Volume 13 Issue 5, May 2012

In the gut, cells of the immune system must tolerate commensal bacteria but also detect pathogens. To achieve this, intestinal phagocytes are hyporesponsive to Toll-like receptor stimulants released from commensals, but can detect invasion of pathogens via the intracellular NLRC4 inflammasome.

Gene profiling by the Immunological Genome Project consortium has identified distinct transcriptional programs that determine the migratory and functional fates of emerging γδ thymocytes.

Interleukin-17 (IL-17) induces the recruitment of neutrophils to sites of inflammation. In a model of periodontitis, Del-1 is now described to be an inhibitor of IL-17 expression that suppresses the recruitment of neutrophils and the associated inflammation-mediated pathology.

The identification of the natural lipids that select invariant natural killer T cells (iNKT cells) in vivo has been somewhat elusive and controversial. A new study shows that ether-bonded phospholipids, generated mainly in peroxisomes, are responsible for the development of a major subpopulation of iNKT cells.

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.

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.

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.

The identity of the self lipids presented by CD1d that select iNKT cells is controversial. De Libero and colleagues identify ether-bonded self lipids generated by the peroxisome enzyme GNPAT can select developing iNKT cells in the thymus.

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.

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.

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.