Monday, November 6, 2006

Innate + Adaptive = Immunity

drj writes "Innate immunity is initiated by host cells recognizing stable molecular patterns associated with pathogenic microbes and viruses. These molecular patterns are thought to be reliable triggers because they are required for the life of the pathogen. Here, French et al. show that viruses can change these patterns and evade innate immunity in mice deficient in adaptive immune responses. Early infection by murine cytomegalovirus is controlled by natural killer (NK) cells, which use one form of Ly49H to recognize a viral protein, m157, that is expressed on infected cells. Mice possessing a form of Ly49H that is not activated by this virus die in 6 days. Recombinase-deficient mice without adaptive immunity efficiently suppress viral replication for only about 3 weeks, when they succumb. Viruses recovered from these mice do not trigger Ly49H+ NK cells and nearly all possess mutations in m157, probably allowing them to resist innate immunity. This paper demonstrates an essential role for adaptive immunity in clearing virus, thereby reducing the risk of a mutant evading the innate immune system. Even for this double-stranded DNA virus, mutations occur frequently enough to present a serious health risk. The authors suggest that cytomegalovirus disease, which develops more than a month after transplant in some immune suppressed recipients, may be due to a similar selection of mutant viruses escaping the innate immune response.
PubMed Escape of Mutant Double-Stranded DNA Virus from Innate Immune Control Anthony R. French, Jeanette T. Pingel, Markus Wagner, Ivan Bubic, Liping Yang, Sungjin Kim,Ulrich Koszinowski, Stipan Jonjic, and Wayne M. Yokoyama. Immunity, Vol. 20, 747–756, June, 2004

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