This volume in The Year in Immunology series focuses on reviews covering novel approaches to understanding immunoregulatory mechanisms and immune signaling. A wide range of topics is covered within this volume, including lineage determination of T cells, roles of various receptors in B cell activation, activation of basophils, micro-RNAs (miRNAs) in inflammation and immunity, and autoimmune disorders. NOTE: Annals volumes are available for sale as individual books or as a journal. For information on institutional journal subscriptions, please visit http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1749-6632. ACADEMY MEMBERS: Please contact the New York Academy of Sciences directly to place your order (www.nyas.org). Members of the New York Academy of Science receive full-text access to the Annals online and discounts on print volumes. Please visit http://www.nyas.org/MemberCenter/Join.aspx for more information about becoming a member.