NF-κB regulates PD-1 expression in macrophages.

Area of Science:

• Immunology
• Molecular Biology
• Cell Biology

Background:

• Programmed cell death-1 (PD-1) is crucial for T cell exhaustion in chronic infections.
• PD-1 expression is observed in various immune cells post-activation.
• Mechanisms regulating PD-1 in cells beyond CD8 T cells are not well understood.

Purpose of the Study:

• To investigate the molecular mechanisms driving PD-1 induction in CD4 T cells, macrophages, and B cells.
• To compare PD-1 regulation across different immune cell types.
• To elucidate the signaling pathways involved in PD-1 gene activation.

Main Methods:

• TCR stimulation and calcineurin/NFAT pathway inhibition (cyclosporin A) in CD4 T cells.
• LPS, PMA, and ionomycin stimulation in macrophages and B cells.
• NF-κB binding site analysis and chromatin immunoprecipitation (ChIP) for NF-κB p65.
• Histone modification and CpG methylation analysis.

Main Results:

• CD4 T cell PD-1 induction requires the calcineurin/NFAT pathway, similar to CD8 T cells.
• Macrophage PD-1 induction by LPS is independent of the calcineurin/NFAT pathway and involves NF-κB signaling.
• B cells utilize both NFAT and NF-κB pathways for PD-1 expression, with higher levels induced by PMA/ionomycin.
• NF-κB binding to a conserved upstream region is essential for LPS-induced PD-1 activation in macrophages.
• Macrophage PD-1 induction involves accessible chromatin modifications but not loss of CpG methylation, unlike CD8 T cells.

Conclusions:

• Distinct signaling pathways regulate PD-1 expression in different immune cells.
• Toll-like receptor (TLR)/NF-κB signaling contributes to PD-1 induction in macrophages.
• Microbial infections may exploit PD-1 regulation to manipulate immune inhibitory responses.