TY - JOUR

T1 - Circulating Ficolin-2 and Ficolin-3 Form Heterocomplexes

AU - Jarlhelt, Ida

AU - Pilely, Katrine

AU - Clausen, Jytte Bryde

AU - Skjoedt, Mikkel-Ole

AU - Bayarri-Olmos, Rafael

AU - Garred, Peter

N1 - Copyright © 2020 by The American Association of Immunologists, Inc.

PY - 2020

Y1 - 2020

N2 - The complement system constitutes an important part of the innate immune system. The collectins and the ficolins are soluble pattern recognition molecules that contribute to complement activation via the lectin pathway. During previous experiments with ficolin-2 and ficolin-3, we have observed that the molecules may interact. We therefore hypothesized the existence of stable ficolin-2/-3 heterocomplexes. We could demonstrate ficolin-2/-3 heterocomplexes in normal human serum and plasma by ELISA using Abs specific for ficolin-2 and ficolin-3. The formation of heteromeric protein complexes were validated by coimmunoprecipitation and Western blot analysis. When recombinant ficolin-2 and recombinant ficolin-3 were mixed, no complexes were formed. However, when coexpressing ficolin-2 and ficolin-3 in Chinese hamster ovary cells, we could detect ficolin-2/-3 heterocomplexes in the supernatant. Furthermore, we measured concentration of the ficolin-2/-3 heterocomplexes in arbitrary units in 94 healthy individuals. We also established the relationship between the concentrations of ficolin-2, ficolin-3, and the ficolin-2/-3 heterocomplexes. We observed that the concentration of the ficolin-2/-3 heterocomplex correlated significantly with ficolin-2 (ρ: 0.24, p < 0.018) and ficolin-3 concentrations (ρ: 0.46, p < 0.0001). In conclusion, we describe a novel protein complex between ficolin-2 and ficolin-3 present in serum and plasma, which might be of additional biological relevance apart from the native ficolin-2 and ficolin-3 molecules.

AB - The complement system constitutes an important part of the innate immune system. The collectins and the ficolins are soluble pattern recognition molecules that contribute to complement activation via the lectin pathway. During previous experiments with ficolin-2 and ficolin-3, we have observed that the molecules may interact. We therefore hypothesized the existence of stable ficolin-2/-3 heterocomplexes. We could demonstrate ficolin-2/-3 heterocomplexes in normal human serum and plasma by ELISA using Abs specific for ficolin-2 and ficolin-3. The formation of heteromeric protein complexes were validated by coimmunoprecipitation and Western blot analysis. When recombinant ficolin-2 and recombinant ficolin-3 were mixed, no complexes were formed. However, when coexpressing ficolin-2 and ficolin-3 in Chinese hamster ovary cells, we could detect ficolin-2/-3 heterocomplexes in the supernatant. Furthermore, we measured concentration of the ficolin-2/-3 heterocomplexes in arbitrary units in 94 healthy individuals. We also established the relationship between the concentrations of ficolin-2, ficolin-3, and the ficolin-2/-3 heterocomplexes. We observed that the concentration of the ficolin-2/-3 heterocomplex correlated significantly with ficolin-2 (ρ: 0.24, p < 0.018) and ficolin-3 concentrations (ρ: 0.46, p < 0.0001). In conclusion, we describe a novel protein complex between ficolin-2 and ficolin-3 present in serum and plasma, which might be of additional biological relevance apart from the native ficolin-2 and ficolin-3 molecules.

KW - Animals

KW - CHO Cells

KW - Cell Line

KW - Collectins/metabolism

KW - Complement Activation/physiology

KW - Complement Pathway, Mannose-Binding Lectin/physiology

KW - Complement System Proteins/metabolism

KW - Cricetulus

KW - Humans

KW - Lectins/blood

KW - Mannose-Binding Protein-Associated Serine Proteases/metabolism

KW - Mice

U2 - 10.4049/jimmunol.1900694

DO - 10.4049/jimmunol.1900694

M3 - Journal article

C2 - 32094208

VL - 204

SP - 1919

EP - 1928

JO - Journal of Immunology

JF - Journal of Immunology

SN - 0022-1767

IS - 7

ER -