Comprehensive Effects of CBD on the Human Immune System

For thousands of years, humanity has used cannabis as a therapeutic remedy. Many of the healing properties of cannabis and its extracts were known to ancient civilizations around the world, from the Greeks and early Chinese dynasties to tribal peoples and city-states of the New World. While ancient healers recorded numerous recipes for preparing and using cannabis-based medicines, they lacked the tools to deeply study the mechanisms behind these effects.

In modern times, after nearly a century of global criminalization of the plant, the restrictions have begun to loosen, allowing doctors and scientists to study cannabis properties at the molecular level for the first time. This has enabled humanity to begin understanding how the plant’s medicinal properties work. However, even with advanced technology for analyzing cannabis at the smallest scales, some mechanisms and patterns of cannabinoid function, as well as the human endocannabinoid system, remain a mystery.

This article explores the complex and sometimes contradictory effects of cannabis on the human immune system. Some scientific studies claim that THC and CBD, the main active components of the plant, can suppress immune responses and inflammation in soft tissues, while other research suggests the opposite, showing that these cannabinoids can significantly stimulate the production of white blood cells.

Most medical professionals agree that the ambiguous effects of cannabinoids on biological systems may be due to their interactions with the CB1 and CB2 receptors of the body’s endocannabinoid system. Therefore, this article reviews various studies on how cannabinoids affect the immune system and the conditions that may determine the manifestation of these effects.

How the Human Immune System Works

The human body is constantly under attack from billions of microscopic threats: fungi, bacteria, and viruses surround us daily and can potentially harm our health. To defend itself, the body has an automated defense system—a dense network of receptors and cells that can detect and neutralize threats without harming the body.

The main line of defense is made up of white blood cells, also known as leukocytes or neutrophils. These cells are divided into two subgroups based on their functions: lymphocytes (B and T cells), which directly destroy antigens and remember threats for faster future responses, and phagocytes, which engulf and remove harmful bacteria from the body.

Some readers may be familiar with T cells, as HIV infection disables them, making the body vulnerable even to harmless infections. The body naturally replenishes its supply of protective cells, producing new ones to replace old ones and destroying expired cells to prevent them from becoming cancerous.

Without these cells, the human body would be completely open to attack from viruses and bacteria. Dysfunction in their natural operation can lead to severe diseases like HIV and various forms of cancer.

The Connection Between the Endocannabinoid and Immune Systems

For the immune system to function optimally, the body must maintain homeostasis—a balanced and coordinated operation of all biological systems. Research from the early 1990s showed that cannabinoids affect immune function by interacting with a special class of receptors found in the tissues of every organ. These are the CB1 and CB2 receptors, which regulate the endocannabinoid system.

Normally, these receptors interact with endocannabinoids produced by the body, such as anandamide and 2-AG, which are functional and structural analogs of the plant cannabinoids THC and CBD, respectively.

The endocannabinoid system acts as the body’s main regulatory system. When dysfunction or injury is detected, its receptors signal the brain, which then releases a small amount of endocannabinoids to address the issue. If the system is out of balance, its response may be delayed, worsening injuries or illnesses and causing complications.

Each group of receptors differs in activation, function, and location. CB2 receptors are more widely distributed, mainly at the ends of the peripheral nervous system, and are about 100 times more dense than CB1 receptors, which are concentrated in major organs and the central nervous system.

CB2 receptors trigger anti-inflammatory responses to injuries or infections. If these receptors are suppressed or dysfunctional, the response does not occur, allowing infections to progress. THC and CBD are the main activators of CB1 and CB2, respectively, but each also suppresses the opposite receptor. This may explain the paradoxical effects of cannabis on the immune system, as the interaction of cannabinoids and other plant compounds can dramatically influence the overall effect.

The Effects of Cannabis on the Immune System

Cannabis contains over 400 unique compounds, about 100 of which are cannabinoids. Most of these, except for THC and CBD, are present in only trace amounts in most strains, minimizing their effects. The rest are terpenes, flavonoids, and other plant compounds like chlorophyll.

Despite ongoing research, scientists have mainly studied only two cannabinoids, and their effects on immune mechanisms are not yet fully understood. THC, discovered in the 1960s, is the most studied cannabinoid. Many studies show that THC activates CB2 receptors, producing an anti-inflammatory effect, suggesting it acts as an immunosuppressant. This is supported by its effectiveness in treating autoimmune diseases like Crohn’s disease and multiple sclerosis. CBD, on the other hand, blocks CB2 activity, also suppressing immune responses by reducing cytokine production and T cell activity.

However, some studies have found that certain cannabinoids and their combinations can have an immunomodulatory effect, enhancing rather than suppressing the immune response.

Cannabis and HIV Infection

This immunomodulatory effect was discovered in experiments studying the use of cannabinoids to treat HIV symptoms. These studies mainly focused on the palliative effects of cannabinoids, such as pain relief, improved appetite, and better sleep. However, some researchers noted that THC, in particular, enhanced patients’ ability to resist opportunistic infections.

Early studies in the 2000s concluded that cannabinoids had a noticeable immunosuppressive effect, potentially accelerating HIV progression and increasing the risk of fatal outcomes. However, in 2011, a team from Louisiana State University published research showing immunomodulatory properties of THC. In experiments with monkeys, those given THC before being infected with HIV showed a short-term boost in immune response and resistance to infections.

