title: Blood collection tubes influence serum ficolin-1 and ficolin-2 levels.
abstract: The ficolins are members of a recently discovered family of host innate opsonins that can activate the lectin pathway of complement. The ficolins bind many ligands, although they are typically described as binding acetylated sugars. Ficolin-1 (M-ficolin) and ficolin-2 (L-ficolin) are known to bind Streptococcus pneumoniae serotypes 19C and 11A, respectively. While studying the binding of ficolins to pneumococci, we found variations in ficolin-2 binding among serum samples collected in different types of blood collection tubes. Plastic tubes, which contain a silica clot activator, yielded sera with reduced ficolin-2 binding and apparent ficolin-2 levels. We found that the silica clot activator eluted from plastic red-top tubes inhibited ficolin-2 ligand binding, while other related proteins, like mannose-binding lectin (MBL) and ficolin-1, were not affected. These tube types did not affect the concentrations of other related opsonins (C1q, MBL, or ficolin-3 [H-ficolin]). Interestingly, we also found that ficolin-1 levels were increased 2- to 3-fold in plastic serum separator tubes compared to the increases in other tube types. These findings have implications for future ficolin-1 and ficolin-2 studies, as proper sample collection and handling are essential.
authors.affiliation: Department of Pathology, University of Alabama at Birmingham, Birmingham, Alabama, USA.
authors.forename: Allison M
authors.initials: AM
authors.lastname: Brady
authors.forename: Brady L
authors.initials: BL
authors.lastname: Spencer
authors.forename: Ann R
authors.initials: AR
authors.lastname: Falsey
authors.forename: Moon H
authors.initials: MH
authors.lastname: Nahm
mesh_terms: D000328:Adult; D003951:Diagnostic Errors; D064368:Healthy Volunteers; D006801:Humans; D037102:Lectins / Q000097:blood*; D044967:Serum / Q000737:chemistry*; D013048:Specimen Handling / Q000379:methods*; D000097604:Ficolins
chemical_list: D037102:Lectins; D000097604:Ficolins