Increased interferon gamma expression is associated with T-cell brain infiltration and activated microglia with increased blood–brain barrier permeability.62 YKL-40 is also upregulated in several neurological disorders, and during neuroinflammatory processes it is overexpressed in reactive astrocytes and microglial cells.63 The association between pro-inflammatory cytokine levels and regional microglial activation suggest that blood-based biomarkers of inflammation might be able to capture inflammatory processes that are relevant for central inflammation and brain changes. This evidence concerns the gene CHI3L1 and nervous system disorder.