Characterization of microglial responses to Staphylococcus aureus: effects on cytokine, costimulatory molecule, and Toll-like receptor expression.

Microglia participate in innate immune responses in the central nervous system (CNS). This work demonstrates that microglia can recognize heat-inactivated Staphylococcus aureus and its cell wall product peptidoglycan (PGN) through the elaboration of numerous proinflammatory cytokines and chemokines. Microglia also exhibited S. aureus bactericidal activity. Microglia constitutively expressed low levels of Toll-like receptor 1 (TLR1), TLR2, TLR6, and CD14, all of which were enhanced following S. aureus exposure. Activation of resident microglia by S. aureus may serve to amplify the CNS antibacterial immune response through the release of cytokines, chemokines, and induction of bactericidal activity.