PD-1 mRNA levels in peripheral blood nuclear cells of CHB were sequentially decreased from rs10204525 genotypes AA, AG to GG.[24] Subjects with genotype AA of PD-1 rs10204525 had higher PD-1 expressions in tumor tissues, peritumor tissues, and cirrhotic tissues than with other genotypes.[25] With lower inhibitory PD-1 expression, the immune system may show greater anti-virus function, and the individual may not easily get infected. Here, PDCD1 is linked to neoplasm.