You'll hear a lot about stem cells when learning about cord blood banking, but you may also come across the term Tregs, too. While a Treg may not be able to do all the things that a cord blood stem cell can do, it does offer distinct opportunities in regenerative medicine, especially diseases such as diabetes, rheumatoid arthritis and multiple sclerosis. Just like cord blood stem cells, Tregs are found in the umbilical cord after birth and are part of what is collected when cord blood stem cells are isolated, extracted and preserved. Let's take a look at these cells and see how their cryo-preservation could be useful in regenerative medicine.
What are Tregs?
T cells are also captured in cord blood banking
Regulatory T cells, or Tregs (pronounced tee-regs), are a main regulator of the immune system. Where T helper (Th) cells effect an immune response and cytotoxic T cells (Tc) destroy infected or abnormal cells, Tregs suppress unwarranted or harming activities of the immune system. Metaphorically, the Th cells are like the dispatch office that calls the police (Tc cells) into action, and the Tregs are the dispatcher’s supervisor regulating how the dispatcher responds.
What are tTregs?
The T in Tregs stands for the thymus because this is where it matures. The thymus is a lymphoid located above the heart. It’s since been found that Tregs can be formed in other areas of the body or in cell cultures. To distinguish between Tregs from the thymus and Tregs from other places, the thymic-derived T cells are called tTregs (pronounced Tee-Tee-Regs). A little redundant, but such is often the nomenclature of science.
Why are Tregs important?
Tregs help keep your immune system from becoming too good at what it does. It tells the immune to stop when any sort of infection has been properly extinguished, and it helps prevent your immune system from attacking your own cells, something known as an autoimmune response. If Treg cells are limited in number or deficient in some way, it can cause an autoimmune disease. Some well-known autoimmune diseases include type I diabetes and multiple sclerosis. Diabetes is when the body destroys its own insulin-producing beta cells, located in the pancreas. Multiple sclerosis is when a person’s own immune system attacks myelin, a fatty coating that covers and protects nerves of the spine and brain.
Graft-versus-host disease (GvHD) is a type of autoimmune response that is a large concern for people who have undergone transplants or engraftments, such as when someone is infused with stem cells from an unrelated person. Acute graft-versus-host disease occurs in 40 percent of unrelated transplants and involves damage to the skin, upper gastrointestinal tract and liver. Chronic graft-versus-host disease occurs in 70 percent of unrelated transplants and is characterized by damage to the nails, eyes, mouth, lungs, kidneys, heart, and gastrointestinal tract. GvHD can also be deadly.
The introduction of Treg cells have proven effective against a GvHD response, but Tregs are rare, they do not expansively proliferate, and a high dose may be needed for transplantation. While, up until now, science had yet to establish a way to isolate and expand the necessary number of Tregs from umbilical cord blood, this all is changing.
Tregs and cord blood
Tregs are part of what is captured during cord blood processing, and scientists have recently found a way to expand cord blood–derived tTreg cells. In February 2017, researchers at the University of Florida Health used microbeads to culture 1.26 billion tTreg cells from a harvest of 250,000–500,000 umbilical cord tTregs. Researchers there saw this accomplishment as a step toward stopping type I diabetes. Scientist also recently completed a first-in-human clinical trial using in vitro (outside the body) expanded umbilical cord blood–derived tTregs in patients to prevent graft-versus-host disease.
As cord blood is better than other sources of stem cells, the naïvety of cord blood–derived Tregs is preferred over Tregs from other sources. With the ability to greatly expand these Treg cells, researchers may be on a better path to preventing graft-versus-host disease in stem cell transplantations and ameliorating the effects of autoimmune diseases such as diabetes, rheumatoid arthritis and multiple sclerosis.