Researchers at Georgetown University Medical Center chose the start of yet another sun-starved winter to publish a study showing that exposure to blue light and ultraviolet light increases the movement of T cells, a key part of the immune system. Sunlight, therefore, could be an immune booster.
"There's some connection between sunlight and human health, autoimmunity or even cancer," says Gerard Ahern, an associate professor of pharmacology and physiology at Georgetown and the study's senior author. Researchers have long known that sunlight stimulates Vitamin D production in the skin; Ahern and his colleagues have identified another potentially beneficial effect of sunlight that is independent of Vitamin D.
The researchers isolated T cells from human blood and mice and grew them in dishes in the laboratory. When they shined either UV or blue light on the cells, the cells became activated and moved more quickly. Additional tests helped the researchers determine that five or 10 minutes in the sun is all that's needed to get this effect. Another series of experiments helped demonstrate that light stimulated the production of hydrogen peroxide, and that's what made the T cells move faster.
Although both UV and blue light increased the cells' movement, researchers focused on the potential benefits of blue light for two reasons: UV light is known to cause cancer, and it reaches only the outermost layer of skin, the epidermis. Blue light can reach deeper to the second layer, the dermis, where most of the skin's T cells are located. If light could spur these immune cells to get to an infection more quickly, it could be leveraged via lamps to boost immunity and help treat skin diseases or even cancer.
"To my knowledge, this is really the first study that has shown an impact [of light] on this type of immune cell," says Dr. Matthew Galsky, an oncologist and professor at Mount Sinai Hospital's Icahn School of Medicine. "One could make the leap—although it would require much more investigation—that exposure to light could impact the movement of immune cells in our body, which might impact how our body reacts to things like infections [or] cancer."
Galsky can imagine blue light as a complement to immunotherapeutic approaches to treating cancer. But don't call him just yet. This is an observation made in the laboratory in petri dishes, he says, and requires extensive validation before we understand whether it can be useful in the clinical realm. Best advice: Hold off on therapeutic tanning.
