An Ets element regulates the transcription of the human 2B4 gene in natural killer cells

AP-1 transcription factors in cytotoxic lymphocyte development and antitumor immunity

The proper functioning of cytotoxic lymphocytes, such as natural killer and CD8+ T cells, is essential for effective cancer-immunity and immunotherapy responses. The differentiation of these cells is controlled by several transcription factors (TFs), including members of the activator protein (AP)-1 family. The activity of AP-1 family members is regulated by various immune signaling pathways, which can be triggered by activating or inhibitory receptors as well as cytokines. The target genes controlled by AP-1 TFs are central to generate immunity to pathogens or malignancies. Here, we provide an overview of the current understanding of how AP-1 TFs regulate cytotoxic lymphocytes.

Human natural killer cell receptor 2B4 (CD244) down-regulates its own expression by reduced promoter activity at an Ets element

2B4 (CD244), a member of the CD2 subset of the immunoglobulin superfamily, is important for stimulating human natural killer (NK) cell cytotoxicity and cytokine production. It is expressed on all NK cells, a subpopulation of T cells, monocytes, basophils and eosinophils. 2B4 interaction with its ligand CD48 regulates NK, T and B lymphocyte functions and thus plays a central role in various immune responses. Previous study indicated a role for AP-1 and Ets in the transcription of the 2B4 gene. In this study we report that stimulation of NK cells through surface 2B4 down-regulates its own expression due to a reduction in the promoter activity at the Ets element. The down-regulation of 2B4 could be a mechanism to attenuate the co-stimulatory signal from 2B4--CD48 interactions.

IL-2/IL-18 prevent the down-modulation of NKG2D by TGF-β in NK cells via the c-Jun N-terminal kinase (JNK) pathway

TGF-beta is known to play a major role for the reduced NKG2D expression seen in cancer patients. However, the mechanisms for reduced TGF-beta-induced down-regulation of NKG2D are unclear. In this study, we observed that IL-2/IL-18 increased the NKG2D expression in the TGF-beta treated NK cell line in a dose-dependent manner. Incubation with the JNK inhibitor SP600125 inhibited the NKG2D expression induced by IL-2/IL-18 in the TGF-beta treated human NK cell line. Moreover, the NK cytotoxicity assay showed that the reduced NK cytotoxicity by TGF-beta was recovered by IL-2/IL-18 treatment. The results indicate that IL-2/IL-18 strongly prevented the TGF-beta-induced NKG2D down-regulation in NK cells via the JNK pathway. Taken together, the protected expression of NKG2D by IL-2/IL-18 provides insight into the mechanism of NKG2D regulation and it also supplied useful information for creating a novel therapeutic approach to treat TGF-beta-secreting cancer cells.