Reversing Tolerance in Isotype Switch–Competent Anti-Insulin B Lymphocytes

Abstract

B lymphocytes that escape central tolerance and mature in the periphery are a liability for developing autoimmunity. IgG insulin autoAbs that predict type 1 diabetes and complicate insulin therapies indicate that mechanisms for tolerance to insulin are flawed. To examine peripheral tolerance in anti-insulin B cells, we generated C57BL/6 mice that harbor anti-insulin VDJH-125 site-directed to the native Ig H chain locus (VH125SD). Class switch-competent anti-insulin B cells fail to produce IgG Abs following T cell-dependent (TD) immunization of VH125SD mice with heterologous insulin, and they exhibit markedly impaired proliferation to anti-CD40 plus insulin in vitro. In contrast, co-stimulation with LPS plus insulin drives robust anti-insulin B cell proliferation. Further, VH125SD mice produce both IgM and IgG2a anti-insulin Abs following immunization with a conjugate of insulin to type 1 T cell-independent Brucella abortus ring test Ag (BRT). Anti-insulin B cells undergo clonal expansion in vivo and emerge as IgM+ and IgM− GL7+ Fas+ germinal center (GC) B cells following immunization with insulin-BRT, but not BRT alone. Analysis of Igκ genes in VH125SD mice immunized with insulin-BRT reveals that anti-insulin Vκ from the pre-immune repertoire are selected into GCs. These data demonstrate that class switch-competent anti-insulin B cells remain functionally silent in TD immune responses, yet these B cells are vulnerable to reversal of anergy following combined BCR/TLR engagement that promotes Ag-specific GC responses and Ab production. Environmental factors that lead to infection and inflammation could play a critical yet under-appreciated role in driving loss of tolerance and promoting autoimmune disease.

Molecular regulation of peripheral B cells and their progeny in immunity

“…The Ca ++ /NFAT pathway is also active in B cells rendered tolerant to a low-affinity natural self-antigen (insulin) but, in this case, without uncoupling of NF-κB signaling (Acevedo-Suarez et al 2006). The resulting imbalance in different NFATs maintains tolerance in nonautoimmune B6 mice (Bonami et al 2014;Williams et al 2015). However, in genetically autoimmune mice, these B cells are recruited into GCs and produce autoantibody (Wan et al 2016).…”

Anti-Insulin B Cells Are Poised for Antigen Presentation in Type 1 Diabetes

“…Further, in the absence of class switch recombination, it is impossible to assess the production of IgG autoantibodies, which are currently the most accurate predictors of T1D development in genetically susceptible individuals (18)(19)(20). To address how a fully functional, anti-insulin VH gene impacts disease, we targeted VDJH125 to the IgH chain locus in embryonic stem cells and used them to produce C57BL/6 (B6) and NOD mice harboring an anti-insulin VH (V H 125 SD ) (21,22).…”

“…In non-autoimmune-prone B6 mice, these autoreactive B cells do not generate insulin autoantibodies spontaneously or in response to T-dependent immunization with heterologous insulin, and they have impaired proliferation to anti-CD40 and insulin in vitro. However, tolerance can be reversed following combined BCR/TLR stimulation, which results in Ag-specific germinal center responses and Ab production (21). Whether tolerance is similarly maintained in an autoimmune environment, however, is unknown.…”

Immunological tolerance as a barrier to protective HIV humoral immunity

“…Studies in the autoreactive Ig models of B cell anergy have shown that anergic B cells can mount an antibody response under various conditions, such as stimulation with highly multimerized antigens and/or strong toll-like receptor stimulation [55–57]. As such, a strategy designed to activate the peripheral pool of anergic B cells in bnAb Ig knockin mice would be expected to provide insight for vaccination approaches.…”