Dendritic cells (DCs) interact with naïve T cells in the presence of antigens to initiate primary immune responses, but it is know known whether this interaction also occurs in the absence of antigens. Two reports in October Nature Immunology describe the importance for the maintenance of protective immunity of a low-level activation of T cells by the dendritic cells themselves, even in the absence of pathogens.

Takayuki Kondo and colleagues from the US National Institutes of Health investigated the DC-mediated signal from the T cell surface to the nucleus and found a pattern of activation in T cells that correlates with increased in vitro survival. These effects are caused exclusively by DCs and are associated with antigen-independent gene expression for cytokines such as interferon-gamma (Nat Immunol 2001, DOI: 10.1038/ni711).

In a separate study, Patrick Revy and colleagues from Institut Cochin de Génétique Moléculaire, Paris, found that in the absence...

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