Washington, Oct 24 Exposure to cigarette smoke might weaken immune cells' ability to remove bacterial infections from the lungs, specifically nontypeable Haemophilus influenzae (NTHI), a pathogen often associated with respiratory infections and the progression of respiratory disease, says a new study.

NTHI has been found to cause invasive diseases such as meningitis, sinusitis, pneumonia, and bronchitis.

It is also the pathogen most frequently isolated in the respiratory tract of patients with chronic obstructive pulmonary disease (COPD) and chronic bronchitis.

Alveolar macrophages are part of the lungs' innate defense system and they play an essential role in the clearance of bacterial infections.

The research team has found that cigarette smoke may disrupt the capability of alveolar macrophages to clear NTHI from the lungs.

During the study, the research team from Spain and UK observed the effect of cigarette smoke in macrophage cell lines and human alveolar macrophages obtained from smokers and patients with COPD and found that cigarette smoke extract impaired the alveolar macrophage process.

Additionally, cells exposed to cigarette smoke extract were treated with glucocorticoid, an anti-inflammatory drug commonly used to treat respiratory conditions, and results showed that the drug did not compensate for the impairment to the alveolar macrophage process caused by the cigarette smoke.

"This study revealed novel effects of cigarette smoking on alveolar macrophage physiological functions which could contribute to lung bacterial colonization by opportunistic pathogens, such as NTHI," said the researchers.

The study appears in journal Infection and Immunity. (ANI)