title: Commercially available complement component-depleted sera are unexpectedly codepleted of ficolin-2.
abstract: The ficolins are a family of innate pattern recognition molecules that are known to bind acetylated compounds and activate complement through the association of mannose binding lectin (MBL)/ficolin-associated serine proteases (MASPs). Their importance has more recently become appreciated, as they have been shown to play a role in a variety of disease processes from infection to autoimmunity. While studying ficolin-2-mediated complement deposition on Streptococcus pneumoniae, we found that sera depleted of C1q or other complement components were also codepleted of ficolin-2 but not ficolin-1, ficolin-3, or MBL. MBL present in C1q-depleted sera was able to mediate complement deposition on Saccharomyces cerevisiae, suggesting the presence of MASPs. We found that complement was activated on pneumococci in C1q-depleted serum only after opsonization with exogenous recombinant ficolin-2 (rFicolin-2). Also, no complement deposition was observed in C1q-depleted serum when pneumococci were opsonized with rFicolin-2 mutated at its lysine-57 residue, where MASPs are known to associate. Thus, these depleted sera are a unique tool to study ficolin-2-mediated complement pathways; however, one should be aware that ficolin-2 is absent from complement component-depleted sera.
authors.affiliation: Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama, USA.
authors.forename: Allison M
authors.initials: AM
authors.lastname: Brady
authors.affiliation: Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama, USA.
authors.forename: K Aaron
authors.initials: KA
authors.lastname: Geno
authors.affiliation: Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama, USA.
authors.forename: Alex G
authors.initials: AG
authors.lastname: Dalecki
authors.affiliation: Department of Surgery, University of Alabama at Birmingham, Birmingham, Alabama, USA.
authors.forename: Xiaogang
authors.initials: X
authors.lastname: Cheng
authors.affiliation: Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama, USA nahm@uab.edu.
authors.forename: Moon H
authors.initials: MH
authors.lastname: Nahm
mesh_terms: D000328:Adult; D015922:Complement C1q / Q000276:immunology*; D006801:Humans; D037102:Lectins / Q000032:analysis* / Q000276:immunology*; D012441:Saccharomyces cerevisiae / Q000276:immunology; D044967:Serum / Q000737:chemistry*; D013296:Streptococcus pneumoniae / Q000276:immunology; D000097604:Ficolins
chemical_list: D015922:Complement C1q; D037102:Lectins; D000097604:Ficolins