Immune Cells’ Reaction to Sunlight Studied

U.S. medical scientists say they’ve discovered immune cells travel to protect the outer layers of the skin in response to sunlight-induced vitamin D.

Eugene Butcher and colleagues at the Stanford University School of Medicine say the immune cells express enzymes that convert an inactive form of vitamin D — which is synthesized by skin cells upon sun exposure — to an active form that triggers expression of certain homing receptors on the surface of effector T cells.

Those receptors, say the researchers, can draw T cells to the skin’s surface where they participate in immune surveillance and maintain barrier function.

The study suggests brief periods in the sun to generate the precursor form of active vitamin D might be beneficial by eliciting immune cells to skin tissues where they can ward off potential opportunistic pathogens and help repair ultraviolet light-induced damage.

The research is detailed in the March issue of Nature Immunology.