The Role Of Plasmablast In The Development Of Type 1 Diabetes Mellitus

Background and aims:Type 1 diabetes mellitus(T1DM)is a chronic autoimmune disease characterized by the destruction of pancreatic β-cell.Although T cells are the primary pathogenic effectors in T1DM,mounting evidence indicates a crucial role for B cells in disease pathogenesis.However,exactly how B-cell subsets contribute to T1DM remains elusive.This study aimed to identify the diabetogenic B-cell subset and to explore the potential role of the pathogenic B-cell subset in T1DM.Methods:We enrolled 56 people with T1DM,including 36 new-onset patients(disease duration<1 year)and 20 long-term patients(disease duration≥1 year),22 people with type 2 diabetes,and 26 healthy controls.Frequencies and surface markers of B cell subsets were detected by flow-cytometry.Pearson or Spearman correlation analyses were conducted to explore the relationship between B cell subsets and clinical characteristics of patients with T1DM.Cell co-culture and ELISPOT assay were used to assess the role of B-cell subset in activation of diabetogenic T cells.To explore the role of plasmablast in the process of T1DM,frequency of plasmablasts was detected by flow-cytometry in the spleen and pancreatic lymph nodes(PLNs)of nonobese diabetic(NOD)mice with different ages.Infiltration of plasmablasts in the islets was analyzed by immunofluorescence.Meanwhile,plasmablasts and T cells sorted from the spleen and PLNs of 16-week NOD mice were co-cultured with islets of 5-week NOD mice for 72h.TUNEL was used to assess the apoptosis of islets after co-culture.Adoptive transfer assay was utilized to further determine the pathogenic role of plasmabalsts in vivo.Plasmablasts mixed with T cells were sorted from the spleen and PLN of 16-week NOD mice,and were transferred intravenously into 6-week NOD/SCID mice.Diabetes incidence and severity of insulitis were examinedResults:Frequency of B cells was significantly increased in patients with T1DM,while frequencies of CD4+T cells and CD8+T cells were comparable among groups.Plasmablasts,but not naive,unswitched or CD38-/+ switched memory B cells,were significantly increased in patients with new-onset T1DM compared with healthy controls.Frequency of plasmablast increased both in juvenile-onset and adult-onset T1DM patients.Correlation analyses showed that plasmablast number negatively correlated with fasting and post-meal C-peptide in patients with new-onset T1DM.Additionally,plasmablast was increased in patients who were positive for GADA.Plasmablast remain the expression of HLA-Ⅱ.Compared with other B-cell subsets,plasmablasts expressed a high level of CD86,which negatively correlated with the residual β-cell function while positively correlated with the number of islet autoantibodies.ELISPOT assay further showed that plasmablasts isolated from patients with new-onset T1DM induced a dramatic increase of interferon-γ secretion in GAD65 stimulated T cells.The percentage of plasmablasts in the spleen was increased with the progression of disease.Notably,plasmablast accumulated in the PLNs and islets of NOD mice with the progression of insulitis.Co-culture of islets from 5-week NOD mice with plasmablasts and T cells from 16-week NOD mice exacerbate β-cell apoptosis.Moreover,adoptive transfer of plasmablasts mixed with T cells from 16-week NOD mice into NOD/SCID mice accelerated the development of T1DM.In mice received plasmablast and T cell co-transfer,the severity of insulitis was much higher than recipients in the T cell transfer group and PBS group.Conclusions:Plasmablasts are increased and overactivated in the progression of T1DM.Plasmablasts play a vital role in immune disturbance by activation of diabetogenic T cells,further exacerbating destruction of pancreatic β-cells and promote the development of T1DM.This study firstly demonstrates that plasmablast is the pathogenic B cell subset in T1DM,which expands the knowledge of T1DM pathogenesis.Plasmablasts may serve as a novel therapeutic target for T1DM.