Smoking marijuana can trigger the suppression of the body’s immune functions, revealing why users are more susceptible to certain cancers and infections, according to a new study by an international team of immunologists.
The team, led by Dr. Prakash Nagarkatti from the University of South Carolina, focused their research on cannabinoids, a group of compounds found inside the cannabis plant, including THC or delta-9 tetahydrocannabinol, which is already used legally in some places for medical purposes, such as pain relief.
Nagarkatti said the research is important because cannabis is one of the most widely used drugs worldwide. He believes cannabis triggers suppression of a unique type of immune cell, that has only recently been identified by immunologists, called myeloid-derived suppressor cell (MDSCs.)
In a healthy immune system, immune cells fight against infections and malignant cells to protect the host. MDSCs work in the opposite way to actively suppress the immune system. These cells are known to increase in cancer patients and the researchers believe they may even suppress the immune system to hinder cancer therapies as well as actually promote cancer growth.
While the research raises interesting questions about marijuana use increasing susceptibility to certain types of cancer or infections, the results could be beneficial to a large number of other clinical disorders where immune system suppression and cannabinoids' anti-inflammatory properties are desirable, such as arthritis, lupus, hepatitis, some allergies and multiple sclerosis, said Nagarkatti.
“In these, your immune system gets activated and starts destroying your own cells and tissues. You have to try to suppress your immune response,” he said. “In such instances, there is a need to develop drugs that can suppress the immune response.”
In a related study, Dr. Christian Vosshenrich from the Institut Pasteur in Paris, showed when cancer cells grow they produce a molecule called interleukin-1β, which also triggers MDSCs. This study identifies how MDSCs produced during cancer growth also weakens the ability of immune cells to kills cancer cells.