Regulation of IL-10 protein and gene expression in MKK-deficient or p38 inhibitor-treated BMDM. (a) IL-10 protein levels were significantly reduced in MKK3−/− compared with MKK6−/− or WT cells. MKK6-deficiency partially preserved IL-10 expression compared with WT cells. Treatment with the p38 inhibitor significantly decreased IL-10 production in all three groups while JNK or ERK inhibition showed no major effects (*p < 0.05). (b) IL-10 mRNA expression was modestly reduced in MKK3−/− cells compared with WT or MKK6−/− cells. As with protein expression, p38 inhibitor reduced IL-10 mRNA expression in WT, MKK3−/− and MKK6−/− cells but JNK inhibitor showed minimal effect.