CXCL16 contributes to neutrophil recruitment to cerebrospinal fluid in pneumococcal meningitis.

In this study, we analyzed the expression and function of CXCL16 in pneumococcal meningitis. CXCL16 was found to be up‐regulated in RAW264.7 macrophages (but not in neutrophils and endothelial cells) upon pneumococcal stimulation, in the cerebrospinal fluid of patients, and in the brains as well as the cerebrospinal fluid of mice with pneumococcal meningitis. CXCL16 up‐regulation in vivo was dependent on Toll‐like receptor (TLR) 2/TLR4 and MyD88 signaling. Neutralization of CXCL16 in animals before intracisternal pneumococcal infection (using anti‐CXCL16 antibodies) resulted in reduced cerebrospinal fluid pleocytosis. In vitro, murine neutrophils expressed the CXCL16 receptor CXCR6 and showed dose‐dependant migration toward a CXCL16 gradient. Thus, this study implicates CXCL16 as an additional neutrophil chemoattractant in cerebrospinal fluid in early pneumococcal meningitis.