The human immune system can be one of our biggest assets or one of our greatest foes. The immune system protects us against foreign invaders like viruses and bacteria. It is essential for helping us maintain immunity over a lifetime, whether from immunizations or previous infections. We could not live without our immune systems.
On the other hand, the human immune system is the cause of numerous diseases. Autoimmune diseases like multiple sclerosis, ulcerative colitis, systemic lupus erythematosus, and Crohn’s disease are caused by an immune system that mistakenly attacks our own tissue. Organ and bone marrow transplants fail because the body’s immune system rejects the transplant. When the immune system is functioning normally, it is life-sustaining; however, when the immune system falters, it can cause serious disease, suffering, and even death.
Compared to other diseases, the treatments for autoimmune diseases and other diseases that involve the immune system are limited. Doctors can prescribe steroids to knock down the immune response. These powerful drugs can control disease flareups, but they aren’t a cure. Moreover, steroids cause terrible side effects when taken long-term.
While there have been some recent developments in the treatment of certain autoimmune diseases (e.g. disease-modifying drugs for inflammatory bowel disease), medications are still limited. That is why scientists are actively studying the immune-modulating power of mesenchymal stem cells.
Mesenchymal stem cells exert a number of beneficial effects on the cells of the immune system. Mesenchymal stem cells can suppress T-cells, B-cells, dendritic cells, and natural killer cells (cells that participate in autoimmune diseases). Likewise, mesenchymal stem cells induce and affect the action of regulatory T-cells. This can help fine-tune the immune system, potentially shifting the balance from harmful to helpful immune system function.
Mesenchymal stem cells have been shown to be effective in various Phase I and Phase II clinical trials to treat multiple sclerosis, Crohn’s disease, lupus, ulcerative colitis, and even diabetes. While the clinical trials are often small—15-40 patients—the effects are impressive. Furthermore, treatment with mesenchymal stem cells is consistently safe; in study after study, the risk of serious adverse events is vanishingly small.
As with most fields of medicine, these clinical trials will need to be replicated in larger, Phase III trials. That being said, some large trials have already been conducted with favorable results. Perhaps the best example of a large trial testing the effect of mesenchymal stem cells on immune system function is in the field of transplantation medicine. The prestigious Journal of the American Medical Association (JAMA) published a clinical trial of 159 patients undergoing kidney transplants. Stem cell treatment reduced the incidence of kidney rejection, decreased the risk of opportunistic infection, and was associated with better kidney function 1 year after treatment.
The results from dozens of clinical trials suggest mesenchymal stem cells are powerful modulators of immune cell function and have the potential to one day be tools to treat diseases caused by the immune system. We anxiously await further results from large, Phase III trials.
Reference: Gao, F., et al. (2016). Mesenchymal stem cells and immunomodulation: current status and future prospects. Cell Death & Disease. 2016, Jan; 7(1): e2062.