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The precise mechanisms by which the adaptor CARD9 facilitates resistance to bacterial infection remain unclear. Lin and colleagues document a role for CARD9 in the production of microbicidal reactive oxygen species.
In regulatory T cells, a decrease in expression of the transcription factor Foxp3 results in loss of suppressor function. Rudensky and co-workers find that Runx-CBFβ complexes are essential for maintaining Foxp3 expression in regulatory T cells.
Antibody-secreting cells switch expression of membrane-bound B cell antigen receptors to soluble immunoglobulin production by alternative mRNA polyadenylation. Milcarek and colleagues show that ELL2 and CstF-64 associate with RNA polymerase II to enhance promoter-proximal polyadenylation and immunoglobulin secretion.
Little is known about the transcription factors that facilitate NK cell differentiation. Brady and colleagues find that the basic leucine zipper transcription factor E4bp4 is essential for NK cell development in mice.
The role of Pellino proteins in Toll-like receptor (TLR) signaling is not completely understood. Sun and colleagues now find that Pellino1 ubiquitinates the signaling molecule RIP1 and is essential for TRIF-dependent TLR signal transduction in mice.
Several unconventional T cell populations, including γδ T cells and regulatory T cells, are selected by recognition of self antigen in the thymus. Craft and colleagues add TH-17 cells to the list of T cell subsets enriched by self-reactivity.
How signals through the pre–B cell antigen receptor (pre-BCR) and IL-7 receptor (IL-7R) coordinate population expansion of pre-B cells with subsequent recombination of the immunoglobulin κ-chain locus is unclear. Clark and colleagues show that pre-BCR signaling via the Ras-MEK-Erk pathway poises pre–B cells to undergo differentiation after escaping IL-7R signaling.
While promiscuous expression of tissue-specific antigens (TSAs) in the thymus is essential for self-tolerance, immunologically relevant TSA expression may also occur in the secondary lymphoid organs. A new study links the transcriptional regulator Deaf1 with altered TSA expression in the secondary lymphoid organs and autoimmune diabetes.
Like every metazoan species hosting a gut flora, drosophila tolerate commensal microbiota yet remain able to mount an efficient immune response to food-borne pathogens. New findings explain how the quantity of reactive oxygen species in the gut is 'tuned' to microbial burden and how intestinal immune homeostasis is thereby maintained.
Foxp3 expression is not stable and may be extinguished both in vitro and in vivo in regulatory T cells that convert into proinflammatory effector T cells. The loss of Foxp3 in regulatory T cells under autoimmune conditions may result in the conversion of suppressor T cells into highly autoaggressive lymphocytes.
Macrophages infected with human immunodeficiency virus type 1 emit long intercellular conduits that shuttle the viral protein Nef to bystander B cells, where it impairs cellular function and immunoglobulin class switching.
The authors recount their discovery of how pathogen-induced interleukin 12 production leads to TH1 T cell polarization. Simultaneously they discovered the suppressive cytokine interleukin 10 inhibits antigen-presenting cells, thus regulating development of TH1 cells.
Celiac disease is associated with HLA-DQ2.5 expression. Sollid and colleagues identify why this association exists by showing that binding of peptide to HLA-DQ2.5 is kinetically more stable.
Different pathogens induce different cytokine production via the C-type lectin DC-SIGN. Geijtenbeek and colleagues show that distinct carbohydrates on the pathogen surface induce the assembly and use of distinct DC-SIGN signaling complexes.
The intracellular 'biosensor' Nod2 responds to bacterial peptidoglycan by inducing activation of the transcription factor NF-κB. Bose and colleagues now find that Nod2 can also function as a cytoplasmic viral pattern-recognition receptor.