Stayin' alive, without antigen

When a T cell meets a dendritic cell that carries an antigen, the meeting activates the T cell to battle pathogens. Less certain is what happens when the dendritic cell doesn't have antigen. Now, two reports bolster the controversial hypothesis that this kind of antigen-free cell-to-cell contact is necessary for the survival of T cells.

Roland Martin and colleagues of the National Institute of Neurological Disorders and Stroke in Bethesda, MD, found that contact with an antigen-free dendritic cell provokes dramatic changes in human memory T cells—though not as profound as activation by an antigen. Gene expression shifts, boosting production of cytokines such as interferon gamma, and some T cells begin to divide slowly. Most importantly, the meeting lengthens the life of memory cells, more than doubling the percentage that survive five days in culture.

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