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Scientists supported by the National Institute of Allergy and Infectious Diseases (NIAID), part with the National Institutes of Health, have discovered that people with persistent sinus irritation have an exaggerated immune response to common airborne fungi. The results of their study appear online today within the Journal of Allergy and Clinical Immunology. “This study is the first to show a possible immunologic basis for persistent sinusitis, an important starting point to better fully grasp the etiology in the illness,” says Marshall Plaut, M.D., chief of NIAID’s allergic mechanisms section. Despite the enormous health impact of persistent sinusitis–nearly 30 million people were diagnosed with sinusitis in 2002, according to U.S. Centers for Disease Control and Prevention, and direct costs of the illness exceed $5.6 billion per year–the condition is very poorly understood, he states.
The scientists, led by Hirohito Kita, M.D., of the Mayo Clinic in Rochester, MN, compared blood samples taken from 18 people diagnosed with chronic sinusitis with blood samples from 15 healthy volunteers. Nasal secretions through the two groups were also examined for the presence of fungal proteins and inflammation-causing immune system molecules.
Airborne microscopic fungi spores abound indoors and out. People may inhale a million or more fungal spores each day, notes Dr. Kita. The mere presence of such fungi while in the airways, however, is not enough to trigger sinusitis because these spores can be found while in the upper respiratory tracts of both sinusitis sufferers and non-sufferers. Indeed, in this study, levels of fungal proteins in nasal secretions were similar in both groups.
The Mayo Clinic scientists looked for evidence that people with sinusitis respond abnormally to these harmless fungi. The investigators exposed immune cells derived from your blood samples to extracts of 4 common airborne fungi: Alternaria, Aspergillus, Penicillium and Cladosporium. The cells of chronic sinusitis sufferers released significant amounts of 3 immune-modulating chemicals, called cytokines, specifically interferon-gamma, interleukin-5 (IL-5) and IL-13. In contrast, cells from healthy volunteers released very little interferon-gamma and no IL-5 or IL-13. The most dramatic responses occurred after publicity to Alternaria.
Importantly, says Dr. Kita, the released cytokines represent both major classes of cytokines–interferon-gamma is inside the Th1 group and IL-5 and IL-13 are in the Th2 class. This is notable because scientists have thought that allergic reactions involve only Th2 cytokines, Dr. Kita explains. (While persistent sinusitis is not considered to be an allergic disease, people using the condition also often have asthma and allergic rhinitis, giving scientists cause to suspect a link.) The current findings add to an evolving understanding of allergic diseases that suggests symptoms may stem from a combination of Th1 and Th2 cytokines.
The combined effect of excess Th2 and Th1 cytokines released while in the presence of fungi may explain a number of chronic sinusitis symptoms, including persistent inflammation of sinus and nasal mucous passages, say the scientists.
Previously, Mayo clinic scientists used intranasal antifungal agents to successfully treat individuals with chronic sinusitis. While those studies generated controversy, in part because other researchers were unable to replicate the findings, Dr. Kita says modern report supports the rationale of treating chronic sinusitis with antifungals. Medical trials to further test antifungal treatment for persistent sinusitis are being planned, adds Dr. Kita.
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NIAID is a component with the National Institutes of Health, an agency from the U.S. Department of Health and Human Services. NIAID supports basic and applied research to prevent, diagnose and treat infectious diseases such as HIV/AIDS and other sexually transmitted infections, influenza, tuberculosis, malaria and illness from potential agents of bioterrorism. NIAID also supports research on transplantation and immune-related illnesses, including autoimmune disorders, asthma and allergies.
Reference: S-H Shin et al. Chronic rhinosinusitis: An enhanced immune response to ubiquitous airborne fungi. The Journal of Allergy and Medical Immunology. Published online Oct. 8, 2004. doi: 10.1016/j.jaci.2004.06.012.
Press releases, fact sheets and other NIAID-related materials are available on the NIAID Web site at
http://www.niaid.nih.gov.
Contact: Anne A. Oplinger
aoplinger@niaid.nih.gov
301-402-1663
NIH/National Institute of Allergy and Infectious Diseases