Eotaxin levels in pleural effusions: comparison with monocyte chemoattractant protein-1 and IL-8

In order to investigate the role of eotaxin in pleural diseases, we measured eotaxin in pleural effusions and studied the relationship between eotaxin levels and recruitment of inflammatory cells, particularly eosinophils. Interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) levels were also measured for comparison.

We evaluated 47 pleural effusion samples, 7 transudates and 40 exudates. The exudates consisted of 19 malignant, 11 tuberculous, and 5 parapneumonic effusions, and 5 effusions of other etiologies. Chemokine levels were measured by specific sandwich enzyme-linked immunosorbent assays.

Eotaxin was detected in all samples examined, but the levels did not differ significantly among the exudates. There was no significant correlation between the levels of eotaxin and MCP-1 or IL-8. The level of eotaxin but not the others was significantly higher in eosinophilic effusions (>10% eosinophils among white blood cells in the fluid) than in non-eosinophilic fluids. The number of eosinophils in pleural effusions was significantly correlated with the eotaxin levels, but not with the levels of other chemokines. The number of neutrophils was significantly correlated with IL-8 but not with the others.

Results suggest that eotaxin contributes to the migration of eosinophils in pleural inflammation. Taken together with the correlation between IL-8 and neutrophils, it appears that the predominant type of pleural inflammatory infiltrate is controlled, at least in part, by the subgroup of chemokines expressed in the pleural space.