B Cell Activation and Escape of Tolerance Checkpoints:Recent Insights from Studying Autoreactive B Cells

Autoreactive B cells are key drivers of pathogenic processes in autoimmune diseases by the production of autoantibodies, secretion of cytokines, and presentation of autoantigens to T cells. However, the mechanisms that underlie the development of autoreactive B cells are not well understood. Here, we review recent studies leveraging novel techniques to identify and characterize (auto)antigen-specific B cells. The insights gained from such studies pertaining to the mechanisms involved in the escape of tolerance checkpoints and the activation of autoreactive B cells are discussed. In addition, we briefly highlight potential therapeutic strategies to target and eliminate autoreactive B cells in autoimmune diseases

Regulatory and effector B cell cytokine production in patients with relapsing granulomatosis with polyangiitis

Background: B cells are capable of producing regulatory and effector cytokines. In patients with granulomatosis with polyangiitis (GPA), skewing of the pro- and anti-inflammatory cytokine balance may affect the risk of relapse. This study aimed to investigate differences in B cell cytokine production in patients with relapsing GPA and in controls, and determine whether this can aid in relapse prediction. Methods: Thirteen GPA patients with an upcoming relapse were matched with non-relapsing patients and healthy controls in a retrospective design. The B cell subset distribution was determined from peripheral blood. Cryopreserved peripheral blood mononuclear cells were cultured and intracellular B cell production of regulatory (IL10) and effector (TNF alpha, IFN gamma IL2, IL6) cytokines was assessed. Finally, serum markers associated with B cell activation (sCD27) and migration (CCL19) were determined. Results: GPA patient samples exhibited significantly lower percentages of TNF alpha+B cells than controls, an effect that was most pronounced in patients about to relapse. B cell capacity for IL10 production was similar in patients and controls. No significant differences were observed for cytokine production in relapsing and non-relapsing GPA patients. TNFa production correlated strongly with IL2, IFN gamma and the percentage of memory B cells. No change in effector cytokines occurred before relapse, while the percentage of IL10+B cells significantly decreased. GPA patients in remission had increased serum levels of CCL19 and sCD27, and sCD27 levels increased upon active disease. Conclusions: While differences in effector B cell cytokine production were observed between patients and controls, monitoring this in GPA did not clearly distinguish patients about to relapse. Prospective measurements of the regulatory cytokine IL10 may have potential for relapse prediction. Memory B cells appear mainly responsible for effector cytokine production. Increased migration of these cells could explain the decreased presence of TNF alpha+B cells in the circulation

Mycophenolic acid and 6-mercaptopurine both inhibit B-cell proliferation in granulomatosis with polyangiitis patients, whereas only mycophenolic acid inhibits B-cell IL-6 production

Granulomatosis with polyangiitis (GPA) is an autoimmune disease affecting mainly small blood vessels. B-cells are important in the GPA pathogenesis as precursors of autoantibody-producing cells but likely also contribute (auto)antibody-independently. This has been underlined by the effectiveness of B-cell-depletion (with Rituximab) in inducing and maintaining disease remission. Mycophenolate-mofetil (MMF) and azathioprine (AZA) are immunosuppressive therapies frequently used in GPA-patients. Interestingly, MMF-treated GPA-patients are more prone to relapses than AZA-treated patients, while little is known about the influence of these drugs on B-cells. We investigated whether MMF or AZA treatment (or their active compounds) alters the circulating B-cell subset distribution and has differential effects on in vitro B-cell proliferation and cytokine production in GPA-patients that might underlie the different relapse rate. Circulating B-cell subset frequencies were determined in samples from AZA-treated (n = 13), MMF-treated (n = 12), untreated GPA-patients (n = 19) and matched HCs (n = 41). To determine the ex vivo effects of the active compounds of MMF and AZA, MPA and 6-MP respectively, on B-cell proliferation and cytokine production, PBMCs of untreated GPA-patients (n = 29) and matched HCs (n = 30) were cultured for 3-days in the presence of CpG-oligodeoxynucleotides (CpG) with MPA or 6-MP. After restimulation (with phorbol myristate acetate, calcium-ionophore), cytokine-positive B-cell frequencies were measured. Finally, to assess the effect of MMF or AZA treatment on in vitro B-cell proliferation and cytokine production, PBMCs of MMF-treated (n = 18), and AZA-treated patients (n = 28) and HCs (n = 41) were cultured with CpG. The memory B-cell frequency was increased in AZA- compared to MMF-treated patients, while no other subset was different. The active compounds of MMF and AZA showed in vitro that MPA decreased B-cell proliferation in GPA-patients and HCs. B-cell proliferation in MMF- and AZA-treated patients was not different. Finally, the IL-6+ B-cell frequency was decreased by MPA compared to 6-MP. No differences in IL-10+, IL-6+ or TNFα+ B-cell proportions or proliferation were found in MMF- and AZA-treated patients. Our results indicate that MMF could be superior to AZA in inhibiting B-cell cytokine production in GPA-patients. Future studies should assess the effects of these immunosuppressive drugs on other immune cells to elucidate mechanisms underlying the potential differences in relapse rates

