Bacterial Colonization Has Negative Impact in COPD

A recent study has shown that bacterial colonization could slow down the systemic, innate immune response in patients with chronic obstructive pulmonary disease (COPD). The study was conducted by Vincent S Fan, MD, MPH, of the VA Puget Sound Health Care System in Seattle, WA, and colleagues, and was published in the International Journal of COPD on March 4, 2016.

Although it is well-known that bacterial colonization is not unusual in patients with COPD, even those who are stable, the authors of this study say they “sought to better understand the relationship between COPD severity and innate immune responses” through their investigation.

They explain, “Toll-like receptors (TLRs) constitute a family of eleven transmembrane proteins that differentially recognize microbial products containing highly conserved motifs known as pathogen-associated molecular patterns (PAMPs).”

The relationship between TLRs and PAMPs is a critical part of the immune system’s response and ability to adapt.

Study participants were recruited from a clinic in Seattle, and the researchers had difficulty in finding enough patients who met their criteria, which included particular FEV1 results, being aged 50-89 years old, more than 10 pack cigarette years smoking, and no treatment with prednisone or antibiotics in the previous 4 weeks. The researchers modified the criteria for 6 of the participants.

If no spirometry results were available, the test was performed, the subjects completed a questionnaire regarding symptoms, smoking history, exacerbations, and bronchitis. Then, according to the researchers, “Subjects were asked to avoid vigorous exercise, alcohol, and nonsteroidal anti-inflammatory medications in the 24 hours preceding phlebotomy, which was performed between 8 am and 10 am to minimize circadian variations in cytokine responses.”

The researchers say, “In a small sample of well-characterized COPD subjects, we found that those with severe COPD have decreased whole blood leukocyte responsiveness to PAMPs ex vivo as compared to subjects with less severe COPD.” Although there were several limitations to this study, including the small sample size, the researchers say that future studies should investigate the mechanisms underlying the downgraded immune response, as well as the clinical consequences.