Application Of Lymphocyte B Subgroup In Monitoring Disease Activity In Patients With Systemic Lupus Erythematosus Treated With Belimumab Combined With Conventional Regimen

Systemic lupus erythematosus（SLE）is a systemic autoimmune disease characterized with serum multiple autoantibodies and multiple organs involvement.B cells play a critical role in the pathogenesis of SLE.Excessive activation of B cells and obstacles to the clearance of autoreactive B cells lead to the production of various autoantibodies,which in turn cause systemic autoimmune inflammation and organ damage.Studies have found that patients with SLE exhibit abnormalities in various B cell subsets.Belimumab（BLM）is a monoclonal antibody against B cell activating factor（BAFF）and is the first biologic approved for the treatment of SLE.It is recommended for SLE patients with insufficient control（ongoing disease activity or frequent flares）to first-line treatments and inability to taper glucocorticosteroid（GC）dosage to an acceptable levels（ie,maximum of 7.5 mg/day）.As an Add-on treatment,BLM takes effect slowly.Predicting and monitoring the efficacy of BLM is a recent research hotspot.At present,some studies have focused on the changes in the proportion of B cell subsets in patients after using BLM to treat SLE,but there is no research report on the possibility of B cell subsets for monitoring the disease activity of SLE after BLM treatment.Objective To detect the changes of B cell subsets by flow cytometry in patients with SLE who had be treated with BLM.To analyzed the correlation between the clinical manifestations,laboratory results,disease activity score and B cell subsets in the 6 mouths follow up to explore whether the B cell subsets can be used as biomarker for monitoring disease activity of SLE patients treated by BLM.Methods Twenty SLE patients who were treated with BLM combined with standard treatment in the Affiliated Hospital of Inner Mongolia Medical University from January 1,2021 to September 30,2021 were enrolled.Clinical manifestation,laboratory result,serum BAFF concentration and the proportion of B cell subsets was collected and analyzed at the time of the baseline and 4,8,12,16,20,and 24 weeks after the treatment.The changes before and after treatment,the correlation between the clinical manifestations,laboratory results,disease activity score,response according to the remission criteria SLE Responder Index-4（SRI-4）and B cell subsets were analyzed to identify whether and which B cell subset could be used for disease activity monitoring in the patients treated by BLM.Results1.Compared with healthy controls,resting na（?）ve B cell subsets（CD19⁺CD10^-CD27^-IgD⁺CD38⁺）,activated na（?）ve B cell subsets（CD19⁺CD10^-CD27^-IgD⁺CD38^-）,memory B cell subsets（CD19⁺CD10^-CD27⁺）,class-switched memory B cell subsets（CD19⁺CD10^-CD27⁺IgD^-）,double negative memory B cell subsets（CD19⁺CD10^-CD27^-IgD^-）,plasma cell subsets(CD19⁺CD10^-CD27⁺IgD^-CD38⁺⁺)was significantly increased in peripheral blood of SLE patients,while the non-class-switched memory B cell subsets（CD19⁺CD10^-CD27⁺IgD⁺）was significantly decreased.2.Anti-double-stranded DNA antibody titers,24-hour urine protein,and disease activity score had decreased significantly,while serum complement C3 and C4 levels had increased significantly after the treatment of BLM combined with standard therapy.Meanwhile,the dosage of oral GCs had significantly reduced.3.After the treatment of BLM,the resting na（?）ve B cell subsets（CD19⁺CD10^-CD27^-IgD⁺CD38⁺）,activated na（?）ve B cell（CD19⁺CD10^-CD27^-IgD⁺CD38^-）,double negative memory B cell（CD19⁺CD10^-CD27^-IgD^-）ratio decreased significantly,while the ratio of immature B cell subsets（CD19^-CD10⁺CD27^-CD38⁺）,memory B-cell（CD19⁺CD10^-CD27⁺）,non-class-switched memory B cell（CD19⁺CD10^-CD27⁺IgD⁺）,class-switched memory B cell（CD19⁺CD10^-CD27⁺IgD^-）,plasma cell(CD19⁺CD10^-CD27⁺IgD^-CD38⁺⁺)and absolute T cell counts were not significantly changed.4.Further analysis of the correlation between each B cell subset and serum BAFF concentration,laboratory results,disease activity scores showed that the proportion of double negative memory B cell（CD19+CD10^-CD27^-IgD^-）was significantly positively correlated with anti-dsDNA antibody titer,SLEDAI-2k score and 24-hour urine protein.The proportion of activated na（?）ve B cell subsets（CD19+CD10^-CD27^-IgD⁺CD38^-）was significantly positively correlated with anti-dsDNA antibody titer and SLEDAI-2k score.Meanwhile,there was a significant positive correlation between serum BAFF concentration and anti-dsDNA antibody titer.5.By comparing the differences of laboratory results and the proportion of B cell subsets at baseline in patients who met or did not meet the SRI-4 remission criteria,it was found that in the SRI remission group the anti-dsDNA antibody titer,SLEDAI-2k,serum BAFF concentration,the proportions of activated na（?）ve B cell（CD19⁺CD10^-CD27^-IgD⁺CD38^-）and double negative memory B cell subsets（CD19⁺CD10^-CD27^-IgD^-）were significantly higher than those in the group that did not meet the SRI remission criteria.The 24-hour urine protein in the group that achieved SRI remission was significantly lower than the baseline level in the group that did not achieve SRI remission.Conclusion 1.BLM can ameliorate serological results and reduce the early stage B cell subsets;2.Double-negative memory B cell subset and activated na（?）ve B cell subset held promise for the disease activity monitoring in the SLE patients treated with BLM.