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Jens Christian Jensenius

Cooperation between MASP-1 and MASP-2 in the generation of C3 convertase through the MBL pathway

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The complement system is an important part of the innate immune system. Three pathways, the classical, the alternative and the lectin pathway, lead to the cleavage of complement factor C3, a central event in the activation of the complement system. We investigated the deposition of C3b (solid-phase C3 activation product) on a mannan-coated surface at high concentration of human serum (17%). At these conditions, mannan-binding lectin (MBL) promoted the activation of C3 through the combined action of MBL-associated serine protease (MASP)-1 and MASP-2 without appreciable involvement of the alternative pathway. In serum depleted of MASP-1, MASP-2 and MASP-3, we observed synergetic effect of reconstitution with MASP-1 and MASP-2. This was inhibited by MASP-3. No C3b deposition was observed with C2- or C4-depleted serum. Depletion of factor B had no effect on the MBL-MASP-promoted C3b deposition. Our results demonstrate a function of the orphan protease MASP-1 by providing evidence that this enzyme collaborates with MASP-2 in the generation of C3 convertase, a process observable at high serum concentration, but not at low serum concentration.
Original languageEnglish
JournalInternational Immunology
Volume19
Issue2
Pages (from-to)141-9
Number of pages9
ISSN0953-8178
DOIs
Publication statusPublished - 2007

    Research areas

  • Animals, Complement Activation, Complement C3-C5 Convertases, Complement C3b, Humans, Mannose-Binding Lectin, Mannose-Binding Lectins, Mannose-Binding Protein-Associated Serine Proteases, Mice, Mice, Knockout

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