Since the 90s, a pill form of marijuana has been prescribed to treat appetite and weight loss in HIV/AIDS. But new findings suggest marijuana may even help combat the disease.

Published last week in the journal AIDS Research and Human Retroviruses, researchers at Louisiana State University showed that daily doses of THC, marijuana’s main ingredient, have a number of beneficial effects in animal models of HIV.

In particular, THC given to monkeys over a 17-month period decreased damage to immune tissue of the gut, an important site of HIV infection. The team also found evidence that THC could do this by acting at the gene level.

“It adds to the picture and it builds a little bit more information around the potential mechanisms that might be playing a role in the modulation of the infection,” says Dr. Patricia Molina, head of the school’s Department of Physiology and lead author of the study.

HIV spreads by infecting and ultimately killing immune cells. However, the researchers observed higher levels of healthy immune cells in animals that received THC – something they noticed in a previous study as well.

In 2011, Dr. Molina and her colleagues found that monkeys treated with THC had lower levels of viral infection and better survival rates. They also experienced a spike in immune cells and less weight loss from the disease.

The results were not what her team would’ve predicted, Dr. Molina explains.

“When we started the study, we thought it was going to increase viral load, we thought it was going to decrease lymphocyte counts much more dramatically, and we did not see that. If anything, it looks like there might be some beneficial immunomodulation, particularly at the early stages of infection.”

Many have been skeptical of the use of marijuana in HIV/AIDS patients, since marijuana compounds are known to inhibit activity of the immune system.

But studies have shown that THC does not have a detrimental effect on viral load or immune cells, Dr. Molina says.

Now, researchers are trying to understand why marijuana might help, and develop new treatments that are more specific to its mechanisms.

“I think that there’s a lot of interest in trying to understand the specific receptor-mediated events that result from marijuana. And particularly, to focus on the CB2 receptor.”

Marijuana’s effect on the immune system is mostly due to its action on CB2 receptors, one of the two receptors that THC binds to. On the other hand, CB1 receptors are responsible for the high.

“There’s quite a bit of interest in trying to understand whether what we see as a immunomodulatory effect is mediated exclusively by the CB2 receptor,” Dr. Molina continues. “And if so, could that potentially lead to the development of agonists specific to the receptor that could have the same beneficial effects.”

A study published in 2013 by a Harvard University team found that CB2 activation may also prevent HIV from damaging the brain.

The study received funding from the National Institutes of Health (NIH) and the National Institute on Drug Abuse (NIDA)