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Recently, we reported that CD40-/- mice, exhibiting exclusively T cell-independent IgA class switch recombination (CSR), demonstrated near normal levels of IgA plasma cells in the gut lamina propria (LP), despite the complete lack of germinal centers (GCs). In this study, we have extended our analysis focusing on how to reconcile these findings using flow cytometry and molecular markers for IgA CS

Gut-derived antigens trigger immunoglobulin A (IgA) immune responses that are initiated by cognate B cells in Peyer’s patches (PPs). These cells colonize the subepithelial domes (SEDs) of the PPs and subsequently infiltrate pre-existing germinal centers (GCs). Here we defined the pre-GC events and the micro-anatomical site at which affinity-based B cell selection occurred in PPs. Using whole-organ

By mutational analysis of the octamer-TATA box intervening region in the mouse SP6 κ promoter, we have mapped two octamer-dependent, costimulatory regions, A and B. The A region was active in late B cells only, while the B region was active throughout B cell differentiation. The B region was TATA proximal and contained a heptamer and an E box of the E2A type that is common in Vκ promoters. Mutatio

Conflicting findings have recently been presented as to the sites and sources of B cells that undergo class switch recombination (CSR) to IgA in the gut. In this study we provide compelling evidence in CD40-/- mice demonstrating that IgA CSR can be independent of CD40 signaling and germinal center formation and does not occur in the gut lamina propria (LP) itself. We found that CD40-/- mice had ne

The ultimate goal for vaccination is to stimulate protective immunological memory. Protection against infectious diseases not only relies on the magnitude of the humoral immune response, but more importantly on the quality and longevity of it. Adjuvants are critical components of most non-living vaccines. Although little attention has been given to qualitative aspects of the choice of vaccine adju

The meninges are important for brain development and pathology. Using single-cell RNA sequencing, we have generated the first comprehensive transcriptional atlas of neonatal mouse meningeal leukocytes under normal conditions and after perinatal brain injury. Weidentified almost all known leukocyte subtypes and found differences between neonatal and adult border-associated macrophages, thus highlig

Matrix protein 2 ectodomain (M2e) is considered an attractive component of a broadly protective, universal influenza A vaccine. Here we challenge the canonical view that antibodies against M2e are the prime effectors of protection. Intranasal immunizations of Balb/c mice with CTA1-3M2e-DD-generated M2e-specific memory CD4 T cells that were I-A d restricted and critically protected against infectio

The immune system is dysfunctional for years after hematopoietic stem cell transplantation (HSCT). A potential cause is an intrinsic B cell deficiency. In a cohort of pediatric HSCT patients few CD27+ B cells formed after transplantation with the number of CD27+IgMhigh cells more affected than class-switched ones. A previously unacknowledged population of CD27-IgMhigh cells made up the majority of

Immunoglobulin κ promoters show sequence divergence but conserved function between different subgroups. Here we show that three separate 5' elements are required for synergistic stimulation of transcription with the decamer in a κ promoter. These sites are a 5' E-box, a 3' AT-rich region in the pentadecamer (pd) element, and the κ-Y element. Elf-1 is a novel κ-Y element ligand induced upon mitogen

The intact SP6 χ promoter stimulated transcription 30 times more efficiently than did a control promoter consisting of a TATA motif as the only promoter element. Mutation of the SP6 χ promoter decamer in two positions reduced the transcriptional stimulation activity by over 90%. Promoters containing the SP6 χ promoter octamer or a consensus octamer in front of a TATA box were ineffective immunoglo

A prime function of the mucosal immune system is the production of secretory immunoglobulin (Ig) A antibodies. To initiate this, the organized lymphoid system is strategically located at sites where mucosal antigens are encountered. The follicle-associated epithelium (FAE) hosts specialized cells called M cells that effectively take up antigen. After transport of antigen via the FAE, the mucosal-a

Multiple DNA polymerases exist in eukaryotes. Polymerases α, δ and ε are mainly responsible for chromosomal DNA replication in the nucleus and are required for proliferation. In contrast, the repair polymerases β and η are not essential for cellular proliferation in yeast or mice, but a lack of either polymerase can lead, respectively, to defects in base excision repair or the ability to replicate

The GAGA box of the rat serine protease inhibitor 2 (spi 2) genes not only acts as a basal promoter element, but also mediates transcriptional activation by growth hormone and interleukin-6. The GAGA box is separated from the TATA box by only 12 bp, and this close association is required for efficient transcription. Hence, the GAGA box may influence transcription efficiency through interactions be

The SP6 κ-promoter pentadecamer (pd) element was found to be unable to stimulate transcription when present in one copy as the only promoter element in a minimal promoter but showed weak stimulatory activity when present as a multimer (four copies). One copy of the pd element acted synergistically with an octamer element, but not with a SP1 site, to stimulate transcription. The effect was orientat

The gut immune system protects against mucosal pathogens, maintains a mutualistic relationship with the microbiota, and establishes tolerance against food antigens. This requires a balance between immune effector responses and induction of tolerance. Disturbances of this strictly regulated balance can lead to infections or the development inflammatory diseases and allergies. Production of secretor

DNA interstrand cross-links (ICLs) are the most cytotoxic lesions to eukaryotic genome and are repaired by both homologous recombination-dependent and -independent mechanisms. To better understand the role of lesion bypass polymerases in ICL repair, we investigated recombination-independent repair of ICLs in REV3 and REV1 deletion mutants constructed in avian DT40 cells and mouse embryonic fibrobl

The catalytic subunit of polymerase ζ is encoded from the Rev3 gene. The enzyme is conserved through eukaryotic evolution and its main function appears to be translesion synthesis (TLS) over damaged bases that stall DNA replication. In non-vertebrate cells, inactivation of polymerase ζ results in a moderate hypersensitivity to DNA damage but no proliferative defect in the absence of exogenous dama

The germinal center (GC) reaction in Peyer′s patches (PP) requires continuous access to antigens, but how this is achieved is not known. Here we show that activated antigen-specific CCR6+CCR1+GL7− B cells make close contact with M cells in the subepithelial dome (SED). Using in situ photoactivation analysis of antigen-specific SED B cells, we find migration of cells towards the GC. Following antig

During the last two decades our understanding of human B cell differentiation has developed considerably. Our understanding of the human B cell compartment has advanced from a point where essentially all assays were based on the presence or not of class-switched antibodies to a level where a substantial diversity is appreciated among the cells involved. Several consecutive transitional stages that

The physiological mechanism for producing antigen-specific antibodies is based on a two-phase neo-Darwinian process: the first phase consists of diversity generation (formation of the repertoire), and the second phase is antigen-mediated selection. In this article, we consider how the natural immunoglobulin gene-diversification processes can be exploited both in vivo and in vitro in order to allow