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Monday, November 18, 2013

Chronic sinusitis may be linked to an hyperactive immune system

A recent study in JAMA Otolaryngology--Head& Neck Surgery, in October 2013, suggested that chronic rhinosinusitis (CRS) may be caused by an overactive immune response to normal microbes, and not necessarily to bacterial infection. Investigators from Saint Louis University School of Medicine in Missouri lead by Dr. Rajeev Aurora found that patients and healthy controls tended to have qualitatively similar microorganisms in their sinus cavity. While control patients sinus lavage samples triggered interleukin (IL)-5 production in peripheral blood leukocytes from patients, this did not occur with leukocytes from controls.

The investigators obtained sinus cavity samples from thirty patients with CRS and 12 controls. They used deep sequencing to characterize the patients' microbiomes and search for pathogens that may potentially trigger an immune response. They also identified the immune cells and cytokines in the specimens. Almost all the recovered fungal and bacterial species were non pathogenic . Although there were higher numbers of these organisms in patients than in controls, the microbiomes in the two groups were qualitatively similar. The fact that only leukocytes from patients with CRS reacted to nasal samples from controls, suggests that CRS patients have an abnormal immune response to normal microorganisms.

The researchers postulated in an interview with Reuters Health that these results indicate that immune cells from a patient with CRS are getting activated by the microbes found in the normal sinus. These non-virulent organisms are most likely picked up from the air the patients breath, and therefore antibiotics cannot eliminate them in the sinus as they re-colonize the sinus with each breath. The authors also believe that these organisms may leads to a persistent inflammation in people whose immune system is aberrantly sensitive to these common organisms.

In an interview with Reuters Health  Dr. Itzhak Brook, a pediatrician at Georgetown University in Washington, D.C., who specializes in sinus infections, called the study "innovative and provocative." However, he noted that 16 of 30 patients in the CRS group were asthma suffers and prone to allergies. "They therefore do not represent the average patient with CRS, but a subgroup in whom the immune system is hyperactive," Dr. Brook added that the findings shouldn't change how doctors treat patients. The fact that the sinus cavity in normal individuals harbors the same bacteria (albeit in greater numbers) as infected sinuses is not new and was describe in study done by Dr. Brook in 1981.  

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