Smoking Pot Alters More Than Mood ‹ Human Immune System Affected, USF/UCLA Study Finds

[Guest guest]

Source:   University Of South Florida Health Sciences Center

(http://hsc.usf.edu/)

Date:   Posted 8/28/2002

Smoking Pot Alters More Than Mood ‹ Human Immune System Affected, USF/UCLA

Study Finds

Tampa, FL (Aug. 27 2002) -- Marijuana may alter immune function in people --

but the jury is still out on whether it hurts or helps the body's ability to

fight infection or other diseases, report researchers at the University of

South Florida College of Medicine and the UCLA School of Medicine in Los

Angeles. " The bottom line is you cannot routinely smoke marijuana without it

affecting your immune system, " said 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 arthritis. "

Receptors that react to delta-9 tetrahydrocannabinol or THC, the compound in

marijuana that produces a high, have been found in tissues throughout the

body and in the brain. A naturally circulating THC-like substance called

anandamide also binds to and activates these marijuana, or cannabinoid,

receptors, indicating that the body's own cannabinoid system plays a

physiological role in normal immunity as well as defining moods, Dr. Klein

said.

In the USF/UCLA study, researchers analyzed blood samples from 56 healthy

volunteers -- including 10 chronic marijuana smokers, ages 22 to 46,

participating in lung and immune function studies at UCLA. The marijuana

smokers denied use of any other drugs, and the nonsmokers denied all illegal

drug use. Because no accurate way yet exists to directly study the

expression of cannabinoid receptors on immune cells, the researchers looked

at the genetic material (messenger RNA) that is the direct predecessor, or

precursor, of the receptor.

They found that the baseline genetic expression of precursor RNA was

consistent across all age, gender and ethnic groups. But, the peripheral

blood cells from the marijuana users expressed significantly higher levels

of cannabinoid receptor messenger RNA than blood cells from non-users. The

levels increased regardless of the amount of marijuana use, although all

users in the study had a history of smoking pot several times or more a

week.