Kv1.3 blockade by ShK186 modulates CD4+ effector memory T-cell activity of patients with Granulomatosis with polyangiitis

OBJECTIVES: Granulomatosis with polyangiitis (GPA) is a chronic relapsing systemic autoimmune vasculitis. Current treatment of GPA is unsatisfactory as it relies on strong immunosuppressive regimens, with either cyclophosphamide or rituximab, that reduce the immunogenicity of several vaccines and are risk factors of severe form of COVID-19. This emphasizes the need to identify new drug target and to develop treatment strategies with less harmful side effects. Since CD4+ effector memory T cells (TEM) play a key role in the pathogenesis of GPA, we aimed in this study to modulate CD4+TEM cell activity via Kv1.3 blockade using the specific peptide inhibiter, ShK-186.METHODS: Peripheral blood of 27 GPA-patients in remission and 16 age- and sex-matched healthy controls (HCs) were pre-incubated in vitro in the presence or absence of ShK-186, followed by stimulation with PMA, calcium ionophore and brefeldin-A. The effect of ShK-186 on the cytokine production (IFNγ, TNFα, IL-4, IL-17, IL-21) within total and subsets of CD4+TH cells were assessed using flow cytometry.RESULTS: ShK-186 reduced the expression level of IFNγ, TNFα, IL-4, IL-17, and IL-21 in CD4+TH cells from GPA-patients in vitro. Further analysis performed on sorted CD4+T cell subsets, revealed that ShK-186 predominantly inhibited the cytokine production of CD4+TEM cells. ShK-186 treatment reduced the production of the pro-inflammatory cytokines to the level seen in CD4+ TH cells from HCs.CONCLUSIONS: Modulation of cellular effector function by ShK-186 may constitute a novel treatment strategy for GPA with high specificity and less harmful side effects.</p

Kv1.3 blockade by ShK186 modulates CD4+ effector memory T-cell activity of patients with Granulomatosis with polyangiitis

OBJECTIVES: Granulomatosis with polyangiitis (GPA) is a chronic relapsing systemic autoimmune vasculitis. Current treatment of GPA is unsatisfactory as it relies on strong immunosuppressive regimens, with either cyclophosphamide or rituximab, that reduce the immunogenicity of several vaccines and are risk factors of severe form of COVID-19. This emphasizes the need to identify new drug target and to develop treatment strategies with less harmful side effects. Since CD4+ effector memory T cells (TEM) play a key role in the pathogenesis of GPA, we aimed in this study to modulate CD4+TEM cell activity via Kv1.3 blockade using the specific peptide inhibiter, ShK-186.METHODS: Peripheral blood of 27 GPA-patients in remission and 16 age- and sex-matched healthy controls (HCs) were pre-incubated in vitro in the presence or absence of ShK-186, followed by stimulation with PMA, calcium ionophore and brefeldin-A. The effect of ShK-186 on the cytokine production (IFNγ, TNFα, IL-4, IL-17, IL-21) within total and subsets of CD4+TH cells were assessed using flow cytometry.RESULTS: ShK-186 reduced the expression level of IFNγ, TNFα, IL-4, IL-17, and IL-21 in CD4+TH cells from GPA-patients in vitro. Further analysis performed on sorted CD4+T cell subsets, revealed that ShK-186 predominantly inhibited the cytokine production of CD4+TEM cells. ShK-186 treatment reduced the production of the pro-inflammatory cytokines to the level seen in CD4+ TH cells from HCs.CONCLUSIONS: Modulation of cellular effector function by ShK-186 may constitute a novel treatment strategy for GPA with high specificity and less harmful side effects.</p

