CONTACT: L. E. OHMAN
283 Medical Laboratories
Iowa City IA 52242
(319) 335-6660; fax (319) 335-8034
UI researchers study why some are protected from farmer's lung
IOWA CITY, Iowa -- Repeated exposure to molds often found in damp hay
and grain can irritate the lungs causing a disease known as farmer's lung
or hypersensitivity pneumonitis. The syndrome causes coughing and shortness
of breath and is "reasonably common in the Midwest," says Dr.
Gary Hunninghake, University of Iowa professor of internal medicine, who
has studied the disease for many years.
People do not need to be in direct contact with hay or grain to be exposed
to the molds, Hunninghake notes. The spores travel in the air and can settle
in air conditioners and car air-cooling systems.
Activation of the immune system is necessary for the development of
farmer's lung, and many people exposed to the molds develop antibodies;
however, not everyone gets the disease. Only 10 to 15 percent of the people
exposed to the molds get farmer's lung, while others get asthma or are
The cause of this varied response to the molds remains elusive. It is
one of the puzzles of the disease Hunninghake would like to solve.
He and co-investigator, Dr. Gunnar Gudmundsson, also in the department
of internal medicine, moved a step closer to that goal when they identified
a specific immune system protein, interferon-gamma, that is necessary for
the development of hypersensitivity pneumonitis. These findings were reported
in the May 15 issue of the Journal of Clinical Investigation.
Interferon-gamma is present in all humans and is one of three types
of interferon. The others are interferon-alpha and interferon-beta.
Hunninghake and Gudmundsson found that mice genetically altered to have
no interferon-gamma did not develop hypersensitivity pneumonitis after
repeated exposure to the molds, while mice with the protein did develop
the disease. Further, when interferon-gamma was replaced in the mice lacking
the protein, they too developed farmer's lung after repeated exposure to
The fact that immune system activity is necessary to develop the disease
did not surprise Hunninghake. He says it is common that hypersensitivity
pneumonitis develops when immune system activity is increased, for example,
following a cold. As an analogy, he notes that asthma is often worse after
a viral infection.
These findings set the stage for further investigation into the factors
that protect some people and not others from developing farmer's lung.
Hunninghake believes the answer may be found in a complex combination of
genetic makeup, degree of exposure to the mold and activity level of the
"When we get the riddles worked out in the animals, we'll move
on to the patient studies," Hunninghake says. "When you test
this in people, you want to know what you're looking for."