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In lymph nodes, cellular positioning can dictate the immune response. Lund and colleagues show that nematode infection triggers interactions between lymphotoxin-producing B cells and CXCR5+ dendritic cells and CD4+ T cells to initiate T helper type 2 responses.
The pleiotropic cytokine TGF-β is involved in the generation of Treg cells and maintaining tolerance. Zhang and Bevan show that TGF-β acts specifically to block the proliferation of low-affinity T cells independently of effects on the development of Treg cells.
Whether cross-interference between innate immune receptors affects the outcome of immune responses remains unclear. Taniguchi and colleagues show that RLR activation interferes with activation of the Il12b promoter induced by TLR signaling.
Notch signaling is known to modulate macrophage polarization. Hu and colleagues show that the Notch–RBP-J axis controls the expression of M1 macrophage–specific genes by promoting translation of the transcription factor IRF8.
Dock8 deficiency leads to defects in humoral immunity. Geha and colleagues show that Dock88 interacts with MyD88 to bridge TLR9 signaling to the Src-Syk-STAT3 pathway to promote B cell proliferation and differentiation.
Activated B cells can tailor their ensuing antibody responses by isotype switching. McHeyzer-Williams and colleagues demonstrate B cell–intrinsic requirements for the transcription factors T-bet and RORα in maintaining IgG2a+ and IgA+ memory cells, respectively.
Positive selection of thymocytes is controlled by TCR expression and signaling. Lu and colleagues describe a previously uncharacterized protein, Tespa1, which associates with TCR signaling components and has a critical role in positive selection.
The eukaryotic translation-initiation factor eIF4E is a rate-limiting factor in protein translation. Sonenberg and colleagues show that phosphorylation of eIF4E modulates the antiviral response by selectively stimulating translation of the NF-κB inhibitor IκBα
TRIM28 is a nuclear protein associated with repressive heterochromatin. Honjo and colleagues show that loss of TRIM28 in T cells alters peripheral T cell homeostasis and regulatory T cell function, which leads to autoimmunity.
Polarized CD4+ T cells can demonstrate considerable plasticity depending on the cytokine milieu they encounter. O'Shea and colleagues show that retinoic acid induces the microRNA miR-10a, which suppresses the transcription factor Bcl-6 to prevent conversion into follicular helper T cells.
The role of costimulation in negative selection is controversial. Singer and colleagues demonstrate that it is critical for clonal deletion and its absence results in the diversion of thymocytes to an intraepithelial lymphocyte population.
Major histocompatibility complex (MHC) molecules are known to mediate reverse signaling. Cao and colleagues show that reverse signaling via MHC class I attenuates Toll-like receptor–triggered innate inflammatory responses through an Fps–SHP-2 pathway.
The aminopeptidase ERAAP trims peptides loaded onto MHC class I molecules and can be targeted during evasion of the immune response by pathogens. Shastri and colleagues show that inhibition of ERAAP identifies a protective nonclassical MHC presentation pathway involving Qa-1.
The processes that underlie maintenance of the identity of regulatory T cells are unclear. Sun and colleagues show that expression of the ubiquitin-conjugating enzyme Ubc13 by these cells is critical for this process.
Discriminating between pathogens and commensals is a major dilemma faced by the immune system. Nunez et al. demonstrate that the recognition of bacterial pathogen type III secretion systems by the NLRC4 inflammasome is key to this discrimination.
The Immunological Genome Project aims to build a comprehensive database of gene-expression and gene-regulatory networks in the mouse immune system. Here Turley and colleagues analyze the transcriptomes of lymph-node stromal cells under steady-state and inflammatory conditions.
As part of the Immunogical Genome project, Kang and colleagues compare the gene-expression profiles of emergent thymocytes from adult mice that express the γδ T cell antigen receptor, segregated on the basis of the use of the γ- or δ-chain variable region, and find that the main subsets are molecularly distinct.
Follicular helper T cells provide help to cognate B cells in germinal centers to boost humoral immunity. Nutt and colleagues generate IL-21–GFP reporter mice to track the fate of follicular helper T cells.
Periodontitis is associated with aging and more neutrophil-mediated tissue pathology. Hajishengallis and colleagues show an inverse correlation between interleukin 17 expression and Del-1 expression in gingival tissues, with Del-1 protecting tissues from neutrophil infiltration.
Neutrophils are early responders and must navigate using spatial cues to arrive at infection sites. Xu and colleagues show that the opposing activities of MAP kinases Erk and p38 govern neutrophil migration.