The end of the year is often a time for reflection. As we look back over the last year at Nature Reviews Immunology, we are struck by the diversity of topics we have covered, from interferons and nuclear receptors to somatic hypermutation and receptor editing. We have touched on B cells, neutrophils and mast cells, and have examined molecules such as dectin-1 and caspases. A major goal in understanding how all these components fit together in the immune system is the development of therapeutic strategies — a recurring theme in the journal. Our final issue of the year continues in this vein.

With the sharp increase in the prevalence of asthma in recent years, its development and treatment have become the focus of much research. On page 953, Dale Umetsu and Rosemarie DeKruyff propose that there might be another source of the T-helper-2-type cytokines that are produced by MHC-class-II-restricted CD4+ T cells in asthma: invariant natural killer T cells, which share characteristics with conventional CD4+ T cells, might have a crucial role in regulating the development of asthma. We also highlight a recent report (page 877) that discusses whether an effective strategy in the treatment of asthma might be to target another cell type — lung dendritic cells.

Norman Letvin reviews what we have learned from recent experiments in terms of the development of an effective AIDS vaccine, and what obstacles must still be overcome (page 930). And finally, in their Review on page 895, Roberto Gazzinelli and Eric Denkers examine the therapeutic potential of the interaction between protozoan parasites (infection by which is an issue of particular importance in developing countries) and Toll-like receptor signalling pathways.