By 2014, the same team conducted a larger study where monkeys consumed THC daily for 17 months before being infected with SIV (the monkey equivalent of HIV). The results showed increased T cell production and a protective effect on organ tissues, especially the small intestine, which is usually severely affected by the virus.

Similar effects were observed in human volunteers. A study by researchers from Florida and Virginia found that HIV-positive individuals who regularly used cannabis had higher levels of CD4 and CD8 white blood cells compared to non-users. Analysis of 95 patients showed that regular cannabis users generally felt better both physically and psychologically than those using other treatments.

Cannabis and Cancer

Cancer is another major health challenge that remains difficult to treat. Unfortunately, it is even more widespread than HIV. Scientists still do not fully understand what causes cancer, despite detailed knowledge of tumor progression. Some experts believe the risk of cancer is increasing every year, with predictions that half the world’s population may face some form of cancer in their lifetime.

The immune system’s white blood cells are designed to detect and destroy foreign microorganisms and pathogens, but they ignore cancer cells, perceiving them as part of the body. According to Esther Martinez, a cannabinoid researcher at Complutense University in Madrid, cancer cells send a “disarm” signal to white blood cells, causing the immune system to ignore the rapidly growing tumor tissue.

With the immune system’s “approval,” tumors grow even faster. Because of this unique ability, cancer can resist all pharmaceutical drugs and immunomodulators. Currently, the only partially effective treatment is chemotherapy, which uses toxins that damage not only the tumor but also healthy tissues and the entire body. In other words, the treatment can be as dangerous as the disease itself.

For these reasons, the medical community and cancer patients are closely watching research on the use of CBD and THC in cancer therapy. Early trials, led by Martinez and colleagues Manuel Guzman and Cristina Sanchez, suggest that a mixture of cannabinoids may be the first safe substance for healthy tissues that not only slows disease progression but also destroys cancer cells. Cannabinoids also eliminate diseased cells through alternative mechanisms beyond standard apoptosis (cell death).

Another experiment, published in 2014 by Dr. Wai Liu, studied the effects of various cannabinoid mixtures on malignant tumors implanted in rats. The study combined cannabinoids with regular radiation therapy. After a few months, Dr. Liu found that a combination of THC and CBD, along with radiation, helped shrink various tumors, including malignant brain tumors, to minimal sizes without negatively affecting the rats’ overall health or immune system function.

Despite these findings and many personal reports of successful cannabinoid use in cancer therapy, most medical institutions still refuse to conduct such trials on human volunteers, citing the potential for immunosuppressive effects. Dr. Liu also observed a dual effect of cannabinoids on immune system activity, noting that while cannabinoids killed cancer cells, they also accelerated the death of lymphocytes, possibly causing immunosuppression. He suggests that this temporary suppression may be one way cannabinoids, through the endocannabinoid system, protect the body from pathogens by reducing inflammation and oxidative stress, after which the immune system recovers and sends new neutrophils to eliminate weakened pathogens.

Cannabinoid Immunotherapy for Cancer

Despite these private trials and thousands of self-treatment stories, science cannot fully endorse cannabinoids for treating cancer, HIV, or other immune-related diseases due to the lack of large-scale clinical studies. The only such preclinical trial, conducted at Rambam Medical Center in Haifa, produced mixed results regarding the effects of cannabinoids on the immune system in cancer patients.

In this study, patients with various types and stages of cancer took different combinations and concentrations of THC and CBD, along with a new, powerful immunostimulant called Nivolumab, designed to enhance traditional cancer treatments. The pharmaceutical drug proved more effective than many cannabinoid mixtures or extracts, and its combination with medical cannabis or extracts reduced its overall effect by about 50%. However, in high concentrations, isolated or mixed THC extracts had a more pronounced and lasting immunomodulatory effect than low doses. Overall, cannabinoids slightly improved patients’ psychological well-being but did not significantly affect survival or recovery rates.

Meanwhile, many individual reports from California claim that combining THC and CBD in moderate, balanced concentrations with standard treatments (chemotherapy, immunostimulants, and radiation) quickly helps reduce and put even the most dangerous tumors into remission. However, as with other such reports, this information is not yet formally confirmed by scientists or doctors.

Dr. Mariano Garcia de Palau, a specialist in therapeutic cannabis and a member of the Spanish Association for the Study of Cannabinoid Therapeutic Effects, agrees with Dr. Liu’s view of the dual properties of cannabinoids in modulating immune response. He believes that both THC and CBD have complex effects on the human immune system, determined by as-yet-unknown endogenous factors.

“Based on all the information we have from private research teams and individual doctors and patients, cannabis has a noticeable suppressive effect on the immune system only when it is overactive,” Dr. Garcia de Palau suggests. “If the endocannabinoid system detects low immune activity, cannabinoids stimulate the production and activity of white blood cells to restore normal function. The modulatory effect of cannabis is that it adjusts the immune response to work in harmony with other biological systems, depending on their state and function.”

So, should cannabis or its extracts be used to treat cancer, HIV, or other diseases affecting the immune system? Considering all factors and possible risks, one thing is clear: such therapy should be conducted under the supervision of a doctor experienced in cannabis medicine. While thousands of positive online reviews may contain some truth, the lack of formal evidence means that self-treatment experiments should be undertaken at one’s own risk.

Original author: Mary Biles