ITGA4 and glioblastoma: We then dissected the contribution of resident vs. blood-derived macrophages in the CD33high cells as reported previously (24) and identified BMDM as CD45+/CD33high/HLA-DR+/CD49d+ cells and microglia (MG) as CD45+/CD33high/HLA-DR+/CD49d- (Figure 1C), and observed a higher frequency of BMDM in GBM compared to BrM (Figure 1D, median 16.3% in BrM vs. 47.3% in GBM, P = 0.003).