IL4 and IL21 cooperate to induce the high Bcl6 protein level required for germinal center formation.

Bcl6 (B-cell lymphoma 6) is a transcriptional repressor and critical mediator of the germinal center reaction during a T-cell-dependent antibody response, where it enables somatic hypermutation of immunoglobulin genes and inhibits terminal differentiation via repression of Blimp1. It can also contribute to the development of diffuse large B-cell lymphoma when expressed inappropriately. Bcl6 regulation is mediated both at the transcriptional and post-transcriptional levels, and in particular a strong signal through the B-cell receptor causes rapid proteasomal degradation of Bcl6.

The transcription factors IRF8 and PU.1 negatively regulate plasma cell differentiation.

Activated B cells undergo immunoglobulin class-switch recombination (CSR) and differentiate into antibody-secreting plasma cells. The distinct transcriptomes of B cells and plasma cells are maintained by the antagonistic influences of two groups of transcription factors: those that maintain the B cell program, including BCL6 and PAX5, and plasma cell-promoting factors, such as IRF4 and BLIMP-1. We show that the complex of IRF8 and PU.

The BTB-ZF transcription factor Zbtb20 is driven by Irf4 to promote plasma cell differentiation and longevity.

The transcriptional network regulating antibody-secreting cell (ASC) differentiation has been extensively studied, but our current understanding is limited. The mechanisms of action of known "master" regulators are still unclear, while the participation of new factors is being revealed. Here, we identify Zbtb20, a Bcl6 homologue, as a novel regulator of late B cell development.

Oct2 and Obf1 as Facilitators of B:T Cell Collaboration during a Humoral Immune Response.

The Oct2 protein, encoded by the Pou2f2 gene, was originally predicted to act as a DNA binding transcriptional activator of immunoglobulin (Ig) in B lineage cells. This prediction flowed from the earlier observation that an 8-bp sequence, the "octamer motif," was a highly conserved component of most Ig gene promoters and enhancers, and evidence from over-expression and reporter assays confirmed Oct2-mediated, octamer-dependent gene expression. Complexity was added to the story when Oct1, an independently encoded protein, ubiquitously expressed from the Pou2f1 gene, was characterized and found to bind to the octamer motif with almost identical specificity, and later, when the co-activator Obf1 (OCA-B, Bob.

Germinal center-independent, IgM-mediated autoimmunity in sanroque mice lacking Obf1.

Mice homozygous for a point mutation in the Rc3h1 gene encoding Roquin1, designated sanroque mice, develop a severe antibody-mediated autoimmune condition. The disease is T-cell intrinsic, exacerbated by macrophage-intrinsic defects and driven by excessive T follicular helper cell generation and spontaneous germinal centre (GC) formation. This culminates in abnormally high numbers of plasma cells secreting high-affinity autoreactive immunoglobulin G (IgG).

B and T cells collaborate in antiviral responses via IL-6, IL-21, and transcriptional activator and coactivator, Oct2 and OBF-1.

A strong humoral response to infection requires the collaboration of several hematopoietic cell types that communicate via antigen presentation, surface coreceptors and their ligands, and secreted factors. The proinflammatory cytokine IL-6 has been shown to promote the differentiation of activated CD4(+) T cells into T follicular helper cells (T(FH) cells) during an immune response. T(FH) cells collaborate with B cells in the formation of germinal centers (GCs) during T cell-dependent antibody responses, in part through secretion of critical cytokines such as IL-21.

Blimp1 is limiting for transformation in a mouse plasmacytoma model.

Multiple myeloma (MM) and plasmacytomas are cancers of antibody-secreting cells (ASCs). PRDM1/BLIMP1 is an essential regulator of ASC development. Histologic evidence shows that 100% of MM expresses PRDM1/BLIMP1, indicating that PRDM1/BLIMP1 is important for the development or persistence of MM.

Oct2 enhances antibody-secreting cell differentiation through regulation of IL-5 receptor alpha chain expression on activated B cells.

Mice lacking a functional gene for the Oct2 transcriptional activator display several developmental and functional deficiencies in the B lymphocyte lineage. These include defective B cell receptor (BCR) and Toll-like receptor 4 signaling, an absence of B-1 and marginal zone populations, and globally reduced levels of serum immunoglobulin (Ig) in naive and immunized animals. Oct2 was originally identified through its ability to bind to regulatory regions in the Ig loci, but genetic evidence has not supported an essential role for Oct2 in the expression of Ig genes.

Initiation of plasma-cell differentiation is independent of the transcription factor Blimp-1.

Blimp-1 is considered an essential regulator of the terminal differentiation of B cells into antibody-secreting plasma cells. We show here that Rag1-/- mice reconstituted with fetal liver cells homozygous for a DNA-binding-deficient mutant of Prdm1 (the gene encoding Blimp-1) lack a defined plasma-cell compartment, yet show detectable amounts of all immunoglobulin isotypes. In vitro analysis revealed that Blimp-1 is not required for the initiation of antibody secretion but is essential for subsequent high immunoglobulin production.

Normalization of boutique two-color microarrays with a high proportion of differentially expressed probes.

Normalization is critical for removing systematic variation from microarray data. For two-color microarray platforms, intensity-dependent lowess normalization is commonly used to correct relative gene expression values for biases. Here we outline a normalization method for use when the assumptions of lowess normalization fail.

The Ets factor Spi-B is a direct critical target of the coactivator OBF-1.

OBF-1 (Bob.1, OCA-B) is a lymphoid-specific transcriptional coactivator that associates with the transcription factors Oct-1 or Oct-2 on the conserved octamer element present in the promoters of several ubiquitous and lymphoid-specific genes. OBF-1-deficient mice have B cell-intrinsic defects, lack germinal centers, and have severely impaired immune responses to T cell-dependent antigens.