It was surprising to see a role for TLR2, as, based on results in BMM and epithelial cells, type I IFNs production is usually not known to result from TLR2 signaling [5] [6] [7] [8] . Classical TLR2 signaling leads to NF-kB-dependent production of inflammatory cytokines [21] . However, in support of an unconventional role for TLR2, recent studies reported roles for TLR2-dependent induction of IFN-b in response to vaccinia virus or synthetic ligands [26, 29] . In the vaccinia virus study, a specific inflammatory monocyte population -Ly6C hi -was shown to be the source of IFNb [26] . In the present study we show that TLR2-dependent IFN-b synthesis is a property of both resident and recruited inflammatory PEM. Furthermore, the two previous studies documented that TLR2 activation of type I IFN responses to TLR ligands occurs within intracellular compartments, and that TLR2 signals from the phagosome in response to viral infection or synthetic TLR2 ligands [26, 29] . These results challenged the view that TLR2 signals solely from the plasma membrane. In our experiments, pretreatment of PEM with either cytochalasin D, an inhibitor of actin polymerization and thus internalization, dynasore, an inhibitor of the endocytic effector dynamin, or chloroquine, which inhibits endosome acidification [30, 31] , significantly impaired the induction of IFN-b following Listeria infection, strongly suggesting that phagocytosis of L. monocytogenes and intracellular location of TLR2 trigger this response. These observations also correlate with our early hypothesis that the inflammatory response induced by DpgdA is due to an enhanced release or accessibility of bacterial cell wall components to TLR2.