We next investigated the downstream signaling pathways through which TLR2 induced Raldh2 expression . TLR2 stimulates rapid induction of ERK , which mediates IL-10 production by DCs16,18,23 . Induction of Raldh2 mRNA expression was largely abrogated by inhibitors against ERK ( Fig . 1h ) . Additionally DCs from Erk1 −/− mice had substantially reduced Raldh2 expression upon zymosan stimulation ( data not shown ) . Furthermore , induction of Raldh2 was also inhibited substantially by a syk inhibitor ( data not shown ) . Thus , Raldh2 induction by zymosan is syk - dependent , but largely dectin-1 independent , suggesting that an alternative syk - dependent receptor is likely involved . In summary therefore , zymosan induces Raldh2 expression in DCs via TLR2 - mediated activation of ERK , likely acting in concert with syk - dependent signaling via another receptor .