Isotype-Switched Autoantibodies Are Necessary To Facilitate Central Nervous System Autoimmune Disease in Aicda−/− and Ung−/− Mice

Abstract

B cell-depleting therapies have been shown to ameliorate symptoms in multiple sclerosis (MS) patients; however, the mechanism of action remains unclear. Following priming with Ag, B cells undergo secondary diversification of their BCR, including BCR class-switch recombination (CSR) and somatic hypermutation (SHM), with both processes requiring the enzyme activation-induced (cytidine) deaminase. We previously reported that activation-induced (cytidine) deaminase is required for full clinical manifestation of disease in an animal model of MS (experimental autoimmune encephalomyelitis; EAE) provoked by immunization with the extracellular domain of recombinant human myelin oligodendrocyte glycoprotein (hMOG). In this study, we investigated the role of CSR versus SHM in the pathogenesis of EAE. We found that passive transfer of class-switched anti-MOG IgG1 Abs into hMOG-primed mice is sufficient to fully rescue EAE disease. In addition, we found that the nature of the Ag is an important determinant of EAE severity in mice because the lack of a diversified BCR does not affect the induction of EAE when immunized with the extracellular domain of rat MOG. To discriminate the effect of either CSR or SHM, we induced EAE in uracil DNA glycosylase-deficient mice () that exhibit a defect primarily in CSR. We observed that mice exhibit milder clinical disease compared with control mice, concomitant with a reduced amount of anti-MOG IgG class-switched Abs that preserved normal affinity. Collectively, these results indicate that CSR plays an important role in governing the incidence and severity of EAE induced with hMOG but not rat MOG.

Siponimod therapy implicates Th17 cells in a preclinical model of subpial cortical injury

“…In addition, anti-MOG IgG titers were very low or not detected in naive SJL/J mice (as expected) or A/T SJL/J mice ( Figure 3A and Supplemental Figure 3). In terms of anti-MOG IgM responses, in agreement with our previous findings (28), immunization of C57BL/6 mice resulted in very low to undetectable titers of anti-MOG IgM presumably because MOG-specific B cells undergo rapid class switch to IgG. In contrast, hMOG-immunized Aicda -/mice produce anti-MOG IgM antibodies at this time point.…”

“…Examination of PLP staining revealed no evidence of cortical demyelination in the brains of C57BL/6 mice immunized with hMOG. Indeed, brains from hMOG-immunized C57BL/6 mice looked very similar in terms of myelin staining to brains from hMOG-immunized Aicda -/mice, which do not succumb to hMOG-induced EAE (28) (Figure 3, C and D). This demonstrates that the generation of anti-MOG IgG (or IgM) antibodies in response to hMOG immunization is not sufficient to induce demyelination of the cortex of C57BL/6 mice, although there are likely other factors lacking in C57BL/6 hMOG-immunized mice that are present in SJL/J A/T EAE mice.…”

“…EAE induced by immunization with hMOG was used to compare anti-MOG antibody responses with A/T SJL/J EAE. Briefly, C57BL/6 or Aicda −/− littermate control mice were immunized with recombinant hMOG -corresponding to the extracellular domain of human MOG -provided by C. Linington (University of Glasgow, Glasgow, United Kingdom) and N. Ruddle (Yale School of Medicine, New Haven, Connecticut, USA) and prepared as previously described (28). Mice 6-8 weeks of age were immunized subcutaneously with 100 μg of hMOG emulsified 1:1 in incomplete Freund's adjuvant containing 4 mg/ mL Mycobacterium tuberculosis (H37 Ra).…”

“…In such cases, generation of anti-MOG antibodies is either correlated with or required for subpial demyelination (20,21,27). To test whether anti-MOG antibodies are associated with cortical pathology in A/T SJL/J EAE, we measured anti-MOG antibody levels in serum from these mice as well as C57BL/6 mice immunized with human recombinant MOG (hMOG) protein as a technical positive control because hMOG-immunized C57BL/6 mice generate anti-MOG IgG antibodies that are required for the manifestation of clinical disease (28). As a negative control, we examined anti-MOG antibody levels in hMOG-immunized Aicda -/mice, which can only generate an anti-MOG IgM response and consequently show limited evidence of clinical disease (29,30).…”

HDACi mediate UNG2 depletion, dysregulated genomic uracil and altered expression of oncoproteins and tumor suppressors in B- and T-cell lines

“…The quantitative contribution of AID-versus UNG depletion to the HDACi-mediated CSR inhibition could not be determined from our experiments. Nevertheless, a large body of evidence, including work from our own laboratory, has demonstrated the critical function of UNG in CSR [34,[55][56][57], including formation of class switched autoantibodies mediating autoimmune disease [58].…”