About the Cover
Host immune defense comprises a hard-wired mechanism for immediate generalized responses called innate immunity, and a precise circuitry for mounting specific responses called adaptive immunity. Innate immune responses include the complement cascade, macrophages, natural killer cells, and dendritic cells. Components of adaptive immune responses include plasma cells, antibodies, and lymphocytes. The two systems operate in a highly interconnected manner. Cancer arises when immune recognition, innate, and adaptive immune responses by the host fail. The cover image depicts a schematic diagram of immune surveillance and cancer. For details, see the Masters of Immunology article by Hidde Ploegh on page 5 of this issue.
[The cover image was rendered by Tom DiCesare (Whitehead Institute for Biomedical Research), and was adapted from Ploegh, HL. Viral strategies of immune evasion. Science 1998;280:248–53.]

About the Master
Hidde L. Ploegh is a professor of biology at Massachusetts Institute of Technology and a member of the Whitehead Institute for Biomedical Research in Cambridge, MA; prior to this appointment, he directed the immunology graduate program (1997–2005) at Harvard Medical School. He received his PhD in 1981 from the University of Leiden, the Netherlands, and performed the research for his doctoral thesis in Jack Strominger's lab at Harvard. Prior to his affiliation with Harvard, Dr. Ploegh served as a junior group leader in the immunology division led by Klaus Rajewsky at the University of Cologne in Germany. Dr. Ploegh has published over 400 papers, with topics spanning the range from how viruses evade immune surveillance to how the host innate and adaptive immune responses distinguish self from non-self and how professional antigen-presenting dendritic cells sense the presence of antigens and instruct the immune response. The Ploegh lab has contributed significantly to research on how products of the major histocompatibility complex are assembled and delivered to help initiate immune responses.