Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain
the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in
Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles
and JavaScript.
Three reactions diversify antibody genes in human somatic cells of the B lineage: VDJ recombination, somatic hypermutation and class-switch recombination. The discovery of activation-induced cytidine deaminase (AID) has led to the elucidation of a unified molecular mechanism for initiation of the last two reactions and suggests why B cells undergoing these reactions are prone to cancer-associated DNA damage.
A study in mice traces the path of West Nile virus into the brain. Viral replication in peripheral tissues triggers a Toll-like receptor inflammatory response that alters the blood-brain barrier (pages 1366–1373).
Drug discovery is either an exact business that is based on detailed knowledge of target structure or it is a fishing expedition that uncovers new drugs through screening of random compounds for their biological effect on target function. Isolation of a new p53 activator with anticancer properties strengthens the reputation of this second approach (pages 1321–1328).
Gallstones develop in response to an imbalance of lipids in bile, the digestive fluid produced in the liver. A compound that restores the balance prevents gallstone formation in mouse models (pages 1352–1358).
The US Food and Drug Administration has approved only one therapy for ischemic stroke, recombinant tissue plasminogen activator (tPA), which can increase blood flow to damaged brain tissue—but it can also have severe side effects and must be administered shortly after stroke. Experiments combining the drug with activated protein C (APC) may provide a solution (pages 1379–1383).