Objectives B subsets. To study the correlation between the counts of B cell subsets and SLE activity, and their dynamics after treatment with rituximab.
Methods Rituximab in doses from 500 to 2000 mg was administered to 8 SLE patients with high and moderate disease activity (1 male and 7 females), 6 patients had lupus nephritis. The relative counts of CD19 + B cells, the total population of memory B cells (CD19 + CD27 +), “preswitch” (CD19 + IgD + CD27 +) and “postswitch” (CD19 + IgD-CD27 +) memory B cells, naive (CD19 + IgD + CD27-) and transitional (CD19 + IgD + CD10 + CD38 ++ CD27-) B cells, plasmablasts (CD19 + CD38 +++ IgD-CD27 + CD20-), short-lived plasma cells (CD19 +, CD38 +), long-lived plasma cells (CD19 + CD138 +), and double negative B-cells (CD19 + CD27-IgD-) were measured. All B cell subsets were determined by multi-color flow cytometry using a panel of monoclonal antibodies to B-lymphocytes' surface membrane markers. Statistical analysis was performed using the U Mann-Whitney test.
Results There was no statistically significant correlation between SLE activity and B-cell subsets counts before initiation of rituximab, most likely due to a small sample size. 2-12 scores decrease by SLEDAI2K scale in SLE activity from average 19±5 score “before” to average 11±4 scores “after” was documented already in 3 months after initiation of rituximab. This was accompanied by reduction of CD 19+ levels (median 6.25% (4.2 -10,5); 0,1% (0,05-1,5), (p =0,004;)), count of short-lived plasma cells (CD19 +, CD38 +) (median 5.5% (2,2-7,15); 0,15% (0-1,3), (p =0,008)), memory B cells (CD19 + CD27 +) (median 1% (0,8-3); 0,05% (0-0,4), (p =0,01)), and naive (CD19 + IgD + CD27-) B cells (median 42.6% (22,9-49,75); 14% (2,15-21,2), (p =0,01)). Residual CD19 + cells during severe depletion phase were mostly represented by “preswitch” (CD19 + IgD + CD27 +) and “postswitch” (CD19 + IgD-CD27 +) memory B cells, and double negative memory B cells (CD19 + CD27-IgD -).
Conclusions Reduction of SLE clinical activity is associated with accompanying decrease in the counts of short-lived plasma cells (CD19 +, CD38 +), memory B cells (CD19 + CD27 +), naive (CD19 + IgD + CD27-) B-lymphocytes, which most likely indicates that these cells are major targets for anti-B cell therapy, as well as key players in autoimmune process development and progression.
Disclosure of Interest None declared