Immune Checkpoint Molecules

Immune checkpoint molecules are crucial components of the immune system that regulate the intensity and duration of immune responses but have been usurped by cancer cells and pathogens to evade the immune system.

Immune checkpoint molecules are primarily involved in controlling T cell activity, which is a central component of the adaptive immune system. T cells are essential for recognizing and eliminating infected or abnormal cells. However, to prevent uncontrolled immune responses and autoimmunity, there are checkpoints or regulatory mechanisms in place. NK cells also use immune checkpoint molecules and other inhibitory receptors to regulate their activity.

One of the well-known immune checkpoint pathways is the programmed cell death protein 1 (PD-1) pathway and its ligands, PD-L1 and PD-L2. When these ligands bind to PD-1 on the surface of T cells, it inhibits T-cell activation and function, suppressing the immune response. Immune cells can express a variety of additional checkpoint molecules that regulate T cell activity, including CTLA-4, BTLA, LAG-3, Tim-3, TIGIT, PVRIG (CD112R), and VISTA (B7-H5).