We confirmed our previous studies showing that GM-CSF, IL-15, TNF-α and IFN-γ activate human neutrophils inducing these cells to release higher H2O2 levels and fungicidal activity against Pb [17, 18, 37]. However, both H2O2 release and fungicidal activity were not altered after TLR2 or TLR4 blockade showing the non-involvement of these receptors on these neutrophil activities. In agreement with our results, some studies have demonstrated a non-association between TLR2, TLR4 and fungal killing mechanisms. TLR4 was shown to be involved in protection in disseminated candidiasis. However, an association between this receptor and

the mechanisms PF-02341066 in vitro involved in Candida albicans killing, such as nitric oxide and superoxide anion, was not detected [38]. It was also shown that Pb yeasts are recognized by TLR2 and TLR4 resulting in increased phagocytic ability, NO secretion and fungal infection of macrophages. However, this effect did not result in fungal growth control [36]. Our results showing non-TLR2 or non-TLR4 requirement for neutrophil killing mechanisms lead us to ask about the role of other receptors. Some studies have demonstrated the importance of mannose receptors [39, 40] and CR3 [40, 41] in Pb phagocytosis. However, in our study, we learn more can discard mannose receptors

involvement, because this receptor is not expressed by human neutrophils. In contrast, studies have shown CR3 and dectin-1 expression by these cells [42, 43]. Moreover, dectin-1 is involved in C. albicans killing by human neutrophils [35]. Studies are being conducted in our laboratory to test the role of both CR3 and dectin-1 on fungal killing by human neutrophils. We aimed at studying TLR2 and TLR4 requirement for IL-6, TNF-α, IL-8 and IL-10 production. However, in our assays, neutrophils failed to release IL-6 and TNF-α. Studies on the literature are controversial in relation to release

of some cytokines by human neutrophils [44]. However, we are suggesting that lack of TNF-α and IL-6 detection in our assays may be related to the period of culture for supernatant why analysis (at least 18 h). It is possible that this period was very late for TNF-α and IL-6 detection. Neutrophil activation with GM-CSF and TNF-α resulted in a significative increase in IL-8 production, while IL-15 and IFN-γ have no effect. Pb18 also increased IL-8 production. Moreover, there was a tendency towards Pb 18 exhibiting an additive effect in GM-CSF-treated cultures. None of the cytokines activated neutrophils for IL-10 release. This cytokine was only detected after Pb18 challenge. Interestingly, in most assays, cytokines production was inhibited after receptors blockade. However, in relation to this effect, we must consider the most evident role of TLR4 in relation to TLR2. Some studies have shown TLR2 and TLR4 requirement for cytokines production by phagocytic cells in response to several stimuli, including fungi.