Objective: To study the association of free immunoglobulin light chain (FLC) with clinical manifestations and lung inflammation in smokers with normal lung function and chronic obstructive pulmonary disease (COPD) patients.
Methods: Thirty-two patients with peripheral lung cancer undergoing surgical resection were enrolled from the Department of Thoracic Surgery,Affiliated Hospital of Xuzhou Medical College. They were divided into non-smoking with normal lung function group (non-smoking group, 10 cases), smoking with normal lung function group (smoking group, 12 cases) and smoking with stable COPD group (COPD group, 10 cases). Their preoperative fasting serum and lung tissues away from cancer were used in the study.Enzyme-linked immunesorbent assays (ELISA) were used to detect the levels of FLC-λ and FLC-κ in serum and lung tissue homogenates. The expression of FLC-λ and FLC-κ in the airway epithelium, alveolar wall and blood vessel wall was detected by immunohistochemistry. The correlation between FLC levels and pulmonary functions were analyzed.
Results: The serum levels of FLC-λ and FLC-κ in COPD group and smoking group were (35 ± 11),(38 ± 12) and (26 ± 9),(26 ± 8) mg/L, respectively. They were all significantly increased compared with the non-smoking group [(16 ± 7),(16 ± 5) mg/L]. The differences were all statistically significant (q = 3.590-7.482, P < 0.01), and those of the COPD group were significantly higher than those of the smoking group (q = 3.209-4.198, P < 0.05 and P < 0.01). The concentrations of FLC-λ and FLC-κ in lung tissue homogenates of the COPD group and the smoking group were (1.29 ± 0.31),(1.32 ± 0.30) and (0.86 ± 0.42),(0.85 ± 0.37) µg/mg, respectively. They were all significantly increased compared with those of the non-smoking group [(0.45 ± 0.18),(0.42 ± 0.13) µg/mg],(q = 4.178- 9.795, P < 0.05 and P < 0.01). The levels of FLC-λ and FLC-κ in the lung tissue homogenates from the COPD group were significantly higher than those from the smoking group (q = 4.269-4.349, all P < 0.05). The expression of FLC-λ and FLC-κ was detected in airway epithelium, alveolar wall and blood vessel wall. The levels of FLC-λ and FLC-κ in serum and lung tissue homogenates showed a negative correlation with FEV1 percentage of predicted value (r = -0.476 to -0.591, all P < 0.01).
Conclusions: Expressions of FLC were increased in the serum and the lung tissues of COPD patients and smokers with normal lung function, and closely correlated with airflow limitation. The results suggest that FLC plays a proinflammatory role in the pathogenesis of COPD.