When mice treated with 22D1 mAb were inoculated i.p. with HK-C. albicans, oxidative burst by rpMϕ was significantly reduced (Fig. 4D middle and right panels), demonstrating that SIGNR1 plays a role in oxidative burst Selleck Silmitasertib at least in rpMϕ. To confirm the interaction of SIGNR1 with Dectin-1 in rpMϕ, we stained the cells with specific Ab before and after the addition of HK- or live C. albicans. Co-localization of SIGNR1 and Dectin-1 was very limited without microbes, but their accumulation at the contact site with HK- and live microbes

on phagosomal membrane was observed (Fig. 5A). Physical association of these two molecules was also detected only when rpMϕ were stimulated (Fig. 5B), and such an association was shown to

be induced rapidly (Fig. 5C). To explore the role of SIGNR1 in C. albicans recognition, we prepared sSIGNR1 and sDectin-1 tetramers, instead of the previously formed Dectin1-Ig-fusion proteins 9, 24. Thermal treatment of sSIGNR1 with Strep-Tactin at 37°C enhanced binding activity. This result may be due to the aggregation of SIGNR1 via its long neck domain (116 amino acids), which contains a heptad-repeat sequence, leading to increased ligand affinity and specificity, as previously reported 22, 25. Our study and several other reports indicate that Dectin-1 and TLR2 MLN8237 recognize microbial components and induce inflammatory responses in either a cooperative 15, 29, 30 or independent manner 13, 14. In RAW-control cells, zymosan induced weak oxidative burst, but TLR ligand-depleted zymosan and PAM3CSK4 did not. By contrast, TLR ligand-depleted zymosan induced a significant

oxidative burst in RAW-SIGNR1 cells, and this response was not enhanced by PAM3CSK4. In addition, TLR2 blocking mAb had no effect on their oxidative burst in RAW-SIGNR1 cells. Based on these results, TLR2 is not largely involved in the oxidative burst response. SIGNR1 was shown to enhance the intracellular oxidative burst of rpMϕ in response to HK-C. albicans. Such an enhancement was due to the recognition of microbes via CRD, since RAW-SIGNR1 cells lacking CRD function were unable to elevate the response. In addition, binding/capture of microbes by SIGNR1 was demonstrated to be crucial for the enhanced oxidative response by the experiment titrating the number of microbes Calpain during the culture. Dectin-1-specific inhibitors, such as laminarin and anti-Dectin-1 mAb, blocked the oxidative response in RAW-control cells, whereas these reagents by themselves showed no effect on the response in RAW-SIGNR1 cells. However, they were able to inhibit the response in cooperation with reagents to SIGNR1, as previously reported in the case of zymosan binding in rpMϕ 23. In addition, piceatannol, a Syk-specific inhibitor, totally blocked the response in not only the RAW-control but also RAW-SIGNR1 cells, demonstrating that the SIGNR1-dependent enhanced response relies on the Syk-mediated signaling pathway.