TI - Results and discussion beta-glucan microparticles are weak inducers of Dectin-1 -dependent cytokines . AB - Different particulate beta-glucans have been used to study signalling by Dectin-1 in MPhi and DC . Some investigators , including ourselves , have previously utilized curdlan , a large particulate ( 1,3 ) -beta-glucan from Alcaligenes faecalis16 , to demonstrate that triggering of the Dectin-1/Syk pathway independently of TLR signalling promotes DC activation , including secretion of cytokines such as IL-6 , TNF-alpha , IL-2 , IL-10 and IL-12p40 7 , 17 . Others have used beta-glucan microparticles ( Glu-mp ) , a highly purified microparticulate form of ( 1,3 ) -beta - d-glucan from Saccharomyces cerevisiae , to stimulate MPhi 3 , 18 , 19 . In those cells , Glu-mp induces phosphorylaTION of both Syk kinase and its SUBstrate SLP-76 but does not lead to cytokine and chemokine production 3 . However , Glu-mp potently synergises with TLR agonists in promoting the activation of NF-kappaB and the production of TNF-alpha , MIP-1alpha and MIP-2 3 . These studies suggested that distinct types of beta-glucan vary in their ability to trigger Dectin-1 -dependent innate responses and/or that DC and MPhi possess intrinsically distinct responses to Dectin-1 engagement . To test the former hypothesis , we compared the ability of Glu-mp and curdlan with activate DC , using production of inflammatory cytokines as the major readout . First , we confirmed that , like curdlan 7 , Glu-mp preparations acted as specific ligands for Dectin-1 . We found that fluorescent Glu-mp binds to Dectin-1 -transfected HEK293 cells but not to the parental cell line ( Fig 1A , left ) . In addition , fluorescent Glu-mp bound to WT bone-marrow-derived DC ( BMDC ) but not to cells derived from Dectin-1-deficient mice , indicating that DC do not possess compensatory receptors for binding beta-glucans ( Fig 1A , right ) . To directly compare the ability of curdlan and Glu-mp preparations to stimulate DC , cells were cultured with curdlan or Glu-mp and the levels of IL-6 , IL-2 , TNF-alpha and IL-12p40 in supernatants were measured after 16 h . Glu-mp induced much lower levels of cytokines when compared with curdlan ( Fig 1B ) . Extensive titration studies established that even when used at maximal dose , Glu-mp induced at best one-hundredth to one-tenth the amount of TNF-alpha and IL-6 that could be elicited by an optimal dose of curdlan ( Fig 1B ) . Thus , Glu-mp is markedly weaker than curdlan at stimulating DC . This is consistent with the data obtained with MPhi 3 and therefore suggests that the differences previously noted for Glu-mp and curdlan are not only attributable to the use of different cell types 3 , 7 .