Light chain contribution to specificity in anti-DNA antibodies.

Abstract

We studied mice expressing one of two H chain transgenes. Both transgenes expressed the same 3H9 anti-DNA VDJ, but differed in their constant domains. The IgM transgene efficiently induced tolerance and selected for a subset of endogenous L chains that prevented dsDNA binding. In contrast, the IgG2b secreted-only H chain allowed expression of a broad range of L chains, most of which yielded anti-dsDNA Ab. To deduce the features of L chains that affect DNA binding, we derived hybridomas from LPS-stimulated splenic B cells from the two transgene lines and compared the V kappa sequences of Ab they secreted. Identification of L chains with related sequences but different binding to ssDNA, dsDNA, and cardiolipin allowed us to pinpoint L chain residues that correlate with enhanced or reduced binding. Arginines at the junction of V kappa 1 or V kappa 8 regions and J kappa 1, and arginines or asparagines in CDR1 or CDR2 enhanced DNA binding. Negatively charged residues at the same positions were found to interfere with binding. Thus, we predict that appropriate amino acids at these positions may form contacts with DNA. The likely locations of contact residues in the combining site were evaluated by inspection of previously determined Ab structures. Our results indicate that L chains in anti-DNA Ab are able to modulate DNA binding and contribute contact sites for additional determinants on a complex autoantigen.

Age-associated B cells are heterogeneous and dynamic drivers of autoimmunity in mice

“…We therefore asked whether an anti-DNA BCR would enhance ABC formation in an autoimmune context, and if so, whether TLR9 is necessary for this, using MRL/lpr mice expressing the 3H9 BCR heavy chain as a transgene ( Nickerson et al, 2013 ). In these animals, pairing of the heavy chain with most endogenous light chains results in anti-nucleosome or anti-dsDNA reactivity ( Ibrahim et al, 1995 ). The proportion of CD11c + CD11b + and CD11c + B cells, but not CD11b + single-positive cells, was greater in 3H9 + mice than in nontransgenic controls ( Fig.…”

Structural basis for autoantibody recognition of phosphatidylserine-[beta]2-glycoprotein I and apoptotic cells

“…Thus, it is possible that immature B cells expressing VH3H9 participate in the removal of apoptotic cell remnants. However, we know that VH3H9 plays a dominant role in the binding to DNA and phospholipids (37)(38)(39), that most VL cannot block this binding (38), and that editing of VH and͞or VL genes becomes obligatory. This principle is demonstrated by the fact that recombinase-deficient preB cells expressing the 3H9 VH and VL transgenes die by apoptosis (16).…”