Israel Medical Association Journal

The induced sputum technique allows sampling of the airways in a non-invasive manner and thus offers a unique opportunity to identify biomarkers of potential clinical utility in respiratory medicine. Sputum cells were originally examined in stained smears and the procedure was applied in both research and clinical settings from the 1950s through the 1970s. The cells, recovered from spontaneous coughing, were used to study lung cancer and respiratory infections and, later on, to diagnose Pneumocystis carinii pneumonia in patients infected with human immunodeficiency virus. The method was largely improved by the induction of sputum with aerosol of hypertonic saline and was extended to become part of the assessment of airway inflammation in bronchial asthma and chronic obstructive pulmonary disease. It was recently shown that induced sputum can be used to study interstitial lung diseases and, more specifically, sarcoidosis, non-granulomatous ILD[1], occupational lung diseases and other systemic diseases with lung involvement.

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Patients with a compromised immune system suffer a wide variety of insults. Interstitial lung changes are one of the most common and serious complications in this group of patients. The morbidity rate reaches 50% and up to 90% if endotracheal intubation and mechanical ventilation are necessary. Opportunistic and bacterial infections are common causes of pulmonary infiltrates and must be distinguished from other conditions such as drug reactions, volume overload, pulmonary hemorrhage, and malignant diseases. Accurate and prompt diagnosis of potentially treatable causes can be life-saving. Non-invasive diagnostic methods for evaluation are often of little value, and an invasive procedure - such as bronchoalveolar lavage, transbronchial biopsy or even open lung biopsy - is therefore performed to obtain a histologic diagnosis. Yet, even when a specific diagnosis is made it may not improve the patient’s survival. Numerous textbook and review articles have focused on the management of this condition. The present review attempts to provide a comprehensive and systematic picture of current knowledge and an integrated approach to these challenging patients.

Background: Exposure of newborn animals to high concentrations of oxygen leads to diffuse alveolar damage similar to that seen in bronchopulmonary dysplasia in human infants. Therefore, neonatal rats are a suitable practical model of hyperoxic lung damage in human infants.

Objective: To determine the involvement of tumor necrosis factor-alpha and interleukin-6 in lung injury in neonatal rats exposed to 100% O2 concentration.

Methods: A randomized controlled study was designed in which litters of term Sprague-Dawley rat pups were assigned to experimental or control groups. The pups in the experimental group were placed in 100% O2 from birth for 9 days, while the control pups were placed in room air. Twelve to 15 pups from each group were sacrificed on day 1, 3, 6, 9 and 13 after birth for bronchoalveolar lavage collection and lung histologic study. The bronchoalveolar lavage fluid was assayed for TNFα and IL-6.

Results: Newborn rats exposed to 100% O2 for the first 9 days of life showed severe pulmonary edema and hypercellularity on days 1 and 3, which then improved to nearly complete resolution on days 6 and 9. Pulmonary TNFα was produced early on O2 exposure (day 3) and pulmonary IL-6 later (days 6 and 9).

Conclusions: Hyperoxia induces sequential production of pulmonary TNFα and IL-6, which corresponds to the severity of the pathological findings and the known inflammatory and anti-inflammatory role of these cytokines.

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TNFα= tumor necrosis factor-alpha

IL-6= interleukin-6