GFAP and brain injury: Indeed, S100B and GFAP leak from injured astrocytes, H-FABP leaks from endothelial cells and neuron cell bodies, whereas Il-10 is expressed by monocytes and macrophages.[8, 11–14, 42, 43] The difficulty, for all biomarker research for brain injuries, is to know if the measured proteins really originate from the brain injury.