The endocannabinoid system (ECS) consists of cannabinoid receptors types CB1 and CB2 and is an important neuromodulator system that regulates and controls many functions, including memory, learning, mood, addiction, inflammation, immune responses, and more. CB two receptors are primarily present in the immune system, with the greatest concentration found in the spleen. CB2 receptors are also present in the gastrointestinal tract, the reproductive system, immune cells, fat cells, the liver, and bones. Learn more about the endocannabinoid system, cannabinoids and cannabinoid receptors.