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author:(Liliane J dable)
1.  C1q deficiency promotes the production of transgenic-derived IgM and IgG3 autoantibodies in anti-DNA knock-in transgenic mice 
Molecular Immunology  2008;45(3):787-795.
C1q-deficient mice have been shown to develop a lupus-like disease and to display an impaired clearance of apoptotic cells that are enriched in lupus autoantigens. However, the role of C1q in the regulation of autoreactive B cells remains debatable. To explore this we crossed MRL/Mp C1q-deficient mice with knock-in transgenic (Tg) mice expressing an anti-ssDNA antibody (VH3H9R and VH3H9R/VLκ8R). Analysis of the VH3H9R mice showed that in the absence of C1q higher titres of Tg-derived IgM and IgG3 anti-ssDNA antibodies were detectable. In contrast, in the VH3H9R/VLκ8R C1q-deficient animals no increase in Tg antibody levels was observed. In both models the lack of C1q induced a marked reduction of marginal zone B cells and this was paralleled by a significant increase in the percentage of plasmocytes. Thus, one could postulate that in the absence of C1q the failure to clear efficiently dying cells provides an additional stimulus to the autoreactive Tg B cells resulting in their emigration from the marginal zone B cell compartment with subsequent increase in plasmocytes. However, the lack of C1q led to an increased production of Tg IgM and IgG3 antibodies only in VH3H9R mice indicating that additional genetic susceptibility factors are required to break self-tolerance.
PMCID: PMC2080686  PMID: 17675234
Ab, antibody; AEU, arbitrary ELISA units; FO, follicular; HEL, hen egg lysozyme; MZ, marginal zone; Tg, transgenic; SLE, systematic lupus erythematosus; Autoimmunity; Complement; B cells; Rodent; Transgenic
2.  Complement Activation Selectively Potentiates the Pathogenicity of the IgG2b and IgG3 Isotypes of a High Affinity Anti-Erythrocyte Autoantibody 
By generating four IgG isotype-switch variants of the high affinity 34–3C anti-erythrocyte autoantibody, and comparing them to the IgG variants of the low affinity 4C8 anti-erythrocyte autoantibody that we have previously studied, we evaluated in this study how high affinity binding to erythrocytes influences the pathogenicity of each IgG isotype in relation to the respective contributions of Fcγ receptor (FcγR) and complement. The 34–3C autoantibody opsonizing extensively circulating erythrocytes efficiently activated complement in vivo (IgG2a = IgG2b > IgG3), except for the IgG1 isotype, while the 4C8 IgG autoantibody failed to activate complement. The pathogenicity of the 34–3C autoantibody of IgG2b and IgG3 isotypes was dramatically higher (>200-fold) than that of the corresponding isotypes of the 4C8 antibody. This enhanced activity was highly (IgG2b) or totally (IgG3) dependent on complement. In contrast, erythrocyte-binding affinities only played a minor role in in vivo hemolytic activities of the IgG1 and IgG2a isotypes of 34–3C and 4C8 antibodies, where complement was not or only partially involved, respectively. The remarkably different capacities of four different IgG isotypes of low and high affinity anti-erythrocyte autoantibodies to activate FcγR-bearing effector cells and complement in vivo demonstrate the role of autoantibody affinity maturation and of IgG isotype switching in autoantibody-mediated pathology.
PMCID: PMC2193744  PMID: 11901193
autoimmune hemolytic anemia; complement receptor; Fc receptor; IgG isotype; phagocytosis
3.  Identification and characterisation of a lupus suppressor 129 locus on chromosome 31 
The 129-derived Sle16 is a susceptibility locus for systemic autoimmunity when present on the C57BL/6 (B6) background. Genetic analysis of a (129×B6)F2 cross identified a region from the B6 chromosome 3 (Sle18) with positive linkage to anti-nuclear antibodies. Here we have generated a B6 congenic strain harbouring the 129 allele of Sle18 and intercrossed this line with the lupus-prone B6.129-Sle16 strain. The presence of the 129-Sle18 allele in the B6.129-Sle16Sle18 double congenic mice suppressed the development of Sle16-mediated autoantibody production and ameliorated the renal pathology. The 129-Sle18 locus rectified the B cell abnormalities detected in the B6.129-Sle16 mice, such as the reduction in the percentage of marginal zone B and B1a cells and the increased number of germinal centers. The B6.129-Sle16Sle18 spleens still displayed an increased percentage of activated T and B cells. However, in the B6.129-Sle16Sle18 strain the percentage of naïve T cells was equivalent to that in B6.129-Sle18 and B6 mice and these cells showed a reduced proliferative response to anti-CD3 stimulation compared to B6.129-Sle16 T cells. There was a significant increase in the percentage of CD4+FoxP3+regulatory T cells in all congenic strains. These cells had normal regulatory function when tested in vitro. Thus 129-Sle18 represents a novel, non-MHC lupus-suppressor locus probably operating as a functional modifier of B cells that, in combination with other factors, leads to lupus resistance. Further characterisation of this locus will help to uncover the immune mechanism(s) conferring protection against lupus.
PMCID: PMC3698755  PMID: 20435933
systemic lupus erythematosus; autoantibodies; rodent; congenic

Results 1-3 (3)