Tim-3 and PD-1 are powerful immunoinhibitory molecules involved in immune tolerance, autoimmune responses, and antitumor or antiviral immune evasion. A current model for Tim-3 regulation during immune responses suggests a divergent function, such that Tim-3 acts synergistically with TLR signaling pathways in innate immune cells to promote inflammation, yet the same molecule terminates Th1 immunity in adaptive immune cells. To better understand how Tim-3 might be functioning in innate immune responses, we examined the kinetics of Tim-3 expression in human CD14 + M/M 4 in relation to expression of IL-12, a key cytokine in the transition of innate to adaptive immunity. Here, we show that Tim-3 is constitutively expressed on unstimulated peripheral blood CD14 + monocytes but decreases rapidly upon TLR stimulation. Conversely, IL-12 expression is low in these cells but increases rapidly in CD14 + M/M.J, in correlation with the decrease in Tim-3. Blocking Tim-3 signaling or silencing Tim-3 expression led to a significant increase in TLR-mediated IL-12 production, as well as a decrease in activation-induced up-regula-tion of the immunoinhibitor, PD-1; TNF-a production was not altered significantly, but IL-10 production was increased. These results suggest that Tim-3 has a role as a regulator of pro- and anti-inflammatory innate immune responses.