IL-8 in pleural effusion

Abstract

Interleukin-8 (IL-8) is a recently described potent chemotactic factor that may be involved in the pathogenesis of pleural effusions. To understand the actual mechanisms mediating the inflammatory response, changes in cellular components and IL-8 level in pleural fluid of different aetiologies were evaluated. Thirty-four patients (19 male, 15 female) with a mean age of 46 ± 22 years (range 16–92) were included in the study. Of these, 13 had tuberculous pleural effusion, seven had empyema/parapneumonic pleural effusion, and 14 had malignant pleural effusion (seven adenocarcinoma, three ovarian carcinoma, two lymphoma, one chronic myeloid leukaemia, and one small cell carcinoma) with positive cytology. Differential cell counts in the pleural fluid were obtained using cytocentrifuge preparations. The concentrations of IL-8 in pleural fluid were measured by the ELISA method. Interleukin-8 was detected in all 34 pleural fluid samples. The serum IL-8 level was analysed only in the empyema/parapneumonic pleural effusion group The mean IL-8 levels of tuberculous, empyema/parapneumonic, and malignant pleural effusions were 1420 ± 1049 pg ml −1, 4737 ± 2297 pg ml −1, and 1574 ± 1079 pg ml −1, respectively. The IL-8 levels in the empyema/parapneumonic group were significantly raised over malignant and tuberculous groups ( P<0·02). The mean pleural fluid neutrophil counts in tuberculous, empyema/parapneumonic and malignant pleural effusions were 315 ± 575 cells mm −3, 11 136 ± 12 452 cells mm −3, and 635 ± 847 cells mm −3, respectively ( P<0·003). There was a significant positive correlation between pleural IL-8 levels and neutrophil counts ( r=0·46, P<0·006). The levels of IL-8 in paired samples of serum and pleural fluid in the empyema/parapneumonic effusion group were compared, and the concentration of IL-8 was higher in the pleural effusion than serum (means, 4737 ± 2297 pg ml −1 and 130·0 ± 62·5 pg ml −1, respectively, P<0·03). There was a significant negative correlation between IL-8 concentrations in serum and pleural fluid ( r=−0·80, P<0·03). This data suggests that production of IL-8 in pleural effusion may play a key role in initiation and maintenance of inflammatory reactions, especially in empyema/parapneumonic pleural effusions. It may offer the basis for introduction of novel anti-inflammatory agents in treatment.