Molecular basis of 9G4 B cell autoreactivity in human SLE

9G4+ IgG antibodies expand in SLE in a disease specific fashion and react with different lupus antigens including B cell antigens and apoptotic cells. Their shared use of VH4-34 represents a unique system to understand the molecular basis of lupus autoreactivity. Understanding the participation of apoptotic cells, a rich source of self-antigens including chromatin, in the diversification and selection of autoreactive memory B cells is particularly important in SLE where these cells accumulate in the germinal centers and may activate pathogenic autoreactive B cells. Our findings indicate that the three mabs with strong apoptotic binding recognized chromatin and individual histones as documented by glomerular proteome microarrays. While the actual antigens mediating APCB remain to be formally elucidating, our initial studies indicate that binding to histone/chromatin may mediate such autoreactivity in at least a fraction of these antibodies Single VH4-34 B cells sorted from IgD-CD27+ memory B cells of SLE patient are sorted and single -RT-PCR is performed to generate monoclonal antibody. 3 monoclonals which were strong apoptotic binders tested for protein array against Chromatin, Histone1, Histone 2A, Histone 2B, Histone 3, Histone 4 and total histones