mannan-binding-lectin

Examples of mannan-binding-lectin in the following topics:

• Role of the Complement System in Immunity

  • The antibody binds to an antigen on the surface of a pathogen, activating the C1 complement protein.
  • The lectin pathway is not caused by antibody binding, but by a carbohydrate-binding-protein called mannan-binding-lectin (MBL).
  • It is an acute phase reactant produced in the liver and binds to the carbohydrates on the surfaces of many pathogens.
  • The steps for the lectin pathway are:

• The Complement System

  • Three biochemical pathways activate the complement system: the classical complement pathway, the alternative complement pathway, and the lectin pathway.
  • The classical complement pathway typically requires antigen, antibody complexes for activation (specific immune response), whereas the alternative and mannose-binding lectin pathways can be activated by C3 hydrolysis or antigens without the presence of antibodies (non-specific immune response).
  • Such immunoglobulin-mediated binding of the complement may be interpreted, as that the complement uses the ability of the immunoglobulin to detect and bind to non-self antigens as its guiding stick.
  • Some components have a variety of binding sites.
  • C3b binds to antigen-associated Ig and to the microbe surface.

• The Complement System

  • The complement system can be activated through three major pathways: classical, lectin, and alternative.
  • Initiation of the classical pathway occurs when C1q, in complex with C1r and C1s serine proteases (the C1 complex), binds to the Fc region of complement-fixing antibodies (generally IgG1and IgM) attached to pathogenic surfaces.
  • When C3 is cleaved into C3b, it exposes an internal thioester bond that allows stable covalent binding of C3b to hydroxyl groups on proximate carbohydrates and proteins.

• Pili and Pilus Assembly

  • Some fimbriae can contain lectins.
  • The lectins are necessary to adhere to target cells, because they can recognize oligosaccharide units on the surface of these target cells.
  • Other fimbriae bind to components of the extracellular matrix.

• Coryza and Influenza

  • HA is a lectin that mediates binding of the virus to target cells and entry of the viral genome into the target cell, while NA is involved in the release of progeny virus from infected cells, by cleaving sugars that bind the mature viral particles.