Distinct and synergistic roles of Fc?RIIB deficiency and 129 strain-derived SLAM family proteins in the development of spontaneous germinal centers and autoimmunity.

ABSTRACT: The inhibitory IgG Fc receptor (Fc?RIIB) deficiency and 129 strain-derived signaling lymphocyte activation molecules (129-SLAMs) are proposed to contribute to the lupus phenotype in Fc?RIIB-deficient mice generated using 129 ES cells and backcrossed to C57BL/6 mice (B6.129.RIIBKO). In this study, we examine the individual contributions and the cellular mechanisms by which Fc?RIIB deficiency and 129-derived SLAM family genes promote dysregulated spontaneous germinal center (Spt-GC) B cell and follicular helper T cell (Tfh) responses in B6.129.RIIBKO mice. We find that B6 mice congenic for the 129-derived SLAM locus (B6.129-SLAM) and B6 mice deficient in Fc?RIIB (B6.RIIBKO) have increased Spt-GC B cell responses compared to B6 controls but significantly lower than B6.129.RIIBKO mice. These data indicate that both Fc?RIIB deficiency and 129-SLAMs contribute to elevated Spt-GC B cell responses in B6.129.RIIBKO mice. However, only 129-SLAMs contribute significantly to augmented Tfh responses in B6.129.RIIBKO mice, and do so by a combination of T cell-dependent effects and enhanced B cell and DC-dependent antigen presentation to T cells. Elevated Spt-GC B cell responses in mice with Fc?RIIB deficiency and polymorphic 129-SLAMs were associated with elevated metabolic activity, improved GC B cell survival and increased differentiation of naïve B cells into GC B cell phenotype. Our data suggest that the interplay between 129-SLAM expression on B cells, T cells and DCs is central to the alteration of the GC tolerance checkpoint, and that deficiency of Fc?RIIB on B cells is necessary to augment Spt-GC responses, pathogenic autoantibodies, and lupus disease.

SUBMITTER: Soni C 

PROVIDER: S-EPMC4564365 | biostudies-other | 2015 Sep

REPOSITORIES: biostudies-other