By Luke Sumpter

We wouldn’t last very long without our immune system. We’re constantly surrounded by bacteria, fungi, and viruses that would jump at the chance to access the resources within our cells. Our immune system comprises numerous organs, cell types, and proteins that provide several lines of defence against these external threats. However, they aren’t always enough to stamp out an infection before it takes hold. We all encounter colds, flu, and other infectious illnesses every now and then, but the genius of our immune system ensures that we’re better equipped to deal with them next time.

In order to reduce the likelihood of getting sick, many people look for ways to boost or modify their immune system through nutrition, exercise, lifestyle adjustments, and supplements. While science supports some of these strategies, others are treated with more scepticism. But where does cannabis fall on this spectrum? Can the herb help to bolster our cellular defences and prevent or minimise infections? Or does it make matters worse? Below, we explore these questions and more.

How the Immune System Works

Before we get into how cannabis could impact immunity, let’s quickly cover how the immune system works. Our physiological defences feature two primary categories: innate immunity and adaptive immunity.

We are all born with an innate (or general) immune system that serves as the first line of defence against pathogens entering the body. It comprises barriers such as the skin and the mucous membranes (the inner lining of the nose, mouth, lungs, and other organs and cavities) that physically prevent the movement of pesky germs.

These biological walls also harness enzymes, acids, and mucus to discourage the formation of bacteria and viruses. Scavenger cells known as phagocytes also make up the innate immune system. “Phago” stems from the Greek “phagein”, which means “to consume”. Phagocytes live up to their name by enveloping and “eating” intruding pathogens.

Whereas our innate immunity uses a scattershot and unselective strategy to destroy invaders, our adaptive (or acquired) immunity works much more specifically to tackle intruders. If our innate defences fail, the adaptive immune system arrives as backup and begins to identify the pathogen and create specific antibodies designed to kill it.

Below are the two main players involved in this process:

T lymphocytes
These cells activate other immune cells, detect and destroy cells affected by viruses, and form “memories” of pathogens to ensure future immunity.
B lymphocytes
Forged in the bone marrow, these cells transform into plasma cells and churn out large numbers of antibodies—compounds made from sugars and proteins that are specifically designed to attach to and destroy an antigen.

Cannabis, the Endocannabinoid System, and Immunity

The immune system doesn't work in isolation—nothing in the body does. If you know a thing or two about cannabis, you’ve probably heard of the endocannabinoid system (ECS). Researchers came across the components of this system while studying the effects of cannabis on the body. Eventually, they figured out that its components show up all over the body, from the brain and bones to the skin, digestive system, and immune system. They deemed the ECS the “universal regulator” of the human body, as it helps to keep everything in a state of balance, otherwise known as homeostasis.

The classical ECS features two receptors (CB1 and CB2), endocannabinoids that act as signalling molecules (anandamide and 2-AG), and enzymes that build and break down endocannabinoids. These components are also found throughout the immune system, where they help to control immune function, drive homeostasis, and modulate the immune system. A wide array of immune cells feature CB1 and CB2 receptors, including B cells, natural killer cells, monocytes, and CD8 and CD4 lymphocytes. Endocannabinoids bind to these sites and help to regulate processes such as the inflammatory response[1].

Cannabis, the Endocannabinoid System, and Immunity

Cannabis and the Immune System

The intimate link between the ECS and the immune system opens up the possibility of cannabis working as a modulating agent of our physiological defences. You see, endocannabinoids (those found in the body) and phytocannabinoids (those found in plants) share a similar structure. This means that external cannabinoids, including THC and CBD, are potentially able to bind to ECS receptors, influence enzyme activity, and generally mimic endocannabinoids. As our endocannabinoids hold significant influence over our immune system, plant cannabinoids might serve as a way of “hacking” the ECS when it comes to immunity.

  • Autoimmune Disorders

Sometimes the immune system goes haywire. In the case of autoimmune diseases, the cells that are supposed to protect us from outside invaders start to turn on our own bodily tissues; they mistake joints, skin, and nerve cells for aggressive bacteria and viruses. This self-inflicted damage leads to inflammatory cascades that result in symptoms such as fatigue, achy muscles, fever, hair loss, and rashes. Common autoimmune conditions include rheumatoid arthritis, psoriasis, and multiple sclerosis.

Early research has pitched cannabinoids against inflammation involved in autoimmune disease progression. Animal and cell studies also suggest that cannabis could exert an immunosuppressive effect[2].

  • Risk of Viral Infection and Immunosuppression

If cannabis interacts with the immune system in a way that suppresses it, could it give viruses and other infectious pathogens an upper hand? It’s a possibility. Because of this effect, cannabis could predispose long-term and heavy users to an increased risk[3] of acquiring and transmitting infections, and impaired immune function in general.

