CBD and THC May Alter How Human Immune Cells Develop

Cannabis research has traditionally focused on how cannabinoids affect the brain, pain, inflammation, and the body’s endocannabinoid system. However, scientists are increasingly discovering that CBD and THC may influence far more than previously believed, including the earliest stages of immune system development.

A 2026 study¹ published in Toxicology suggests that both CBD and THC can alter how human blood-forming stem cells develop into different types of immune cells under laboratory conditions. While the research does not study human immune development in real life, they reveal a previously unexplored aspect of cannabinoid biology and raise important questions about cannabis exposure during pregnancy, early development, and other periods when the immune system is still forming. Let’s dive into the research and what it means for the future prenatal cannabis research.

The Immune System Begins With Stem Cells

Every blood cell in the body starts from a small population of cells known as hematopoietic stem and progenitor cells. These cells reside primarily in bone marrow and serve as the foundation for the entire blood and immune system. As these stem cells mature, they gradually specialize into many different cell types, including:

• B cells that produce antibodies
• Monocytes that help engulf bacteria and damaged cells
• Dendritic cells that activate immune responses
• Megakaryocytes that eventually produce platelets responsible for blood clotting

Normally, this developmental process is tightly regulated. Small changes during these early stages can potentially influence how the immune system functions later in life. Until now, relatively little was known about whether cannabinoids could affect this process directly.

Cannabis and Early Immune Development

To investigate how cannabinoids effect the developing immune system, researchers grew human hematopoietic stem and progenitor cells in the laboratory for 28 days while exposing them to varying concentrations of CBD and THC. Because this was an in vitro study, the cells were grown outside the human body in carefully controlled laboratory conditions. This allowed researchers to observe how the cannabinoids influenced immune cell development without the many variables present in living people.

Due to the nature of the study, the findings should not automatically be interpreted as evidence that cannabis products produce the same effects in humans. Instead, the study provides an important first look at what may happen when developing immune cells encounter cannabinoids during their earliest stages of growth.

CBD and THC Accelerated Stem Cell Differentiation

One of the most striking findings involved cells carrying a marker known as CD34, which identifies immature blood-forming stem cells before they develop into specialized immune cells. Researchers observed that both CBD and THC reduced the number of CD34-positive cells over time.

Rather than indicating that the cells were dying, the results suggest the stem cells may have been differentiating, or maturing into downstream immune cells, more quickly than expected. In other words, CBD and THC appeared to influence the pace at which these foundational stem cells began choosing their future identities. However, exactly what this accelerated development means for long-term immune health remains unknown.

A Strong Shift Toward B Cells

Perhaps the most notable discovery was a significant increase in early B-cell populations. B cells play an essential role in adaptive immunity by producing antibodies that recognize viruses, bacteria, and other foreign invaders. They also help create long-term immune memory following infections and vaccinations.

Researchers found that both CBD and THC consistently increased the proportion of developing CD19-positive B cells throughout the experiment. This suggests the cannabinoids may encourage developing stem cells to commit to the B-cell lineage more readily than they otherwise would.

While that finding is scientifically fascinating, it should not be interpreted as either beneficial or harmful. The immune system depends on maintaining a careful balance among many different cell types and changing that balance could have complex consequences that remain unknown.

Other Immune Cells Were Also Affected

The research found that the effects were not just limited to B cells. Researchers also observed changes involving developing monocytes, which are immune cells that circulate through the bloodstream before becoming macrophages or certain types of dendritic cells.

Higher cannabinoid concentrations produced increases in developing monocyte populations at several time points. Researchers also found increases in megakaryocyte progenitors during later stages of development. Megakaryocytes are large bone marrow cells responsible for producing platelets, which help blood clot following injury. These findings suggest CBD and THC may influence multiple branches of blood cell development rather than affecting only a single immune pathway.

Study context: Human umbilical-cord blood stem and progenitor cells were exposed once, on day 0, to CBD or THC concentrations of 1, 3, 5, or 10 µM and followed for 28 days. These were laboratory cell-culture findings and do not establish equivalent effects in humans.

CBD Enhanced One Immune Function

The researchers went a step further by testing whether the newly developed immune cells behaved differently. They examined phagocytosis, a process in which immune cells engulf bacteria, dead tissue, and other unwanted material. Monocytes and a subset of dendritic cells that developed in the presence of CBD demonstrated greater phagocytic capacity than untreated cells.

This finding indicates that cannabinoids may influence not only how immune cells develop but also how effectively certain immune cells perform specific tasks once they have formed. However, laboratory measurements of a single immune function do not necessarily predict overall immune performance in people, as the immune system is extraordinarily complex, with countless interacting pathways that cannot be fully replicated in cell culture.

THC’s Effects May Involve Unexpected Pathways

Cannabinoids often exert their biological effects through cannabinoid receptors, particularly CB1 and CB2. CB2 receptors are especially abundant throughout the immune system, making them an obvious suspect for mediating THC’s effects. Surprisingly, researchers found that THC’s influence on developing immune cells was not driven by the CB2 receptor. That unexpected result suggests other signaling pathways may be involved in regulating immune cell development.

Understanding those mechanisms will require additional research and could reshape scientists’ understanding of how cannabinoids interact with the immune system beyond the traditional cannabinoid receptors.

What Does This Mean for Pregnancy?

Although the study was not designed to examine pregnancy directly, its findings naturally raise questions about cannabinoid exposure during fetal development. During pregnancy, a baby’s blood-forming stem cells are actively building the immune system that will support health throughout life. If cannabinoids influence those early developmental decisions, scientists need to better understand whether similar effects occur in living organisms and, if so, whether they have meaningful health consequences.

However, the current study cannot answer those questions because it examined isolated human cells in a laboratory rather than pregnant individuals or developing fetuses. Still, the authors say the findings support continued investigation into the safety of cannabis and cannabinoid use during critical developmental periods.

Final Thoughts

One of the most important aspects of this study is that it opens an entirely new area of cannabinoid research. For decades, scientists have recognized that CBD and THC can influence mature immune cells by altering inflammation and immune signaling. This research suggests cannabinoids may also affect immune cells much earlier while they are still deciding what type of cell they will become, representing a significant shift in thinking.

At the same time, the study should be interpreted carefully. The experiments were performed in cultured human cells using laboratory conditions that do not fully replicate the complexity of the human body. Additional animal studies, clinical research, and mechanistic investigations will be needed before scientists can determine whether these developmental changes occur in real-world settings or what they might mean for human health.

For now, the findings do not demonstrate that CBD or THC harms immune development in people. Instead, they reveal that these cannabinoids are biologically active during one of the earliest stages of blood and immune cell formation, a discovery that broadens our understanding of cannabis biology and points researchers toward important new questions that have yet to be answered.

Reference:

^{1. D M Isha Olive Khan, Robert B. Crawford, Norbert E. Kaminski, Cannabidiol and Δ9-tetrahydrocannabinol alter human hematopoiesis by enhancing B cell lineage commitment, Toxicology, Volume 526, 2026, 154537, ISSN 0300-483X, https://doi.org/10.1016/j.tox.2026.154537}