Cannabinoid receptor type 2 (CB2)

The cannabinoid receptor type 2, or CB2, is a G protein-coupled receptor found mainly on immune cells, where it influences inflammation and immune-cell movement.

CB2 was identified after CB1 and shares about half of its amino acid sequence. Rather than brain tissue, it is concentrated in the spleen, tonsils, bone marrow and on circulating white blood cells such as macrophages and B cells. Activation by endocannabinoids, most strongly 2-AG, tends to reduce the release of inflammatory cytokines and change how immune cells migrate. CB2 is also expressed at low levels by microglia and some neurons, and its expression rises in tissues under inflammatory stress.

Because CB2 activation does not cause intoxication, it has drawn interest as a target for inflammation and pain research, though no CB2-selective drug has reached approval. CBD is not a classic CB2 agonist; its affinity for the receptor is low, and any influence on CB2-associated pathways described in laboratory studies appears to be indirect. Human evidence remains limited.