Expression of P2X7R in tumour versus ‘peri- tumour’. P2X7R expression was measured using immunohistochemistry against P2X7R protein. The degree of fluorescence intensity (standardized to background fluorescence intensity) in each cell was used as an indication of P2X7R expression. A. P2X7R expression was increased in microglia derived from tumour versus ‘peri-tumour’ tissue. n = 517 cells from 4 human glioma (tumour) and respective ‘peri-tumour’ tissue. Insets above the graph show representative images of microglia expressing P2X7R. Red = microglial marker isolectin GS-IB4. Green = P2X7R expression. Scale bar, 20 μm. B. P2X7R expression was conversely increased in ‘peri-tumour’ glioma cells compared to glioma cells derived from the core of the tumour. n = 551 cells from 3 human glioma tumour and respective ‘peri-tumour’ tissue. Insets above the graph show representative images of glioma cells expressing P2X7R. Red = glioma cell marker, GFAP, Green = P2X7R expression. Scale bar, 20 μm.