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Binding of mouse mannan-binding lectins to different bacterial pathogens of mice

Phaneuf, L.R., Lillie, B.N., Hayes, M.A., Turner, P.V.
Veterinary immunology and immunopathology 2006 v.118 no.1-2 pp. 129-133
mice, immune system, lectins, mannans, binding properties, animal pathogens, bacterial infections, disease resistance, immunity, blood plasma, protein composition, protein structure, amino acid sequences, binding capacity, carbohydrate binding, Escherichia coli, Klebsiella oxytoca, Staphylococcus aureus, Pseudomonas aeruginosa
Humans have one mannan-binding lectin (MBL) in circulation but rodents, pigs, rabbits and rhesus monkeys have two, MBL-A and MBL-C. Plasma forms of these proteins have similar mannan-binding activity in vitro, but might differ in their ability to bind other microbial targets. In these studies, we compared carbohydrate-dependent binding of mouse plasma MBL-A and MBL-C to mannan-sepharose beads and to intact bacteria isolated as pathogens from mice. After incubation of mouse plasma with intact bacteria, MBL-A and MBL-C were eluted with N-acetylglucosamine (GlcNAc) and identified in nonreducing SDS-PAGE using Western blot analysis and MBL-A or MBL-C specific monoclonal antibodies. GlcNAc eluates of plasma incubated with mannan-sepharose beads, Klebsiella oxytoca and Staphylococcus aureus contained similar bands (mainly 50 kDa) that were immunoreactive with MBL-C antibody. Furthermore, a smaller form of MBL-C (45 kDa) was detected bound to Pseudomonas aeruginosa. By comparison, immunoreactive MBL-A (a ladder of 175 kDa and larger bands) was identified in these GlcNAc eluates from mannan-sepharose beads, S. aureus and K. oxytoca but not P. aeruginosa. These studies demonstrate that mouse MBL-A and MBL-C in plasma are not equivalent in their ability to recognize bacteria that are pathogens for mice.