CHI3L1 and bipolar disorder: Therefore, we previously investigated a set of immune biomarkers in cerebrospinal fluid (CSF) in bipolar disorder and healthy controls, including monocyte chemoattractant protein-1 (MCP-1), chitinase-3-like protein-1 (YKL-40), soluble cluster of differentiation 14 (sCD14), tissue inhibitor of metalloproteinases-1/2 (TIMP-1 and TIMP-2), and interleukin 8 (IL-8)20,21.