CD8A and primary central nervous system lymphoma: It was found that the baseline of tumour immune response in PCNSL patients was reduced compared to the normal, and in most cases the CSF tests revealed a decrease in CD8+ T cells and helper DC cells, as well as a decrease in Th1 cells and an increase in Th2 cells, suggesting that the microenvironment of PCNSL inhibits the activation of most immune cells (Chang et al., 2015; Takashima et al., 2019a; Monabati et al., 2020).