T-cell checkpoint pathway (ICP)

The T-cell checkpoint pathway refers to a collection of inhibitory signaling routes that regulate the magnitude and duration of T-cell responses. These pathways, which include the PD-1/PD-L1 and CTLA-4/B7 axes, are fundamental for maintaining peripheral tolerance and preventing autoimmune reactions by dampening T-cell activity after an immune challenge. In many cancers, these pathways are hijacked; tumor cells or the surrounding microenvironment upregulate inhibitory ligands that bind to checkpoint receptors on T cells, leading to T-cell exhaustion and immune evasion. Therapeutic intervention with immune checkpoint inhibitors (ICIs)—primarily monoclonal antibodies—blocks these inhibitory signals, effectively releasing the brakes on the immune system to restore anti-tumor activity. While highly effective in treating various malignancies, these therapies can also lead to immune-related adverse events (irAEs) due to the systemic loss of immune regulation.

Other names

Immune checkpoint pathwayInhibitory checkpoint pathwayT-cell inhibitory signaling pathwayCo-inhibitory pathway

Immune checkpoint inhibition; blockade of inhibitory receptors (e.g., PD-1, CTLA-4, LAG-3) or their ligands (e.g., PD-L1) to restore T-cell effector function and enhance anti-tumor immunity.