Correlating the labelling index of PD-L1 positive TAFs and labelling index of PD-1 positive subepithelial inflammatory T-lymphocytes in oral leukoplakia, the Pearson correlation coefficient of 0.358 indicated a moderate positive correlation which was found to be statistically non-significant (p value: 0.079) (Table 4). This evidence concerns the gene PDCD1 and Oral leukoplakia.