DURHAM, N.C.--Researchers at Duke University Medical Center have discovered that mast cells -- the same cells responsible for the miseries of allergy -- also recognize harmful bacteria such as Salmonella and dangerous strains of E. coli and alert the immune system to destroy the bacteria.
The researchers say the discovery, which appears in the July 6 issue of the Proceedings of the National Academy of Science, may lead to new ways to fight infections, particularly in patients whose immune systems are compromised during an organ transplant or HIV infection.
The research is supported by grants from the National Institutes of Health and the Medical Research Council.
"For years people have wondered why we have mast cells when they seem to do nothing but cause misery for people with allergy and asthma," said microbiologist Soman Abraham, lead investigator of the study. "Now we've shown that the mast cell has a crucial role in identifying potentially dangerous bacteria and alerting the immune system to destroy them."
The much maligned mast cells lie just beneath the surface of virtually all body tissues that have contact with the outside world: the skin, gut, nasal passages, lung and urinary tract. For years mast cells seemed only to be a sort of cry-wolf cell that overreact to the inhalation of substances as benign as pollen grains and release a flood of inflammatory molecules and histamine -- the bane of allergy sufferers.
But Abraham and his colleagues discovered a more subtle but powerful
role for mast cells. The researchers found a molecule called CD48 on the mast
cell surface. CD48 recognizes a protein called FimH on the tips of hair-like
projections on many infectious bacteria. This CD48-FimH connection triggers mast
cells to alert the immune system by releasing a substance called tumor necrosis
factor alpha (TNF-a), which is a type of early warning system of infection,
Contact: Karyn Hede
Duke University Medical Center