Project description:Protective immune responses to many pathogens depend on the development of high affinity antibody-producing plasma cells in germinal centers. Transgenic models suggest that there is a stringent affinity-based barrier to plasma cell development. Whether a similar high affinity barrier regulates plasma cell development under physiologic circumstances, and the nature of the plasma cell fate decision has not been defined precisely. Here we use a fate mapping approach to examine the relationship between germinal center (GC) B cells selected to undergo additional rounds of affinity maturation, germinal center pre-plasma cells and plasma cells. The data show that initial plasma cell selection overlaps with germinal center B cell selection, but that the plasma cell compartment accumulates a less diverse and higher affinity collection of antibodies over time. Thus, whereas the GC continues to diversify over time, affinity-based pre-plasma cell selection sieves the germinal center to enable accumulation of a more restricted group of high affinity antibody secreting plasma cells.
Project description:Humoral immunity requires the generation of high-affinity antibodies, which involves the generation of germinal centres (GC) promoting class switch and affinity maturation of antigen-specific B cells, and the differentiation of long-lived plasma cells. This multi-layered process is tightly controlled by the activity of a transcriptional network including Bcl6, essential for the development of GC, and Blimp1, required for the differentiation of plasma cells. Here, we reveal an additional layer of complexity by demonstrating that dynamic changes in E-protein activity mediated by Id3 govern both GC and plasma cell differentiation. We show that down-regulation of Id3 expression in B cells in essential for releasing E2A and E2-2, the combined activity of which is required for both GC B cell and plasma cell differentiation. We demonstrate that this pathway controls the expression of multiple key factors required for antigen-induced B cell differentiation, including Blimp1, Xbp1, Mef2b and CXCR4 and is therefore critical for establishing the transcriptional network that controls GC B cell and plasma cell differentiation. Genome binding of transcription factor E2A
Project description:Humoral immunity requires the generation of high-affinity antibodies, which involves the generation of germinal centres (GC) promoting class switch and affinity maturation of antigen-specific B cells, and the differentiation of long-lived plasma cells. This multi-layered process is tightly controlled by the activity of a transcriptional network including Bcl6, essential for the development of GC, and Blimp1, required for the differentiation of plasma cells. Here, we reveal an additional layer of complexity by demonstrating that dynamic changes in E-protein activity mediated by Id3 govern both GC and plasma cell differentiation. We show that down-regulation of Id3 expression in B cells in essential for releasing E2A and E2-2, the combined activity of which is required for both GC B cell and plasma cell differentiation. We demonstrate that this pathway controls the expression of multiple key factors required for antigen-induced B cell differentiation, including Blimp1, Xbp1, Mef2b and CXCR4 and is therefore critical for establishing the transcriptional network that controls GC B cell and plasma cell differentiation. Transcriptional profiling of wild type, Id3 knockout and E2A/E22 double knockout B cells using RNA sequencing
Project description:The Germinal center is a dynamic microenvironment wherein B cells expressing high affinity antibody variants produced by hypermutation are selected for clonal expansion by limiting numbers of T follicular helper cells. Although a great deal is known about the mechanisms that control B cell selection in the germinal center, far less is understood about the clonal behavior of the T follicular helper cells that regulate this process. Here we report on the dynamic behavior of clones of T follicular helper cells during the germinal center reaction. We find that like germinal center B cells, T follicular helper cells undergo antigen dependent selection during the germinal center reaction resulting in differential proliferative expansion and contraction. Increasing the amount of antigen presented in the germinal center leads to increased T follicular cell division. Competition between T follicular helper cell clones is mediated by T cell receptor affinity for peptide-MHC ligand. Higher affinity T cells expanding preferentially in the germinal center show increased expression of genes downstream of the T cell receptor, genes required for metabolic reprogramming, cell division and cytokine production. These dynamic changes lead to dramatic remodeling of the functional T follicular cell repertoire during the germinal center reaction.
Project description:The transcriptional repressors BCL6 and BACH2 are crucial regulators of germinal center (GC) B-cell fate, and are known to interact and repress transcription of PRDM1, a key driver of plasma cell differentiation. How these factors cooperate is not fully understood. Herein we show that while GC formation is only minimally impaired in Bcl6+/- or Bach2+/- mice, double heterozygous Bcl6+/-Bach2+/- mice exhibit profound reduction in GC formation. Splenic B-cells from Bcl6+/- Bach2+/- mice display accelerated plasmacytic differentiation and high expression of key plasma cell genes such as Prdm1, Xbp1 and CD138. ChIP-seq revealed that in B-cells BACH2 is mostly bound to genes together with its heterodimer partner MAFK. The BACH2-MAFK complex binds to sets of genes known to be involved in the GC response, 60% of which are also targets of BCL6. Approximately 30% of BACH2 peaks overlap with BCL6 including cis-regulatory sequences of the PRDM1 gene. BCL6 also modulates BACH2 protein stability and their protein levels are positively correlated in GC B-cells. Therefore, BCL6 and BACH2 cooperate to orchestrate gene expression patterning in GC B cells through both transcriptional and biochemical mechanisms, which collectively determine the proper initiation and timing of terminal differentiation. ChIP-seq using P18 antibodies in OCI-Ly7 cells
Project description:The transcription factor Pax5 represses B-lineage-inappropriate genes and activates B-cell-specific genes in B-lymphocytes. Here we have identified 170 novel Pax5-activated genes. Conditional mutagenesis demonstrated that the Pax5-regulated genes require continuous Pax5 activity for normal expression in pro-B and mature B cells. Expression of half of the Pax5-activated genes is either absent or significantly reduced upon Pax5 loss in plasma cells. Direct Pax5 target genes were identified based on their protein synthesis-independent activation by a Pax5-estrogen receptor fusion protein. Chromatin immunoprecipitation (ChIP) of Pax5 together with chromatin profiling by ChIP-on-chip analysis demonstrated that Pax5 directly activates the chromatin at promoters or putative enhancers of Pax5 target genes. The novel Pax5-activated genes code for key regulatory and structural proteins involved in B cell signaling, adhesion, migration, antigen presentation and germinal center B cell formation, thus revealing a complex regulatory network, which is activated by Pax5 to control B cell development and function. Keywords: Chip-chip, cell type comparison comparison of Pax5-/-Rag2-/- vs Rag2-/- pro-B cells
Project description:The transcription factor Pax5 represses B-lineage-inappropriate genes and activates B-cell-specific genes in B-lymphocytes. Here we have identified 170 novel Pax5-activated genes. Conditional mutagenesis demonstrated that the Pax5-regulated genes require continuous Pax5 activity for normal expression in pro-B and mature B cells. Expression of half of the Pax5-activated genes is either absent or significantly reduced upon Pax5 loss in plasma cells. Direct Pax5 target genes were identified based on their protein synthesis-independent activation by a Pax5-estrogen receptor fusion protein. Chromatin immunoprecipitation (ChIP) of Pax5 together with chromatin profiling by ChIP-on-chip analysis demonstrated that Pax5 directly activates the chromatin at promoters or putative enhancers of Pax5 target genes. The novel Pax5-activated genes code for key regulatory and structural proteins involved in B cell signaling, adhesion, migration, antigen presentation and germinal center B cell formation, thus revealing a complex regulatory network, which is activated by Pax5 to control B cell development and function. Keywords: Chip-chip, cell type comparison comparison of Pax5-/-Rag2-/- vs Rag2-/- pro-B cells