Microglial cells and peritoneal macrophages release activin A upon stimulation with Toll-like receptor agonists

Activin A levels are elevated in the cerebrospinal fluid (CSF) of patients with meningitis and in the sera of patients with sepsis. The source(s) of the elevated concentrations of activin A in CSF and serum have not yet been discovered. Here we demonstrate that primary mouse microglial cells and peritoneal macrophages release activin A after treatment with agonists of Toll-like receptor (TLR) 2, 4, and 9. These findings provide further evidence for a role of activin in the innate immune response and suggest that microglial cells and macrophages are a source of elevated activin A concentrations observed in the CSF during bacterial meningitis and in the systemic circulation during sepsis.