Intelectin can be an extracellular animal lectin found in chordata. intelectin-1 was not a glycosylphosphatidylinositol-anchored membrane protein. Intelectin-1-transfected cells captured BCG more than untransfected cells and the BCG adherence was inhibited by an inhibitory saccharide of intelectin-1. Intelectin-1-preincubated cells took up BCG more than untreated cells but the adhesion of intelectin-1-bound BCG was the same as that of untreated BCG. Mouse macrophages phagocytosed BCG more efficiently in medium made up of mouse intelectin-1 than in control medium. These results indicate that intelectin is usually a host defense lectin that assists phagocytic clearance of microorganisms. made up of galactofuranosyl residues (Tsuji et al. 2001). Galactofuranosyl residues which are not found on mammalian tissues are contained in the cell walls of various microorganisms including (Daffe et al. 1993) (Pedersen and Turco 2003) (Abeygunawardana et al. 1991) (Leitao et al. 2003) (Suzuki et al. 1997). Furthermore mRNA expression of intelectin increases during immune responses such as in infections (Pemberton et al. 2004; Datta CID 755673 et al. 2005; Chang and Nie 2007; French et al. 2008; Takano et al. 2008) and asthma (Kuperman et al. 2005). On the basis of these observations it is proposed that intelectin plays a role in host defense against invading pathogenic microorganisms. In the present study we found that human intelectin-1 is usually a serum protein that binds to bacillus Calmette-Guérin (BCG). Secreted intelectin-1 appears to deposit on mammalian cell surfaces through an autocrine and/or paracrine mechanism. The deposition of intelectin-1 on epithelial cell lines assists in the capture of BCG. Mouse macrophages phagocytosed BCG more efficiently in the medium made up of mouse intelectin-1 than in the control medium. These results suggest that intelectin is usually a host defense lectin that assists in phagocytic clearance of microorganisms. Results Binding of intelectin-1 to BCG Human intelectin-1 was purified from serum by using galactose-Sepharose. Serum intelectin-1 showed a similar band to recombinant intelectin-1 on Western blotting under nonreducing (Physique ?(Physique1A 1 left panel) and reducing conditions (Physique ?(Physique1A 1 right panel). Recombinant human intelectin-1 is usually a 120-kDa disulfide-linked CID 755673 homotrimer (Tsuji et al. 2007). Thus this result indicates that intelectin-1 is present in human serum as a trimer. The concentration of intelectin-1 in human plasma was measured by an enzyme-linked immunosorbent assay (ELISA) and was found to be 95.5 CID 755673 ± 41.4 ng/mL (mean ± SD) in a cohort of normal healthy adult donors (= 17 40.8 ± 7.2 years old). Fig. 1 Binding of human serum intelectin-1 to BCG. Recombinant human intelectin-1 (by saccharides (Tsuji et al. 2001). Thus intelectin-1 likely binds to arabinogalactan on BCG as well. Fig. 2 Flow cytometric analysis of intelectin-1-binding to BCG. HK-BCG was incubated in culture supernatant of human intelectin-1-transfected RK-13 cells with (thin line in A) or without (strong line in A) 10 mM EDTA or with 100 mM saccharide (B). The bacteria … Structure of human intelectin-1 required for hN-CoR binding to BCG To investigate whether the trimeric structure of human intelectin-1 is required to bind BCG we precipitated point-mutated intelectin-1 with HK-BCG from culture supernatants made up of monomeric dimeric or trimeric intelectin-1. Monomeric intelectin-1 bound to galactose-Sepharose but not to HK-BCG (Physique ?(Physique3 3 lanes 1 and 4). Dimeric intelectin-1 and trimeric native intelectin-1 bound to both galactose-Sepharose and HK-BCG; however more intelectin-1 bound to galactose-Sepharose than to HK-BCG (Physique ?(Physique3 3 lanes 2 3 5 and 6). These results suggest that an oligomerized structure is required for human intelectin-1 for binding to HK-BCG unlike binding to galactose-Sepharose. Fig. 3 The requirement of the oligomeric structure of human intelectin-1 for binding to BCG. As explained in … To investigate whether another mammalian CID 755673 intelectin binds to BCG mouse intelectin-1 was tested. Although mouse intelectin-1 is usually monomeric (Tsuji et al. 2007) mouse intelectin-1 bound to both HK-BCG and galactose-Sepharose in a similar proportion (Physique ?(Physique4 4 lanes 4 and 8). Thus mouse intelectin-1 does not require an oligomerized structure for the binding to HK-BCG. Fig. 4 The binding of mouse intelectin-1 to BCG. Recombinant human.