Expression and Functions of the CB(2) Receptor in Human Leukocytes

The cannabinoid CB(2) receptor was cloned from the promyeloid cell line HL-60 and is notably expressed in most, if not all leukocyte types. This relatively restricted localization, combined to the absence of psychotropic effects following its activation, make it an attractive drug target for inflammatory and autoimmune diseases. Therefore, there has been an increasing interest in the past decades to identify precisely which immune cells express the CB(2) receptor and what are the consequences of such activation. Herein, we provide new data on the expression of both CB(1) and CB(2) receptors by human blood leukocytes and discuss the impact of CB(2) receptor activation in human leukocytes. While the expression of the CB(2) mRNA can be detected in eosinophils, neutrophils, monocytes, B and T lymphocytes, this receptor is most abundant in human eosinophils and B lymphocytes. We also review the evidence obtained from primary human leukocytes and immortalized cell lines regarding the regulation of their functions by the CB(2) receptor, which underscore the urgent need to deepen our understanding of the CB(2) receptor as an immunoregulator in humans.