Infectious diseases remain a serious medical burden in both
developing and industrialized countries. The emergence of
new diseases such as HIV/AIDS and severe acute respiratory
syndrome (SARS), the resurgence of known diseases such as
West Nile disease and multidrugresistant tuberculosis, and
the threat of deliberately developed man-made infections are
cause for concern. When vaccines or effective treatments are
not available, we rely on the immune system to clear the host
of infectious agents and disease. A better understanding of
the tactics used by pathogens and of the immune system�s defensive
armoury is needed to pave the way for improved strategies
of prevention and therapy. The four articles in this Insight
provide a snapshot of the issue, addressing in turn the nature
and spread of emerging and re-emerging infectious diseases,
the assault strategies used by major pathogens, the immediate
innate immune response, and the antigen-specific acquired
(or adaptive) immune response, which is the host�s second
line of defence.
David Morens, Gregory Folkers and Anthony Fauci review new
and old infectious diseases that pose challenges for public
health in the twenty-first century. Scott Merrell and Stanley
Falkow discuss the strategies that pathogens use to evade
the host�s defences and secure their own survival. Bruce Beutler
reviews the role of Toll-like receptors (TLRs) in early detection
of and defence against pathogens in relation to clinical applications,
and discusses how TLRs may contribute to autoimmunity and
sterile inflammation. And Marianne Boes and Hidde Ploegh review
successive stages of T-cell activation from a cellbiological
perspective, discussing how functional data obtained in
vitro may translate to an in vivo setting.
These articles provide an overview of the current status
of each field,
and consider directions for future research. We are indebted
to the
authors who contributed to this Insight, and we hope that
you will find
the reviews informative and stimulating.