This month's issue of Nature Reviews Immunology reflects the breadth of the field. Two review articles focus on the roles of specific proteins in immune responses. On page 781, David Raulet outlines our present knowledge of the function of NKG2D and how signalling through this receptor — the ligands of which are upregulated by infected, transformed and stressed cells — alerts the host to the presence of infected or damaged cells. NKG2D was first identified in a search for genes that are preferentially expressed by natural killer cells, and this has inspired our cover image this month. The interactions of SAP (signalling lymphocytic activation molecule (SLAM)-associated protein) with SLAM receptors and their role in immune responses are reviewed by Pablo Engel and colleagues on page 813. SAP is either defective or absent in patients with X-linked lymphoproliferative syndrome (XLP).
Migration and homing is a key aspect of an effective immune response, and two articles cover this topic this month. On page 822, Eric Kunkel and Eugene Butcher review how chemokines and adhesion molecules work together to control the migration of plasma cells from secondary lymphoid tissue to the target tissue. And a Highlight article on page 777 describes the results of three papers showing that, in addition to chemokines and adhesion molecules, leukotriene B4 has a role in the migration of T cells.
