In a surprise finding, scientists have discovered that histamine, the inflammatory compound released during allergic reactions that causes runny nose, watery eyes, and wheezing, can be produced in large amounts in the lung by neutrophils, the white blood cells that are the major component of pus.
Pus, a fluid found in infected tissue, is produced as a result of inflammation.
The study in mice is the first to show that lung neutrophils can produce histamine in significant quantities, according to principal investigator George Caughey, MD, chief of pulmonary/critical care medicine at the San Francisco VA Medical Center.
“Previously it was thought that the primary sources of lung histamine, in health as well as disease, was mast cells, which are classically associated with allergy,” said Caughey, who is also a professor of medicine at the University of California, San Francisco.
Caughey says the result could mean that histamine acts as a link between airway infections and asthma and bronchitis, which are associated with allergy. “In both, we observe inflammation––swelling, blood vessel leak, and muscle contraction that narrows the airway.”
The study appears in the January 2007 issue of the Journal of Experimental Medicine.