG
			        		
			        		
			        		
			        			1
			        			
			        		
			        		
			        		
			        		
			        		;
		        		
		        		
		        		
			        		Woong-Bin RO
			        		
			        		;
		        		
		        		
		        		
			        		Hee-Myung PARK
			        		
			        		
		        		
		        		
		        		
			        		
			        		Author Information
			        		
 - Publication Type:Original Article
 - From:Journal of Veterinary Science 2021;22(5):e75-
 - CountryRepublic of Korea
 - Language:English
 - 
		        	Abstract:
			       	
			       		
				        
				        	Background:Programmed cell death protein-1 (PD-1) and programmed cell death ligand-1 (PD-L1) have important roles in tumor evasion of the immune system. 
				        	
Objectives:This study aimed to assess the diagnostic utility of circulating PD-1 and PD-L1 levels in healthy dogs and dogs with tumors.
Methods:Circulating PD-1 and PD-L1 levels in the serum of 71 dogs with tumors were compared with those of 52 healthy dogs by performing enzyme-linked immunosorbent assay (ELISA).
Results:The ELISA results revealed higher circulating PD-1 and PD-L1 levels in dogs with tumors (2.9 [2.2–3.7] ng/mL; median [IQR] and 2.4 [1.4–4.4] ng/mL, respectively) than in healthy dogs (2.4 [1.9–3.0] ng/mL; p = 0.012 and 1.4 [0.9–2.1] ng/mL; p < 0.001, respectively). Especially, there was a significant difference in circulating PD-1 levels between healthy dogs and dogs with malignant epithelial tumors (2.4 [1.9–3.0] ng/mL and 3.1 [2.6–4.4] ng/mL, respectively; p < 0.01). In addition, there was a significant difference in circulating PD-L1 levels between healthy dogs and dogs with lymphomas (1.4 [0.9–2.1] ng/mL and 2.7 [1.6–5.8] ng/mL, respectively; p < 0.001).
Conclusion:This study indicates that circulating PD-1 and PD-L1 have potential as tumor diagnostic biomarkers in dogs with tumors. 
            
