c-Jun NH₂-Terminal Kinase (JNK)1 and JNK2 Have Distinct Roles in CD8⁺ T Cell Activation

The c-Jun NH₂-terminal kinase (JNK) signaling pathway is induced by cytokines and stress stimuli and is implicated in cell death and differentiation, but the specific function of this pathway depends on the cell type. Here we examined the role of JNK1 and JNK2 in CD8⁺ T cells. Unlike CD4⁺ T cells, the absence of JNK2 causes increased interleukin (IL)-2 production and proliferation of CD8⁺ T cells. In contrast, JNK1-deficient CD8⁺ T cells are unable to undergo antigen-stimulated expansion in vitro, even in the presence of exogenous IL-2. The hypoproliferation of these cells is associated with impaired IL-2 receptor α chain (CD25) gene and cell surface expression. The reduced level of nuclear activating protein 1 (AP-1) complexes in activated JNK1-deficient CD8⁺ T cells can account for the impaired IL-2 receptor α chain gene expression. Thus, JNK1 and JNK2 play different roles during CD8⁺ T cell activation and these roles differ from those in CD4⁺ T cells.