Sci. Signal., 24 November 2009
Immunology T Cells Get the Nod
Nancy R. Gough
Science Signaling, AAAS, Washington, DC 20005, USA
Nod2 is a member of the nucleotide-binding oligomerization domain receptor (NLR) family, which binds microbial products to play a key role in the cells mediating the innate immune response to pathogens. Shaw et al. report that Nod2 also functions in T cells, which are part of the adaptive immune response, to mount an effective response to the intracellular parasite Toxoplasma gondii. Survival of Nod2-deficient mice after T. gondii infection was impaired compared with that of wild-type mice. Unexpectedly, survival of infected mice deficient for the caspase-recruitment domain–containing kinase Ripk2, which is required for Nod2 signaling in innate immune cells, was not compromised. Examination of cells from peritoneal exudates showed that both Nod2-deficient and wild-type mice had similarly low parasite loads at early stages of infection but that after 12 days the Nod2-deficient mice had a much higher infection burden. The Nod2-deficient mice showed reduced concentration of circulating interferon- (IFN-) 7 days after infection. Natural killer cells and T helper 1 (TH1) are two main sources of IFN-, a cytokine essential for an effective immune response. The NK cell response to infection appeared the same as wild type in the Nod2-deficient animals; however, the Nod2-deficient mice had many fewer TH1 cells. Various experiments with wild-type and Nod2-deficient dendritic cells and transfer of wild-type and Nod2-deficient T cells into recipient mice demonstrated that the defect in TH1 cells appeared to be intrinsic to the T cells and not a consequence of impaired dendritic cell function. Survival of Nod2-deficient mice in response to T. gondii infection was improved if the animals received wild-type T cells. Compared with wild-type T cells, Nod2-deficient T cells failed to produce sufficient interleukin-2 (IL-2), which is a critical cytokine for T cell differentiation, to promote T helper cell differentiation. The gene encoding IL-2 is a target of the transcription factor NF-B, and, when transfected into a fibroblast cell line, one subunit of NF-B (c-Rel), NF-B–inducing kinase (NIK), and Nod2 all coimmunoprecipitated together. Furthermore, when transfected into Jurkat T cells, maximal stimulation of an NF-B reporter gene occurred when all three (c-Rel, NIK, and Nod2) were expressed together, suggesting that the three proteins synergize to drive gene expression. Consistent with a defect in NF-B signaling, Nod2-deficient T cells exhibited decreased nuclear translocation of c-Rel after stimulation compared with wild-type cells. Thus, Nod2 appears to have a function in the adaptive immune system in T cell differentiation, and this role appears to be independent of its role as a pattern recognition receptor in the innate immune system (see Salek-Ardakani and Croft for commentary).
M. H. Shaw, T. Reimer, C. Sánchez-Valdepeñas, N. Warner, Y.-G. Kim. M. Fresno, G. Nuñez, T cell–intrinsic role of Nod2 in promoting type 1 immunity to Toxoplasma gondii. Nat. Immunol. 10, 1267–1274 (2009). [PubMed]
S. Salek-Ardakani, M. Croft, T cells need Nod too? Nat. Immunol. 10, 1231–1233 (2009). [PubMed]
Citation: N. R. Gough, T Cells Get the Nod. Sci. Signal. 2, ec375 (2009).
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