Moderate to severe chronic obstructive pulmonary disease (COPD) could be an auto-immunity problem, a new study has found.
The researchers from Spain studied the presence of auto-antibodies in patients with COPD and compared them to levels of control subjects.
Their findings suggested that a significant number of patients with COPD had significant levels of auto-antibodies circulating in their blood, about 5 to 10 times the level in controls.
"We showed that between one third and one quarter of patients with clinically stable COPD present abnormal levels of circulating auto-antibodies in the blood. Our findings provide further support for the hypothesis that the pathogenesis of COPD involves an auto-immune component," said Jaume Sauleda, coordinator of respiratory medicine department, Hospital Universitari Son Dureta.
The researchers recruited 328 patients with clinically stable COPD three months after hospitalization for the first time with an exacerbation of the disease.
They collected information on current and past smoking habits, comorbidities, and data such as body mass index, degree of dyspnea and six-minute walk distance.
The reserchers then took blood samples and tested the blood for antinuclear antibodies (ANA), anti-tissue antibodies (AT) including mitochondrial (AMA), liver-kidney microsomal (LKM), smoothmuscle (SMA), and parietal gastric cell (PGC) antibodies. The serum levels of C-reactive protein were also tested in patients.
"We wanted to quantify the levels of auto-antibodies in COPD with respect to the patients' lung function and disease severity. By doing so, we hoped to determine whether in fact COPD had an auto-immune aspect," said Sauleda.
The researchers found that, overall, 34 percent of COPD patients had abnormally high levels of ANA titer-a prevalence 11 times higher than seen in the control group, and 7 times higher than reported in healthy subjects in previous studies.
Furthermore, 26 percent of the patients were positive for AT, a prevalence 4.5 times higher than in the controls, and 4 times higher than reported in healthy subjects in other studies.
Other studies have found that patients with "severe bronchitis" (which would probably be characterized as COPD today) had high levels of circulating ANA, and these results confirm those earlier findings.
"We can only speculate on the mechanisms underlying the observed associations. The prevalence of ANA and AT may be non-specific markers of an ongoing auto-immune response or may be directly involved in the pathogenesis of the disease. However, these alternatives are not mutually exclusive," said Sauleda.
The findings were published online ahead of the print edition of the American Thoracic Society's American Journal of Respiratory and Critical Care Medicine.