Marijuana may suppress immune functions

COLUMBIA, S.C., Nov. 26 (UPI) -- A team of international immunologists led by a U.S. researcher says it found smoking marijuana can trigger a suppression of the body's immune functions.

Dr. Prakash Nagarkatti of the University of South Carolina says the researchers studied cannabinoids -- a group of compounds found in the marijuana, or cannabis, plant, including THC, or delta-9 tetahydrocannabinol -- already used for medical purposes.

"Cannabis is one of the most widely used drugs of abuse worldwide and it is already believed to suppress immune functions, making the user more susceptible to infections and some types of cancer," Nagarkatti says in a statement. "We believe the key to this suppression is a unique type of immune cell, which has only recently been identified by immunologists, called myeloid-derived suppressor cells."

Most immune cells fight infection and cancer to protect the host, but myeloid-derived suppressor cells actively suppress the immune system. The presence of these cells is known to increase in cancer patients and some say myeloid-derived suppressor cells may suppress the immune system against cancer therapy, Nagarkatti says.

The study, published in the European Journal of Immunology, demonstrated cannabinoids can trigger a massive number of myeloid-derived suppressor cells through activation of cannabinoid receptors that may suppress the immune system by activating these unique cells.

"These results raise interesting questions on whether increased susceptibility to certain types of cancers or infections caused from smoking marijuana results from induction of myeloid-derived suppressor cells," Nagarkatti says.