They give marijuana the ability to reduce inflammation. They are part of the reason why marijuana has medical benefits.
First of all, tonsils, white blood cells, and the spleen contain CB2 receptors. Cannabinoids activate CB2 receptors. As a result, CB2 receptors release chemicals throughout the body. Because CB2 receptors release chemicals throughout the body, certain bodily functions occur, like inflammation reduction.
Inflammation is a factor in many conditions and diseases. Inflammation is often painful and can further complicate diseases and conditions.