This volume in The Year in Immunology series focuses on reviews covering novel approaches to our understanding of immunoregulatory mechanisms. 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 plasmactyoid dendritic cells * Micro-RNAs (miRNAs) in inflammation and immunity * Autoimmune disorders NOTE: Annals volumes are available for sale as individual books or as a journal. For information on institutional journal subscriptions, please visit www.blackwellpublishing.com/nyas. 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.