Natural Killer T Cells Are Responsible for Skin Allergies, Yale Researchers Find

Yale researchers have found that natural killer T cells (NKT), a combination of T lymphocytes and natural killer (NK) cells, are involved in the formation of skin allergies such as poison ivy and contact sensitivity to chemicals and metals like nickel in jewelry.

“We have shown for the first time that NKT cells are required in contact sensitivity skin allergies,” said principal investigator Philip Askenase, M.D., professor of internal medicine, pathology and section chief of allergy and clinical immunology at Yale School of Medicine. “We previously demonstrated the role of NKT cells in asthma and we believe they are implicated in many allergic disorders, and also some autoimmune diseases and cancers.”

Allergies are abnormal or hypersensitive responses of the immune system to relatively harmless environmental antigens. Some people are genetically predisposed to hypersensitivity. When they are exposed to skin allergens like poison ivy, the initial exposure leads to a state of hypersensitivity; the body produces an exaggerated reaction the next time skin comes into contact with the allergen.

The resulting skin inflammation and severe itch are caused by over-reaction of effector T cells, white blood cells that migrate to the skin when re-exposed to an allergen. In some people, initial contact with an allergen such as a poison ivy plant, causes a danger alert and NKT cells are activated rapidly within minutes. There are usually no outer symptoms after the first contact with poison ivy, but this initial contact leads via the NKT cells to a complex process that sets the stage for a hypersensitive response from subsequent contact.

“The NKT cells are ‘alerting the troops’ in anticipation of another contact with the allergen,” said Askenase. “When this occurs the effector T cells move into the affected tissue to respond. This may cause damage to the surrounding tissue.”

“Interfering with the activity of the NKT cells may lead to prevention or better treatment of skin allergies,” Askenase added. “The reaction also may underlie what happens in transplant patients who reject their organs, and has implications for autoimmune diseases and protection from cancers.”

Other authors on the study included Atsuko Itakura, Moe Akahira-Azuma, and Regis A. Campos, Yale; and Marian Szczepanik, Jagiellonian University College of Medicine, Krakov, Poland; Stephanie Sidobre and Mitchell Kronenberg, La Jolla Institute for Allergy and Immunology.

Citation: Journal of Experimental Medicine, Vol. 198, No. 12, Dec. 15, 2003

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Karen N. Peart: karen.peart@yale.edu, 203-432-1326