Development in Motion: Helper T Cells at Work

In mammals, helper T cells orchestrate defense against diverse pathogens. However, these warriors of the immune system can also result in self-inflicted injury culminating in autoimmune and allergic diseases. Recent findings—such as the discovery of the Th17 lineage—have revealed additional complexity in the fates chosen by helper T cells and have begun to reshape our view of how signaling and transcriptional networks generate appropriate and inappropriate immunity.