CB2 Receptors
Definition: CB2 receptors are cannabinoid receptors found mainly on immune cells and in tissues like the spleen. They help regulate inflammation and immune responses. Unlike CB1 receptors in the brain, activating CB2 doesn’t cause a high, which makes CB2 a major research target for anti-inflammatory and pain treatments.
Where Are CB2 Receptors Found?
CB2 receptors are most common on white blood cells, including B cells, natural killer cells, and macrophages, and in immune organs like the spleen and tonsils. They also appear at lower levels in the brain, mostly on microglia, the brain’s immune cells, where they become more active during inflammation or injury.
What Do CB2 Receptors Do?
When endocannabinoids activate CB2, immune cells tend to dial down the release of inflammatory signals. Researchers think this helps the body keep inflammation in check and resolve it once a threat has passed. CB2 was cloned in 1993, five years after CB1 was identified.
What Activates CB2 Receptors?
- Endocannabinoids: especially 2-AG
- THC: binds CB2 as well as CB1
- Beta-caryophyllene: a peppery terpene that selectively activates CB2, as shown in a 2008 PNAS study
CBD has low direct affinity for CB2 and appears to affect it indirectly.
Are There CB2-Based Medicines?
Not yet. Drug developers have studied CB2-targeted compounds for pain, inflammation, and neurodegenerative disease because they could offer benefits without a high. So far, none has been approved.
Related terms: Cannabinoid Receptors, CB1 Receptor, Caryophyllene, Cannabinoids
Sources: Lu HC, Mackie K, “An Introduction to the Endogenous Cannabinoid System,” Biological Psychiatry, 2016; Gertsch J et al., “Beta-caryophyllene is a dietary cannabinoid,” PNAS, 2008.
