CD4 and brain neoplasm: We also evaluated the percentages of CD8+ and CD4+ T cells within the tumour, blood, and spleen and found that anti-PD-1 treatment of EMP3_KO tumour-bearing mice increased IFN-γ-, TNF-α- and IL-2-producing CD8+ and CD4+ T cell infiltration into the brain tumour, blood, and spleen (Fig. 6f-j, Supplementary Fig. 6A-G).