Concordia researcher investigates how cannabinoids affect the immune system

With the 2018 legalization of marijuana in Canada, cannabis has been a hot topic in recent months.

While the drug has been legal for almost a year, and nearly five million Canadians reported using it in the second quarter of 2019 alone, there is still a gap in our understanding of how it truly affects the immune system.

One Concordian is studying ways the still-controversial plant and its by-products can be used to treat autoimmune disorders.

“My project aims to investigate circadian rhythmicity in healthy T cells, and to understand how cannabinoids may play a role,” says Norhan Mehrez, a second-year psychology master’s student in the Faculty of Arts and Science.

T cells are a subset of white blood cells that play an important role in adaptive immunity by coordinating an immune response among themselves and various other immune cells. They are essential for defending the body against pathogens, but if they are dysregulated, there is a risk of autoimmune disease in susceptible individuals.

Mehrez’s research is co-supervised by Shimon Amir, professor in the Department of Psychology and a researcher with the Center for Studies in Behavioral Neurobiology, and Peter Darlington, associate professor in the Department of Health, Kinesiology and Applied Physiology.

“Two major components of Cannabis sativa, THC and CBD, have been shown to regulate the function of immune cells,” Mehrez explains.

“Cannabis has immunosuppressive properties, which can be detrimental if you’re fighting off an infection but may be useful in cases of autoimmune disorders.”

Cannabinoids and circadian rhythms

An important aspect of T-cell functioning is the time of day, which affects how many circulating T cells we have, with numbers peaking overnight and dropping to their lowest in the afternoon. These 24-hour cycles, known as circadian rhythms, may help provide an optimal immune response to pathogens.

One way T cells maintain these rhythms is through cycling activation of timekeeping genes dubbed “clock genes.”

Mehrez collects blood samples from healthy participants, isolates their T cells and administers different treatments, including drugs that trigger T-cell activation, simulating an immune response in the body.

“I then add different types of cannabinoids, both natural and synthetic, and measure how the immune cells react. This will help hone in on the mechanism by which cannabis might have immunosuppressive properties, and whether these effects are through time-dependent mechanisms.”

Mehrez analyzes her samples every four hours for 36-hour time courses in the laboratory to find out whether circadian rhythms are unaffected, disrupted or protected from the addition of cannabinoids.

Challenges in studying T cells

Mehrez admits the project is not without its challenges and limitations.

“Studying T cells or any immune cell in general can prove to be a difficult task, as immune cells can be affected by a plethora of factors. This includes the participant’s stress levels before the blood draw, their genetic makeup, their diet and more,” Mehrez says.

Additionally, the reactions of T cells to cannabinoids once they are outside the body in the laboratory may not be the exact same as the reaction of T cells in the body when a person consumes cannabinoids.

“Despite these challenges, isolating T cells in the laboratory is a good way to have control over their environment and treatment to understand their basic cellular mechanisms.”

Immune rhythms and autoimmunity

The importance of timekeeping for T cells goes beyond protection against pathogens. In animal models, making the animal sleep deprived or placing it in constant light or dark conditions can disrupt circadian rhythms. These animals tend to have a higher rate of immune problems and worsened outcomes in models of autoimmune diseases linked to T-cell disruption.

In humans, there have been correlational findings that shift workers may be more prone to developing autoimmune illnesses.

“While we know that immune rhythms are important in both health and disease, mechanisms by which these rhythms are maintained and disrupted need to be further investigated,” adds Mehrez.

“Understanding how cannabinoids affect rhythms of the immune system can help bridge our gap in understanding how and why certain cannabinoids are immunosuppressive, for better and for worse.”

Norhan Mehrez’s research is made possible thanks to funding from the Natural Sciences and Engineering Research Council of Canada.

Learn more about the Department of Health, Kinesiology and Applied Physiology and the Department of Psychology.