Kv1.3 blockade by ShK186 modulates CD4+ effector memory T-cell activity of patients with Granulomatosis with polyangiitis

OBJECTIVES: Granulomatosis with polyangiitis (GPA) is a chronic relapsing systemic autoimmune vasculitis. Current treatment of GPA is unsatisfactory as it relies on strong immunosuppressive regimens, with either cyclophosphamide or rituximab, that reduce the immunogenicity of several vaccines and are risk factors of severe form of COVID-19. This emphasizes the need to identify new drug target and to develop treatment strategies with less harmful side effects. Since CD4+ effector memory T cells (TEM) play a key role in the pathogenesis of GPA, we aimed in this study to modulate CD4+TEM cell activity via Kv1.3 blockade using the specific peptide inhibiter, ShK-186.METHODS: Peripheral blood of 27 GPA-patients in remission and 16 age- and sex-matched healthy controls (HCs) were pre-incubated in vitro in the presence or absence of ShK-186, followed by stimulation with PMA, calcium ionophore and brefeldin-A. The effect of ShK-186 on the cytokine production (IFNγ, TNFα, IL-4, IL-17, IL-21) within total and subsets of CD4+TH cells were assessed using flow cytometry.RESULTS: ShK-186 reduced the expression level of IFNγ, TNFα, IL-4, IL-17, and IL-21 in CD4+TH cells from GPA-patients in vitro. Further analysis performed on sorted CD4+T cell subsets, revealed that ShK-186 predominantly inhibited the cytokine production of CD4+TEM cells. ShK-186 treatment reduced the production of the pro-inflammatory cytokines to the level seen in CD4+ TH cells from HCs.CONCLUSIONS: Modulation of cellular effector function by ShK-186 may constitute a novel treatment strategy for GPA with high specificity and less harmful side effects.</p

Kv1.3 blockade by ShK186 modulates CD4+ effector memory T-cell activity of patients with Granulomatosis with polyangiitis

OBJECTIVES: Granulomatosis with polyangiitis (GPA) is a chronic relapsing systemic autoimmune vasculitis. Current treatment of GPA is unsatisfactory as it relies on strong immunosuppressive regimens, with either cyclophosphamide or rituximab, that reduce the immunogenicity of several vaccines and are risk factors of severe form of COVID-19. This emphasizes the need to identify new drug target and to develop treatment strategies with less harmful side effects. Since CD4+ effector memory T cells (TEM) play a key role in the pathogenesis of GPA, we aimed in this study to modulate CD4+TEM cell activity via Kv1.3 blockade using the specific peptide inhibiter, ShK-186.METHODS: Peripheral blood of 27 GPA-patients in remission and 16 age- and sex-matched healthy controls (HCs) were pre-incubated in vitro in the presence or absence of ShK-186, followed by stimulation with PMA, calcium ionophore and brefeldin-A. The effect of ShK-186 on the cytokine production (IFNγ, TNFα, IL-4, IL-17, IL-21) within total and subsets of CD4+TH cells were assessed using flow cytometry.RESULTS: ShK-186 reduced the expression level of IFNγ, TNFα, IL-4, IL-17, and IL-21 in CD4+TH cells from GPA-patients in vitro. Further analysis performed on sorted CD4+T cell subsets, revealed that ShK-186 predominantly inhibited the cytokine production of CD4+TEM cells. ShK-186 treatment reduced the production of the pro-inflammatory cytokines to the level seen in CD4+ TH cells from HCs.CONCLUSIONS: Modulation of cellular effector function by ShK-186 may constitute a novel treatment strategy for GPA with high specificity and less harmful side effects.</p