Interleukin-8 (IL-8), a potent pro-inflammatory cytokine, has been shown to have chemotactic activity for neutrophils, lymphocytes, and basophils. Effects of IL-8 on eosinophil chemotaxis are unresolved. Because eosinophils accumulate at the site of allergic inflammation and may play a role in the pathogenesis of asthma, we investigated the eosinophilotactic capacity of IL-8. We examined the ability of IL-8 to induce human eosinophil migration across 3-microns pore naked filters, and human umbilical vein endothelial cell and human pulmonary type II-like epithelial cell (A549) monolayers cultured on these filters. IL-8 induced similar dose-related eosinophil migration through all three barriers. Kinetic experiments indicated more rapid migration through noncellular barriers but equivalent migration through all barriers by 3 h. Chemotactic/chemokinetic data show that IL-8-induced eosinophil migration is chemotactic. We also determined that the ability of IL-8 to induce transcellular migration was unique in comparison with other cytokines and was not dependent on the use of fresh vs. passaged monolayer cells as barriers. Therefore our data indicate that IL-8 may play a significant role in tissue eosinophilia observed in allergic respiratory diseases.

Neutrophils, eosinophils and cytokines are important in allergic airway inflammatory responses. However, it is unclear how cytokines selectively influence neutrophils versus eosinophils to migrate to an inflammatory site. The cytokines, transforming growth factor-beta1 (TGF-beta1), interleukin (IL)-1alpha, IL-5, IL-8, granulocyte macrophage-colony stimulating factor (GM-CSF) and tumor necrosis factor-alpha (TNF-alpha), are released subsequent to allergic reactions and affect both neutrophil and eosinophil functions. We studied whether these cytokines differed in capacity to induce human neutrophil versus eosinophil migration through naked filters and human umbilical vein endothelial cell (HUVEC) and human pulmonary type II-like epithelial (A549) cell monolayers grown on filters. Dose-response experiments using all barriers were performed for each granulocyte and cytokine. TGF-beta1 did not induce granulocyte migration. IL-5 induced eosinophil migration only through naked filters. IL-1alpha stimulated neutrophil migration through cellular barriers, but not through naked filters. TNF-alpha and GM-CSF induced neutrophil and eosinophil migration through filters, but only neutrophil migration through cellular monolayers. Only IL-8 induced significant neutrophil and eosinophil migration; however, there were clear-cut differences between the neutrophilotactic and eosinophilotactic responses through all barriers employed. Thus, our data show that these cytokines induce distinct chemotactic responses for neutrophils versus eosinophils. Moreover, by using relevant cellular barriers versus naked filters, our data better examines the capability of these cytokines to induce selective granulocyte migration to an inflammatory site in lung diseases such as asthma.

Interleukin (IL)-8 is a potentially important cytokine in allergic respiratory responses since it is released by many resident lung cells, and it is a potent granulocyte chemoattractant. Therefore, we induced an immunoglobulin (Ig)E-mediated response in human lung samples and studied whether IL-8 was produced in sufficient quantities to promote human neutrophil and eosinophil migration across naked filters and endothelial and pulmonary epithelial monolayers cultured on these filters. Fresh human lung fragments from 16 thoracotomy specimens were treated with either a 1:100 dilution of anti-IgE or buffer (control) for 30 min. All anti-IgE treated lung samples had significant release of histamine and neutrophil and eosinophil chemotactic activity. Fourteen of the 16 lung samples had a significant increase in IL-8 subsequent to anti-IgE treatment (p<0.01). Anti-IL-8 antibody (4 microg x mL[-1]) inhibited 42% and 53% of neutrophil and eosinophil chemotactic activity respectively, contained in supernatants from anti-IgE-treated lung samples. Finally, we found that IL-8 at a concentration near that measured after anti-IgE treatment of lung samples (2,000 pg x mL[-1]) induced neutrophil and eosinophil migration through naked filters and endothelial and pulmonary epithelial cell monolayers. Thus, human lung IgE-mediated responses in vitro results in the rapid release of interleukin-8 in amounts sufficient to affect a biological response, granulocyte transcellular migration, indicating that interleukin-8 may play a significant role in allergic respiratory diseases.

Multiple molecular species of the eosinophil chemoattractant platelet activating factor (PAF) are produced as a result of inflammatory processes. We therefore compared the ability of three naturally occurring PAF species (C16:0, C18:0, and C18:1), which only varied at carbon 1, to induce eosinophil chemotaxis through naked 3-microns pore polycarbonate filters. Timecourse experiments indicated that all species of PAF tested induced significant and equivalent eosinophil migration at 1 h which peaked at 2 h. Overall, the rank order of chemotactic potency for the PAF species was relatively equivalent. The specific PAF antagonist WEB 2086 inhibited eosinophil migration induced by all three PAF species equally. We conclude that the degree of PAF-induced eosinophil migration is not dependent upon the molecular species of PAF.