Activation of human monocytes by streptococcal rhamnose glucose polymers is mediated by CD14 antigen, and mannan binding protein inhibits TNF-alpha release.

Abstract

The present work was initiated to define mechanisms that account for the binding on human monocytes of streptococcal cell wall polysaccharides formed by rhamnose glucose polymers (RGPs), and subsequent stimulatory activities. We show here that RGPs bind to and stimulate human monocytes to produce TNF-alpha in a dose-dependent manner. To detect cell surface RGPs binding proteins, intact monocytes were biotinylated before lysis with Nonidet P-40 and solubilized proteins were incubated with RGPs Affi-Prep beads. One major membrane protein of 55 kDa was specifically detected and identified as CD14 because it reacted with anti-CD14 mAbs. Furthermore, anti-CD14 mAbs were able to perform a dose-dependent inhibition of RGPs binding, and suppressed TNF-alpha release from RGPs-stimulated monocytes. Moreover, we demonstrated that RGPs also bind to CD11b; however, this binding is not implicated in synthesis of TNF-alpha. Interestingly, RGPs binding to monocytes was enhanced by human normal serum (HNS) whereas HNS inhibits the TNF-alpha-stimulating activity of RGPs. Western blotting analysis of HNS proteins purified on RGPs Affi-prep beads revealed three specific bands of 75, 55, and 32 kDa reactive with anti-C3 Abs, anti-CD14 mAbs (TUK4), and anti-human mannan binding protein (hMBP)-derived peptide IgG, respectively. These results suggest that C3, soluble CD14, and hMBP form complexes that are probably active in enhancing the binding of RGPs to monocytes. Additional studies have shown that hMBP that recognizes RGPs prevents, unlike the LPS binding protein, TNF-alpha release by inhibiting the binding of RGPs to CD14 Ag. By incubating cells with a constant amount of RGPs-hMBP complexes in the presence or absence of increasing concentrations of C1q, we also demonstrated that C1q receptor mediates the binding and probably the uptake of RGPs-hMBP complexes by human monocytes.

Anais Do Iii Congresso Nacional De Residências Em Saúde (On-Line) – Resumos Expandidos

“…A literatura reporta que a MBL é capaz de ativar a cascata do complemento e induzir a fagocitose, como também impedir a liberação de fator de necrose tumoral alfa (TNF-α). Portanto, com o défice de MBL é propiciado uma resposta inflamatória sustentada e prolongada no período gravídico, beneficiando a atuação do TNF-α, bem como de outras citocinas pró-inflamatórias, tais como as interleucinas IL-12, IL-8, IL-6 e IL-1β, nas quais atuam nas vias moleculares de resistência à insulina (SOELL et al, 1995;MEGIA et al, 2004;KAWAI e AKIRA, 2010).…”

Oral streptococci: modulators of health and disease

“…The RGP’s contribution to adhesion was also demonstrated for THP-1, dental pulp and periodontal ligament cells, which upregulated the production of IL-6 and IL-8 in response to bacterial challenge dependent on the presence of RGP as well as AgI/II on the cell surface ( Engels-Deutsch et al., 2003 ). RGP binds to human monocytes in a CD14-dependent manner and induces the release of TNF-α and other pro-inflammatory cytokines ( Benabdelmoumene et al., 1991 ; Soell et al., 1995 ) as well as the up-regulation of RFc γ ( Benabdelmoumene et al., 1991 ). RGP derived from S. mutans OMZ175 binds epithelial as well as endothelial cells in a dose-dependent manner and stimulates the release of IL-8 and IL-6 ( Vernier et al., 1996 ).…”