Novel specialized cell state and spatial compartments within the germinal center

Abstract

Within germinal centers (GCs), complex and highly orchestrated molecular programs must balance proliferation, somatic hypermutation (SHM) and selection to both provide effective humoral immunity and to protect against genomic instability and neoplastic transformation. In contrast to this complexity, GC B cells are canonically divided into two principal populations, dark zone (DZ) and light zone (LZ) cells. We now demonstrate that following selection in the LZ, B cells migrated to specialized sites within the canonical DZ that contained tingible body macrophages (TBMs) and were sites of ongoing cell division. Proliferating DZ (DZp) cells then transited into the larger DZ to become differentiating DZ (DZd) cells before re-entering the LZ. Multidimensional analysis revealed distinct molecular programs in each population commensurate with observed compartmentization of non-compatable functions. These data provide a new three-cell population model that both orders critical GC functions and reveals essential molecular programs of humoral adaptive immunity.

Permissive selection followed by affinity-based proliferation of GC light zone B cells dictates cell fate and ensures clonal breadth

“…However, we are currently unable to identify spatial distribution of cells in each cMyc + subpopulation due to technical limitations. Recently, a proliferative CXCR4 + CD83 + GC B cell subset, “grey zone (GZ) B cells,” has been discovered with a new gating strategy, and this subset is transcriptionally distinct from the rest of GC B cells, namely CXCR4 neg CD83 + LZ B cells and CXCR4 + CD83 neg DZ B cells ( 54 ). Approximately one-third and two-thirds of GZ B cell subset are LZ B cells (CXCR4 neg/+ CD83 + ) and DZ B cells (CXCR4 + CD83 neg/+ ), respectively, when cells are delineated using the conventional gating strategy ( 54 ).…”

Negative feedback by NUR77/Nr4a1restrains B cell clonal dominance during early T-dependent immune responses

“…Critical signals supplied by Tfh to LZ GC B cells in turn drive further clonal expansion in the DZ or selection into long-lived memory and plasma cell compartments (Mesin et al, 2016). Interestingly, publicly available datasets of GC B cell gene expression reveal enrichment of Nr4a1 -and many of its target genes that we have previously identified and validated -among LZ GC B cells ( Figure 1C) (Kennedy et al, 2020). Conversely, almost half of all genes that are repressed by NUR77 in B cells are also enriched for this LZ gene signature ( Figure 1D, Supplemental Data 1-Tables 1-3, Supplementary Figure 1),…”

“…Transcripts enriched in Nr4a1 -/-B cells relative to WT following 2 hr BCR stimulation were identified from a recently published RNAseq data set (Tan et al, 2020) (Kennedy et al, 2020) was used as a template to establish an LZ "gene signature"; genes enriched in LZ and DZ (excluding 'gray zone') were identified as >1.5-fold upregulated relative to each other with p <0.05 via prior analysis using EdgeR (Supplemental Data 1- Table 2). Nr4a1 target genes were compared to both of these LZ and DZ gene signatures and presented in Figure 1; Supplemental Data 1- Table 3).…”

Intrarenal B cells integratein situinnate and adaptive immunity in human renal allograft rejection

“…We do not know if TLS-mediated selection usually results in high-affinity and specific antibodies. Furthermore, it is not clear if the GC B cell molecular programs are recapitulated in TLS (Kennedy et al, 2020). Finally, we do not know if B cells can be selected in inflamed tissue in the absence of histologically obvious TLS.…”

“…In germinal center (GCs), spatial and molecular orchestration of clonal expansion, somatic hypermutation (SHM) and selection drive production of high affinity antibodies and immunological memory (Kennedy et al, 2020;Victora and Nussenzweig, 2012). Remarkably, in many inflammatory and autoimmune diseases, GC-like structures form in afflicted organs (tertiary lymphoid structures, TLS) (Leslie, 2016).…”