The new research is the first to investigate long-term reactions by mast cells to poison oak and sun exposure. His team exposed the ears of mice to either cycles of ultraviolet radiation or urushiol, the irritating oil of poison oak. About a week later, mice genetically lacking mast cells showed much more inflammation than normal mice, and developed skin ulcers. Injections of mast cells helped reduce the ear swelling and prevent the ulceration. "All you have to do to cure the mice of this problem is put the mast cells back in," Galli said.
The discovery originated from an unintended observation by Michelle Grimbaldeston, PhD, first author and postdoctoral scholar in pathology. While similar studies have stopped following mouse reactions past the first 48 hours, she kept records for two weeks. "Just by chance I looked a bit farther along," said Grimbaldeston, who is also a C.J. Martin overseas biomedical fellow of the Australian National Health and Medical Research Council.
After just five days, she noticed the ears of mice lacking mast cells were surprisingly thicker than were the ears of normal mice, suggesting an accumulation of white blood cells. By injecting mast cells back into the deficient mice, Grimbaldeston found the immune-suppressing molecule the cells secrete to limit ear swelling: interleukin-10. She also identified which antibodies activated the mast cell receptors to trigger IL-10's release.
Trial injections of IL-10 have reduced inflammation in patients suffering from rheumatoid arthritis and psoriasis, with mixed results. Yet given the manufacturing cost of producing IL-10, Galli thinks it an unlikely practical treatment for poison oak or sun exposure.
The next studies will look into whether mast cells reduce the developm
|Contact: Brian Lee|
Stanford University Medical Center