On the cover: Islets infected with indoleamine 2,3-dioxygenase (IDO) adenovirus are transplanted under the kidney capsule. Then the kidney is fixed, paraffin-embedded, sectioned, and stained for IDO expression. The image shows IDO expression by islet grafts. Liu, Z., H. Dai, N. Wan, T. Wang, S. Bertera, M. Trucco, and Z. Dai. 2007. Suppression of memory CD8 T cell generation and function by tryptophan catabolism. J. Immunol. 178: 4260–4266.