TREM1 and glioblastoma: Figure 2D illustrates the gating of the double-positive (DP) glioblastoma/host hybrid cells (EGFP+RFP+), isolated from the dissociated brain tissues using a 30% Percoll gradient. The DP cell percentage varied from 1 to 14% and positively correlated with tumor size. TREM1 expression on host cells undergoing glioblastoma/host cell fusion was confirmed on brain slices prepared from the GL261 glioblastoma mouse model (Figure 2E). Around 75% of DP cells, expanded in cell culture and stained with the TREM1 antibody, were TREM1 positive compared to less than 1% of control cells (Figure 2F, G).