C1q-binding immunoglobulin G in MRL/l mice consists of immune complexes containing antibodies to DNA.
Previous studies have shown that the majority of C1q-binding IgG in patients with systemic lupus erythematosus (SLE) is composed of autoantibodies to the collagen-like region of C1q. Mice of the MRL/l strain are considered as a murine model of human SLE and possess autoantibodies to nuclear antigens as well as IgM and IgG rheumatoid factors (RF). This study was undertaken to characterize the C1q-binding IgG in MRL/l mice. In contrast to human SLE, C1q-binding IgG in MRL/l mice showed immunochemical characteristics of immune complexes rather than those of autoantibodies to C1q. Namely, C1q-binding IgG in MRL/l mice was large-sized upon HPLC gel filtration and abolished by digestion with pepsin or by high salt concentration, and bound to the globular region of C1q. The C1q-binding activity in MRL/l mice was absorbed by double-stranded DNA- or single-stranded DNA-cellulose. The medium-sized immune complexes containing RF have been well documented in MRL/l mice. In this study, however, mouse IgG-Sepharose failed to absorb fully C1q-binding IgG. We conclude that the majority of C1q-binding IgG in MRL/l mice consists of large-sized immune complexes containing antibodies to DNA.
Uwatoko
S
S
First Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
Mannik
M
M
Oppliger
I R
IR
Okawa-Takatsuji
M
M
Aotsuka
S
S
Yokohari
R
R
Seki
G
G
Taniguchi
S
S
Suzuki
K
K
Kurokawa
K
K
D000818:Animals; D000974:Antibodies, Antinuclear / Q000032:analysis*; D000936:Antigen-Antibody Complex / Q000276:immunology*; D002482:Cellulose; D015922:Complement C1q / Q000378:metabolism*; D004247:DNA / Q000276:immunology; D004277:DNA, Single-Stranded; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism*; D007163:Immunosorbent Techniques; D008181:Lupus Nephritis / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008817:Mice, Mutant Strains; D011485:Protein Binding; D012685:Sepharose
D000974:Antibodies, Antinuclear; D000936:Antigen-Antibody Complex; D004277:DNA, Single-Stranded; D007074:Immunoglobulin G; D015922:Complement C1q; D002482:Cellulose; D004247:DNA; D012685:Sepharose