Cannabis May Suppress Immune System

April 15, 2003 -- Cannabis may offer hope to people with autoimmune disorders such as lupus and rheumatoid arthritis. Cannabis seems to decrease inflammation in the body by suppressing certain parts of the immune system. Researchers are hoping this finding will lead to new treatments.

Previous studies have hinted at immune system abnormalities among cannabis users -- specifically, in the function of immune system cells called T lymphocytes and natural killer cells. While these cells help the body fight infections, no direct link with lowered immunity has yet been shown.

In this study, researchers tested the blood of 29 cannabis smokers -- 13 occasional users and 16 regular users (weekly or daily use). They compared the results with a group of 32 nonsmokers.

Again, researchers found that cannabis smokers had fewer immune-enhancing natural killer cells and lymphocytes, and higher levels of a protein that may promote tumor growth, called interleukin-10.

These changes can dampen the immune system's response to infection, increasing susceptibility to infections and promoting growth of tumors, states lead researcher Roberta Pacifici, PhD, with the Instituto Superiore di Sanita in Rome, Italy.

But researchers also say this finding could lead to new treatments for people with autoimmune disorders. Current treatments suppress the immune system -- thereby calming the abnormal immune response that plagues people with the conditions.

Cannabis lowers levels of the inflammation-promoting protein interleukin-2 and raises levels of the anti-inflammatory protein interleukin-10. Both of these findings could be of potential benefit for treating autoimmune disorders one day.

SOURCE: The Journal of the American Medical Association, April 16, 2003.