Chemical compounds found in skin creams and other personal care products can cause an allergic reaction in the skin, a common condition known as allergic contact dermatitis (ACD). While ACD is on the rise, particularly in industrialized countries, exactly how personal care chemical compounds trigger a reaction remains unknown. Most allergic reactions involving T cells are attributed to proteins or peptide antigens that trigger the immune system. But chemical compounds found in personal care products are different kinds of molecules that were not thought to be able to directly elicit a reaction by T cells. Investigators from Brigham and Women’s Hospital, Columbia University and Monash University have uncovered a new molecular mechanism by which common components of consumer products can trigger an immune response, highlighting a specific molecular connection that may explain the mystery behind these cases of ACD. The team’s findings are published in Science Immunology.
“What we present here is a molecular missing link,” said co-senior author D. Branch Moody, MD, a principal investigator and physician in the Brigham’s Division of Rheumatology, Inflammation and Immunity. “We questioned the prevailing paradigm that T cell-mediated allergic reaction is only triggered when T cells respond to proteins or peptide antigens. We find a mechanism through which fragrance can initiate a T cell response through a protein called CD1a.”
For many substances, such as those found in soaps, cosmetics, fragrances, jewelry and plants, it is unclear how a reaction by T cells is triggered. Chemical compounds found in these products were thought to be too small and of the wrong chemical structure to be detected directly by T cells, which are the immune cells that set off ACD.
