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( p3 h5 M6 E2 p5 o3 ^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.: p3 n+ A( R' v5 K1 S
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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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% m0 j' m8 A3 l& Y/ v8 SWorking with naive mouse T cells, a team led by Alain Trautmann of the InstitutCochin de Génétique Moleculaire in Paris, France, saw similar results: greater survival and low-level proliferation in the T cells. "In the normal life of a lymphocyte, it will interact repeatedly with dendritic cells," Trautmann says. "These repeated meetings are essential for survival." To their surprise, the authors also detected a structure known as an immunological synapse at the junction between the cells. The synapse normally forms when a dendritic cell stimulates a T cell, but its formation was thought to require antigen.8 m* Y( W& g& C
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Both groups agree that cellular contact may boost the immune system's readiness in two ways. By stimulating survival and slow reproduction, the interaction may help maintain stocks of T cells. And the low level of stimulation provided by dendritic cells seems to prime lymphocytes for action. However, Martin believes that the work also exposes a possible downside. He thinks that the surge in cytokine production may increase the risk of autoimmune diseases like multiple sclerosis in susceptible individuals. "The interaction may set up a certain environment that is conducive to the pro-inflammatory reactions that you see in autoimmune diseases," he says.0 j5 B$ w. j* ]; h* Q, L' W+ y" Y/ \
: J$ t# |( F: o. f0 ~References:- e7 |3 z% s, G: ?. _: r2 e
, K' `- x5 p6 H! T/ c8 g& ]Kondo, T., et al. 2001. Nat. Immunol. 2:932–938.* E- P/ g) z# ]& u
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Revy, P., et al. 2001. Nat. Immunol. 2:925–931.
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Mitch(Even antigen-less dendritic cells can si) |
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发表于 2009-3-5 23:35
发表于 2015-5-25 16:01