Even more worrisome, limited research also suggests that long-term cannabis use could trigger myeloid-derived suppressor cells (MDSCs), which suppress the immune system and may increase the odds of cancer[4]. However, despite their effects on the immune system, ongoing studies are exploring some cannabis compounds for their impact on pathogenic viruses and bacteria.

  • Neurodegenerative Conditions

The autoimmune disease multiple sclerosis is characterised by neurodegeneration. Immune cells launch an inflammatory attack against the central nervous system. During this process, the cells develop a particular affinity for myelin—the protective and insulating coating that encases nerve cells. Over time, this assault damages the myelin and the nerve itself, which can cause problems with nervous system firing. Ongoing studies are looking at a potential neuroprotective effect[5] of the CB1 receptor and compounds that bind to this site.

Cannabis and the Immune System
  • Coronavirus

SARS-CoV-2, which causes the disease COVID-19, changed the world. Despite the worldwide vaccine rollout, cases continue to rage in many regions, and researchers are still on the hunt for therapeutics.

Some research teams have decided to probe cannabis for potentially useful molecules. Although certain cannabinoids may dial down the immune response, others are being explored for their direct effect on virus particles. Additionally, the deadlier end stages of COVID-19 are driven by inflammatory storms.

Currently, researchers from Portugal are testing blends of CBD and terpenes[6] against SARS-CoV-2 infectivity. Other researchers are testing[7] the cannabinoid acids cannabigerolic acid (CBGA) and cannabidiolic acid (CBDA) against SARS-CoV-2 entry into host cells.

Can Smoking Weed Weaken the Immune System?

Research efforts continue to explore the potential of cannabis compounds in addressing autoimmune issues. However, as cannabis is thought to "dial down" immune system activity, does this mean smoking weed can weaken the immune system under normal circumstances? A review[8] on the topic, published in the journal Viruses, states the need for more research in this area. Based on current data, the paper argues that cannabis use likely impairs immune function to some degree, and may predispose users to an increased risk of certain viral infections. Adding to this, the act of smoking introduces carcinogens and toxins into the body that can throw the immune system out of balance[9] and increase the odds of several immune disorders.

Despite these findings, other research continues to determine the antibacterial and antiviral properties of cannabis constituents. Instead of boosting the immune system, certain cannabis compounds have shown the ability to directly impact bacteria[10] and viruses[11] in test tube conditions. Future studies are needed to see if these effects are replicable in humans.

CBD and the Immune System

So, where does cannabidiol stand when it comes to weed and the immune system? Does CBD help the immune response? Or does it play a role in lowering its activity? Unlike THC, CBD doesn’t have much affinity for the primary receptors of the endocannabinoid system. However, preliminary research shows that the molecule might elevate endocannabinoid levels. Little evidence claims that CBD works to boost the immune system, but ongoing studies are looking to determine the immunosuppressive properties[12] of the cannabinoid. Thorough human trials are needed to determine if CBD can produce notable effects in patients with autoimmune conditions.

Is Cannabis Good or Bad for the Immune System?

We don’t have enough data to provide a confident answer to that question. Some evidence suggests that the herb has immunosuppressive properties that could be beneficial; however, if this is true, it could also potentially cause problems in those with compromised immune systems, as well as healthy individuals that use the herb often. The bottom line: we need more human trials to ascertain a clear-cut answer.

External Resources:
  1. Endocannabinoids and immune regulation - PMC
  2. Cannabinoids and the immune system: an overview - PubMed
  3. Cannabis and Autoimmunity: Possible Mechanisms of Action - PMC
  4. The Link between Cannabis Use, Immune System, and Viral Infections - PMC
  5. Cannabidiol for neurodegenerative disorders: important new clinical applications for this phytocannabinoid? - PMC
  6. Cannabinoids and autoimmune diseases: A systematic review - PubMed
  7. About cannabis and MS | MS Society
  8. Functional role of cannabinoid receptors in urinary bladder - PMC
  9. Relationship Between Marijuana Use and Overactive Bladder (OAB)
  10. The effect of cannabis on urge incontinence in patients with multiple sclerosis: a multicentre, randomised placebo-controlled trial (CAMS-LUTS) - PubMed
  11. The Safety and Efficacy of Marijuana in Persons Living with HIV - PubMed
  12. Cells | Free Full-Text | Cannabinoids Reduce Extracellular Vesicle Release from HIV-1 Infected Myeloid Cells and Inhibit Viral Transcription
This content is for educational purposes only. The information provided is derived from research gathered from external sources.

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