Over the past few years, everyone's expectations of what web sites can do have increased tremendously. In response to these increased expectations, we have redesigned our web site, and we hope that the 'new look' Nature Reviews Immunology web site, which was launched at the beginning of December, has made our content more accessible. As you can see in this issue of 2006, we have also redesigned our print copy to achieve the same goal.

Sensing and responding to changes in the environment is not the sole preserve of Nature Reviews Immunology, and in this issue, we have four articles on receptors that are used by cells of the immune system to sense their environment. On page 33, Gordon Brown discusses how recognition of β-glucan carbohydrates that are present mainly in the cell walls of fungi by the cell-surface receptor dectin-1 affects the immune system. Recognition of microbial components also occurs intracellularly, and on page 9, Warren Strober and colleagues review the signalling pathways that emanate from the nucleotide-binding oligomerization domain (NOD) proteins NOD1 and NOD2 (which are intracellular sensors of bacterial peptidoglycan) and discuss how mutant forms of these proteins might result in disease.

In contrast to sensors of microbial components, the signalling lymphocytic activation molecule (SLAM) family of receptors mediates homotypic interactions. On page 56, André Veillette discusses the mechanisms by which SLAM family receptor ligation is signalled to the cell and how defects in these signalling pathways are associated with immune defects.

On page 44, Christopher Glass and Sumito Ogawa discuss how signalling through nuclear receptors, in particular the glucocorticoid receptor, the peroxisome-proliferator-activated receptors (PPARs) and the liver X receptors, modulates inflammation and immunity.