"The bottom line is you cannot routinely smoke marijuana without it affecting your immune system," said Thomas Klein, PhD, professor of medical microbiology and immunology at USF. "However, because of the complexity of the immune system, we can't say yet whether the effect we've observed in humans is good or bad."

A study by USF and UCLA is the first to show that healthy humans who smoke marijuana appear to alter the expression of marijuana receptors, or molecules, on immune cells in their blood. The findings were reported in the June issue of the Journal of Neuroimmunology.

Pot's influence on the immune system continues to be hotly debated. While more human studies are needed, overwhelming evidence from animal studies indicates that marijuana and its psychoactive compounds, known as cannabinoids, suppress immune function and inflammation.

"This suggests marijuana or cannabinoids might benefit someone with chronic inflammatory disease, but not someone who has a chronic infectious disease such as HIV infection," said Dr. Klein, lead investigator of the study.

The USF/UCLA group is one of few in the world conducting studies to define the role of cannabinoid receptors in regulating immunity in both drug abusers and nonusers.

If the results in animals hold true in humans, their work might lead to the development of safe and effective cannabinoid drugs for certain diseases, Dr. Klein said. "If the cannabinoids in marijuana are effective immune suppressors, this property might be harnessed to treat patients with overly aggressive immune responses or inflammatory diseases like multiple sclerosis and rheumatoid arthri
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Contact: Anne DeLotto Baier
abaier@hsc.usf.edu
813-974-3300
University of South Florida Health
27-Aug-2002