CD44 and neoplasm: To investigate the percentage and characteristics of PD-1+ TIL in tumor microenvironment, CT26, B16-F10 tumor tissues were made into single cell suspension and stained with CD45-APC, CD4-FITC, CD8-PE/Cy7, PD-1-PE, CD44-PE/Cy5.5 and CD62L-APC/Cy7 flow antibodies to analyze the percentage of CD4+PD-1+ and CD8+PD-1+ TIL.