Changes Of B Cell Subsets And The Underlying Mechanisms In Patients With Ulcerative Colitis

Background:Ulcerative colitis(UC)is a form of inflammatory bowel disease(IBD),and the precise etiology and the pathogenic process of UC remains unclear.To date,there is no treatment that provides a curative option and patients may suffer from long-lasting symptoms and are at risk of developing colitis-associated cancer(CAC).Focusing on the pathogenesis of UC is of great significance in finding new therapeutic targets.Risk factors including environment,genetic susceptibility,and in particular,overactive immune responses are associated with UC development.However,the role of B cell immunity in the pathogenesis of UC is poorly understood.Neither frequency nor activity of B cell subsets in active UC has been clarified.The immune balance between follicular regulatory T(TFR)cells and follicular helper T(TFH)cells is important in regulating B-cell responses.However,the alterations of TFR cells and TFR/TFH balance in UC remain unclear.Aim:We aimed to study the frequencies,phenotypic characterization,and function of different B cell subsets,TFR cells,TFH cells and the levels of related serum immunoglobulin(Ig)and cytokines in active UC patients.Furthermore,we explored the potential correlation between these cells and clinical parameters in patients with UC.This study is aimed at evaluating the role of B cell subsets in the pathogenesis of UC,and the mechanisms underlying perturbation of B cell immunity.Methods:Evaluating the frequencies and phenotypic characterization of the cell subsets by flow cytometry needs a big volume of peripheral blood.It will do harm to the patients if we do all the experiments using sample from a patient.Consequently,we use different groups of patients and HC for the 3 experiments below.1.Peripheral blood from 23 patients with active UC and 14 healthy controls(HC)were examined for the frequencies of different subsets of memory B cells and plasmablasts by flow cytometry.The levels of serum Ig,including IgG,IgA,and IgM were measured using cytometric bead array(CBA).2.Peripheral blood from 25 patients with active UC and 15 HC was examined for Breg subsets by flow cytometry.Intestinal tissue of 5 patients with UC and 5 controls was also examined for Breg cells.The levels of serum interleukin(IL)-10 were measured using ELISA(enzyme-linked immunosorbent assay),and the levels of serum Igwere measured using CBA.IL-10 production in B cells isolated from patients with UC was examined.3.Peripheral blood from 25 UC patients and 15 HC was examined for the frequencies of circulating B,TFR,TFH,and Treg cells by flow cytometry.Levels of serum cytokines and Igwere measured using CBA.For all the patients participated in the experiments above,disease activity was evaluated by the Mayo clinic score,and CRP and ESR were measured in individual subjects.Potential associations among the values of different measures were analyzed by the Spearman correlation test.Results:1.In comparison with that in HC,significantly reduced frequencies of IgG~+IgD~-CD27~+CD19~+ memory B cells and increased frequencies of CD20-CD19~+ plasmablast subsets were detected in UC patients,accompanied by higher serum IgG levels.The values of Mayo clinic score,CRP,or ESR in UC patients were negatively correlated with the frequencies of IgG~+IgD~-CD27~+CD19~+ memory B cells,while positively correlated with the frequencies of plasmablast subsets and the serum IgG levels.Furthermore,the concentrations of serum IgG,and the frequencies of plasmablasts were negatively associated with the frequencies of IgG~+IgD~-CD27~+CD19~+ memory B cells.The serum IgG levels were positively associated with the frequencies of CD138+CD38+CD20-CD19~+,and IgG~+CD38+CD20-CD19~+ plasmablasts.2.Compared to HC,significantly reduced frequencies of CD24highCD38 high and CD5~+ Bregs were detected in UC patients,accompanied by lower serum IL-10 levels.IL-10 production was significantly decreased in stimulated B cells from patients with UC,whereas patient IL-10+ B cells were found to be enriched in CD24highCD38 high and CD5~+ B cells.However,increased percentages of CD95~+ exhausted Breg cells were encountered in subsets.The values of Mayo clinic scores,CRP,or ESR in UC patients were negatively correlated with the frequency of Bregs and the IL-10 levels,while positively correlated with the frequency of CD95~+ exhausted Breg cells.Furthermore,the concentrations of serum IL-10 were positively associated with the frequencies of CD24highCD38 high Breg cells,and serum IgG levels were positively associated with the percentages of CD95~+ exhausted cells in Breg cells.3.Compared to HC,significantly reduced frequencies of Foxp3+CXCR5~+ TFR cells,the subset IL-10+Foxp3+CXCR5~+ cells,and Treg cells,but increased frequencies of Foxp3-CXCR5~+ TFH cells,and IL-21+Foxp3-CXCR5~+ subset were detected in UC patients,accompanied by lower levels of serum IL-10 and elevated levels of serum IL-21 and IgG.The values of Mayo clinic score,CRP,or ESR in UC patients were negatively correlated with the frequencies of TFR cells and TFR/TFH ratio,while positively correlated with the frequencies of TFH cells and the serum IL-21 levels.Furthermore,the frequencies of IgG~+ plasmablasts was negatively correlated with the frequencies of TFR cells,and the serum IgG levels were negatively correlated with TFR/TFH ratio.Conclusions:1.Active UC is characterized by overactive B cell response,and exhaustion of regulatory control in the B cell compartment,which involved in the pathogenic process of UC.2.Alterations in TFR and TFH shift the balance between immunogenic state and immune tolerance,contribute to dysregulated B cell immunity,and the pathogenesis of UC.