Aberrant zonal recycling of germinal center B cells impairs appropriate selection in lupus

Systemic autoimmunity is driven by the production of pathogenic autoantibodies that can arise from germinal centers (GCs). Typically, B cells that acquire autoreactivity following somatic hypermutation in the GC die of neglect, but in autoimmunity these autoreactive clones still receive T cell help, driving aberrant selection. GC B cells cycle between the dark zone (DZ), where proliferation and mutation occur, and the light zone (LZ) where selection occurs. Temporal assessment comparing GCs from mice with chronic infection or lupus revealed a shared accumulation of LZ B cells while lupus GC B cells had a unique reduction in proliferation and a progressive loss of MYC and FOXO1 in lupus. This loss in proliferative capacity coincided with a reduction in B cell receptor repertoire diversity and mutational burden. Furthermore, we identified persistent dominant GC B cell clones associated with an expansion in plasma cell differentiation throughout disease. Together, our findings suggest that lupus disease progression is characterized by an inability for proper LZ selection, preventing zonal recycling, thereby driving the permissive selection and differentiation of autoreactive B cells. Germinal center (GC) B cells were sorted from the spleens of 3 B6.SLE1.yaa mice for each timepoint of 2 months (pre-disease), 4 months (disease onset), and 6 months (disease onset). 6000 GC B cells from each mouse were barcoded with hashtag antibodies, pooled, processed through the 10X RNA/V(D)J kit, and sequenced with the 10x Genomics Noavaseq 6000. Data was aligned to mm10 reference genome with cellranger ver.XXX. Output scRNA-seq FASTQ files were processed using Immcantations pipelines from Kleinstein Lab pREST0 and Change-O for BCR alignment and V(D)J alignment respectively, and Seurat (v.5.0.1) was used to analyze gene expression data to determine differences in GC B cell gene expression, V(D)J sequences, and BCR repertoire at different stages of the onset of lupus.