PDCD1 and glioblastoma: We developed 3 mass cytometry panels focused on interrogating immune abundance, checkpoint receptor expression, and protein phosphorylation in tumor-infiltrating lymphocytes, M1-like and M2-like monocyte-derived macrophages, and tissue-resident microglia, focusing on targetable immune receptors (e.g., programmed cell death 1 [PD-1] and T cell immunoreceptor with Ig and ITIM domains [TIGIT]) to test the hypothesis that the immune microenvironment of C-GBM tumors is more immunosuppressed.