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Immunoglobulin class-switch recombination requires activation-induced cytidine deaminase. Chaudhuri and colleagues show independent recruitment of protein kinase A to switch regions, where it phosphorylates this deaminase to promote class-switch recombination.
CD40 signals induce the production of interleukin 12 and interleukin 10 in uninfected and Leishmania major–infected macrophages, respectively. Saha and colleagues suggest that L. major–induced cholesterol depletion facilitates the assembly of distinct CD40 signalosomes.
In worms, antimicrobial peptides contribute to the defense against pathogen infection. Ewbank and colleagues describe a noncanonical signaling pathway required for the induction of one particular family of antimicrobial peptides.
Genes induced by inflammatory stimuli are expressed in a precise temporal order. Baltimore and colleagues show that mRNA stability exerts strong influence over the kinetics of the induction of genes encoding inflammatory molecules.
Whether interleukin 23 (IL-23) affects the differentiation of or simply the maintenance of IL-17–producing helper T cells (TH-17 cells) is unclear. Cua and colleagues show that IL-23 is required for the full differentiation and proliferation of effector TH-17 cells in vivo.
The mechanism by which cytokines suppress Bax activation and eosinophil apoptosis are not well understood. Malter and colleagues pinpoint a function for the peptidyl-prolyl isomerase Pin1 in mediating cytokine-induced suppression of Bax activation.
Myeloid and lymphoid cells are derived from the same multipotent progenitor cell. Camargo and colleagues show that the transcription factor Mef2c restricts myeloid differentiation to favor production of B, T and natural killer cells.
The signals that regulate the development of natural killer T cells are not completely understood. Glimcher and colleagues document an essential function for the transcription factor Egr2 in the maturation of these cells.
The identity of the cytoplasmic DNA receptor that activates the inflammasome has remained elusive. Superti-Furga and colleagues use a proteomics screen to identity AIM2 as the DNA sensor for the inflammasome.
The biological function of the SLAM family receptor CRACC is not known. Using a CRACC-deficient mouse, Veillette and colleagues show that CRACC can activate or inhibit natural killer cells, depending on the availability of the adaptor EAT-2.
Leukocyte adhesion is governed by the affinity state of integrin LFA-1. Laudanna and colleagues show that many Rho GTPase family members interact to form a regulatory module that regulates LFA-1 activation.
Factors governing T cell homeostasis are poorly defined. Hedrick and colleagues find that the transcription factor Foxo1 maintains the homeostasis of naive T cells by regulating genes involved in T cell trafficking and survival.
Compared with naive CD8+ T cells, naive CD4+ T cells undergo inefficient homeostatic proliferation. Mackall and colleagues now attribute this difference to interleukin 7–mediated suppression of the expression of MHC class II on dendritic cells.
The C-type lectin dectin-1 induces T cell responses. Geijtenbeek and colleagues demonstrate that in human dendritc cells, dectin-1 ligands induce two independent signaling pathways that act in synergy at the point of activation of nuclear factor-κB.
Hypoxia incites inflammation, particularly at mucosal surfaces. Eltzschig and colleagues show that hypoxia also suppresses inflammation by inducing expression of the neuronal guidance molecule netrin-1, which inhibits the transepithelial migration of neutrophils.
The mechanism by which the coreceptor CD28 contributes to T cell activation is vague. Ghosh and colleagues find that CD28 facilitates NF-κB activation by regulating recruitment and phosphorylation of the kinase PDK1.