CB2 receptor: definition, immune functions and therapeutic potential

CB2 receptors, or cannabinoid type 2 receptors, are an important component of the endocannabinoid system, a biological network of endocannabinoids, receptors and enzymes with which cannabis interacts. This type of cannabinoid receptor is expressed mainly in the body's immune system cells, while CB1 receptors are highly concentrated in the brain and nervous system. It is thought that CB2 receptors may play a role in regulating immune system responses, such as inflammation.

What are CB2 receptors?

CB2 receptors refer to a specific type of cannabinoid receptor present in the body. These receptors enable us to experience the subjective and therapeutic effects of cannabis by interacting with its compounds, such as THC and CBD. A cannabis terpene, caryophyllene, also appears to interact with CB2 receptors.

CB2 receptors form part of what is known as the endocannabinoid system. The function of this endocannabinoid system is to maintain our body's equilibrium - or homeostasis - and involves various enzymes, receptors and natural cannabis-like compounds called endocannabinoids.

When we consume cannabis, the body receives chemical compounds that interact with CB2 receptors and catalyze effects in the body, such as reducing inflammation. Similar in structure to cannabis cannabinoids, the body naturally produces compounds called endocannabinoids that also interact with cannabinoid receptors. These endocannabinoids include chemicals such as’anandamide and 2-AG.

Caryophyllene: the only CB2 agonist terpene

The beta-caryophyllene (β-caryophyllene) is a terpene present in high concentrations in many cannabis strains (GSC, Rockstar, OG Kush), but also in black pepper, cloves and basil. It is the only terpene known to bind directly to a cannabinoid receptor - in this case CB2, of which it is a partial agonist.

This property has two important implications:

Firstly, it partly explains the’entourage effect, caryophyllene contributes to the anti-inflammatory effects of cannabis independently of CBD or THC, via its own CB2 activation.

Secondly, it opens up new prospects for products topical, When absorbed through the skin, caryophyllene can activate CB2s in the skin without passing through the systemic circulation, providing local anti-inflammatory action without any psychoactive effect.

What do CB2 receptors do?

CB2 receptors are thought to play a role in regulating immune signaling and inflammatory responses throughout the body. Some cannabinoids are thought to have anti-inflammatory effects via CB2 receptors, whose activation alters the way inflammatory signals are transmitted. Unlike CB1 receptors, which are abundant in the brain and associated with the sensation of euphoria, CB2 receptors are more evenly distributed throughout the body, in the cells of the immune system.

Contrary to popular belief, the CBD does not bind readily to CB2 receptors; CBD has a low affinity for CB2. It also has a low affinity for CB1, but CBD interacts with these receptors in a non-direct way by influencing related systems.

The difference between CB1 and CB2 receptors

CB1 and CB2 receptors are the two most widely studied cannabinoid receptor types, but there are others. Both types of receptor are present throughout the body, but their local concentration differs somewhat: CB1 receptors are very present in the brain, central nervous system and lungs, while CB2 receptors are more abundant in the immune system.

Activation of these two types of receptor seems to have different regulatory functions. The CB1 receptors appear to play a role in regulating a wide range of homeostatic functions influencing sleep, appetite, memory, mood and sensory experience, among others. CB2 receptors are thought to be involved in functions related to immune and inflammatory signaling.

CB1 and CB2 receptors also differ in structure, which affects the way cannabinoids interact with them. For example, THC binds strongly to CB1 receptors but weakly to CB2 receptors.