Efficient generation of immune cell memory can arise even in the absence of prior immunization or immunologic experience, according a new paper published in the May 2006 issue of Nature Immunology. "Memory-like" killer T cells can develop upon transfer into mice that lack such immune cells. These memory-like cells prove to be as effective as "true" memory cells, which arise upon immunization or infection, in mediating protection against bacteria.
The new findings by Jameson and colleagues counter existing controversy on whether 'memory-like' immune cells are functional in eliciting protection against pathogens. Previous work has demonstrated naive immune cells transferred into animals with lymphopenia -- a condition in which the body contains very few immune cells -- expand and develop many characteristics of memory cells even in the absence of any offending pathogen. Lymphopenia can arise due to a multitude of causes, including cancer treatments or by infection with viruses such as HIV that deplete immune cells.
Work by Jameson and colleagues demonstrates that killer cells from both normal and lymphopenic conditions protect against pathogen attack and that both require the usual developmental signals from 'helper' T cells. This work speaks directly to those developing bone marrow transplantation therapies aimed towards restoring the immune system of immunodepleted individuals. The new findings suggest that killer cells might effectively defend people with diseases that cause severe lymphopenia.
Stephen C Jameson (University of Minnesota Health Center, Minneapolis, MN, USA)
Abstract available online.
(C) Nature Immunology press release.
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