CD38 and glioma: The PD-L1 expression level in GBM glioma appears to be preserved by the presence of CD8+ T cells, which presumably limits the effectiveness of CCR5+CD38+HLA-DR+CD8+ TILs; therefore, the availability of CCR5+CD38+HLA-DR+CD8+ T cells in term of numbers to initiate proper immune responses may also be violated and insufficient.