Programmed cell death-1 (PD-1) is responsible for T cell exhaustion during chronic viral infections and is expressed on a variety of immune cells following activation. Despite its importance, the mechanisms that regulate PD-1 in cell types other than CD8 T cells are poorly defined. In this study, the molecular mechanisms for inducing PD-1 expression in CD4 T cells, macrophages, and B cells were explored. In CD4 T cells, PD-1 induction following TCR stimulation required NFAT, as the calcineurin/NFAT pathway inhibitor cyclosporin A was able to block PD-1 induction in a manner similar to that seen in CD8 T cells. In contrast, LPS but not PMA and ionomycin stimulation was able to induce PD-1 expression in macrophages in a manner insensitive to cyclosporin A–mediated inhibition. B cells could use both pathways, although the levels of PD-1 expression were highest with PMA and ionomycin. An NF-κB binding site located upstream of the gene in conserved region C was required for NF-κB–dependent PD-1 gene activation in macrophages. Chromatin immunoprecipitation showed NF-κB p65 binding to this region following stimulation of macrophages with LPS. PD-1 induction was associated with histone modifications characteristic of accessible chromatin; however, in contrast to CD8 T cells, conserved region B in macrophages did not lose CpG methylation upon stimulation and PD-1 expression. The linkage of TLR/NF-κB signaling to the induction of PD-1 suggests the possibility of an opportunistic advantage to microbial infections in manipulating immune inhibitory responses.
CITATION STYLE
Bally, A. P. R., Lu, P., Tang, Y., Austin, J. W., Scharer, C. D., Ahmed, R., & Boss, J. M. (2015). NF-κB Regulates PD-1 Expression in Macrophages. The Journal of Immunology, 194(9), 4545–4554. https://doi.org/10.4049/jimmunol.1402550
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