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30-01-2011 | Respiratory | Article

BMI linked to presence of antinuclear autoantibodies in COPD

Abstract

Free abstract

MedWire News: Low body mass index (BMI) is associated with an increased prevalence of antinuclear autoantibodies (ANAs) in patients with chronic obstructive pulmonary disease (COPD), research shows.

Writing in the journal Thorax, W Timens (University of Groningen) and team remark that the immune system is chronically activated in patients with COPD.

They explain: "Studies showing increased levels of ANAs indicate an antigen-specific self-reactive response in patients with COPD. In addition, increased levels of anti-elastin autoantibodies and T-helper 1 responses against elastin have been found in emphysema. This suggests the presence of antibody-mediated degradation of extracellular matrix which might contribute to sustained inflammation."

However, the researchers add that not all patients with COPD carry ANAs, "suggesting heterogeneity in the autoimmune response in COPD."

To investigate factors associated with ANA positivity in COPD patients, the researchers studied 124 patients with the lung disease and 108 age- and gender-matched controls without the condition. Of these, 94 COPD patients and 71 controls had a history of smoking.

Blood samples were collected from the participants and analyzed for ANAs. The antibody repertoire of B cells - lymphocytes that play major role in immune response - in lung tissue samples from eight COPD patients and eight controls was also assessed to investigate the role of B cells in autoantibody generation.

The team found that 44% of COPD patients tested positive for ANAs compared with just 22% of controls. Indeed, patients with COPD were 3.12 times more likely to test positive for serum ANAs than controls, after adjusting for age, gender, and other variables.

Among patients with COPD, ANA positivity was significantly associated with a low BMI of less than 22 kg/m2, at an odds ratio of 4.93 compared with a higher BMI.

ANA positivity was not associated with age, smoking status, gender, or pack-years of smoking in COPD patients, the researchers note.

They also found that the antibody repertoire of B cells in the lungs of patients with COPD had a high frequency (10.0%) of positively charged complementarity-determining region 3 protein residues - a feature associated with self-reactive antibodies - which was significantly higher than that in controls (6.7%).

Timens and team conclude: "The results show that COPD is a heterogeneous disease with respect to the prevalence of ANAs.

"ANAs are primarily associated with the presence of COPD and with low BMI, but not with smoking."

They add: "Our findings may help to achieve a better understanding of the multifactorial and complex disorder of COPD and to divide this heterogeneous population into relevant phenotypes."

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2011

By Mark Cowen

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