Somatic hypermutation as a generator of antinuclear antibodies in a murine model of systemic autoimmunity

Abstract

Systemic lupus erythematosus (SLE) is characterized by high-avidity IgG antinuclear antibodies (ANAs) that are almost certainly products of T cell–dependent immune responses. Whether critical amino acids in the third complementarity-determining region (CDR3) of the ANA originate from V(D)J recombination or somatic hypermutation (SHM) is not known. We studied a mouse model of SLE in which all somatic mutations within ANA V regions, including those in CDR3, could be unequivocally identified. Mutation reversion analyses revealed that ANA arose predominantly from nonautoreactive B cells that diversified immunoglobulin genes via SHM. The resolution afforded by this model allowed us to demonstrate that one ANA clone was generated by SHM after a VH gene replacement event. Mutations producing arginine substitutions were frequent and arose largely (66%) from base changes in just two codons: AGC and AGT. These codons are abundant in the repertoires of mouse and human V genes. Our findings reveal the predominant role of SHM in the development of ANA and underscore the importance of self-tolerance checkpoints at the postmutational stage of B cell differentiation.

TGF-β prevents T follicular helper cell accumulation and B cell autoreactivity

“…New B cell receptor specificities, including those with autoreactivity, arise continuously during the GC reaction (45)(46)(47). Aberrant accumulation of Tfh cells has been associated with positive selection of self-reactive GC B cells and autoimmunity in both mice and humans (30,48).…”

γδ T cells affect IL-4 production and B-cell tolerance

“…Sera were tested for autoreactivity against fixed HEp-2 human carcinoma cells (Bio-Rad Laboratories) as previously described (24). Briefly, slides with attached HEp-2 cells were incubated with diluted serum samples for 30 min at room temperature, washed with PBS for 5 min, and incubated with FITC-labeled rat anti-mouse Ig κ antibody (1:1,000, clone 187.…”

mTOR has distinct functions in generating versus sustaining humoral immunity

“…Many long-lived plasma cells arise from GCs (6); however, long-lived GC-independent IgM-secreting plasma cells have also been described (7)(8)(9)(10). GC-derived plasma cells may play an especially critical role in humoral autoimmunity, as autoantibodies in mice and in people often possess extensive evidence of somatic hypermutation (SHM) (11)(12)(13)(14)(15). However, despite the essential role played by long-lived plasma cells in immunity and autoimmunity, little is known about the biochemical regulation of early or late phases of plasma cell differentiation and function.…”