Adhesion molecules on eosinophils in acute eosinophilic pneumonia

Eosinophilic pneumonias

This review starts with discussions of several infectious causes of eosinophilic pneumonia, which are almost exclusively parasitic in nature. Pulmonary infections due specifically to Ascaris, hookworms, Strongyloides, Paragonimus, filariasis, and Toxocara are considered in detail. The discussion then moves to noninfectious causes of eosinophilic pulmonary infiltration, including allergic sensitization to Aspergillus, acute and chronic eosinophilic pneumonias, Churg-Strauss syndrome, hypereosinophilic syndromes, and pulmonary eosinophilia due to exposure to specific medications or toxins.

Intercellular adhesion molecule-1 on eosinophils is involved in eosinophil protein X release induced by cytokines

Recent evidence suggests that adhesion molecules play important roles in eosinophil functions such as degranulation and superoxide anion production. CD11b/CD18 (Mac-1) and CD49d/CD29 (VLA-4) are involved in eosinophil-endothelial adhesion through their counterligands, intercellular adhesion molecule-1 (ICAM-1; CD54) and vascular cell adhesion molecule-1 (VCAM-1), respectively. CD54 is also induced on eosinophils by cytokine stimulation. We hypothesized that CD54 on human eosinophils may participate in eosinophil degranulation. CD54 was induced on eosinophils by a combination of human recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF) and human recombinant tumour necrosis factor-alpha (rTNF-alpha) within 2 hr of incubation, as determined by flow cytometric analysis. Recombinant GM-CSF alone induced a slight but significant CD54 expression on eosinophils. Release of eosinophil protein X, an indicator of eosinophil degranulation, was induced by rGM-CSF and this effect was synergistically enhanced by adding rTNF-alpha. To determine the role of newly expressed CD54 in eosinophil degranulation, a blocking assay was performed using monoclonal antibody (mAb) against CD54 and CD18. Anti-CD18 mAb and anti-CD54 mAb markedly inhibited eosinophil degranulation induced by rGM-CSF or a combination of rGM-CSF and rTNF-alpha. On the other hand, anti-CD54 mAb had little effect on rGM-CSF- or rGM-CSF/rTNF-alpha-induced adhesion of eosinophils, whereas anti-CD18 mAb significantly inhibited eosinophil adhesion. These results indicate that CD54 on eosinophils plays an important role in the eosinophil degranulation and that eosinophils are capable of interacting with other beta 2 integrin-positive cells.

Analysis of recombinant human tumour necrosis factor-alpha-induced CD4 expression on human eosinophils

We examined the hypothesis that one of the pro-inflammatory cytokines, tumour necrosis factor-alpha (TNF-alpha), could induce expression of the adhesion molecule CD4 on human eosinophils. We further examined the effector function of CD4 and the mechanisms regulating CD4 expression. Human eosinophils were cultured with various concentrations of recombinant human TNF-alpha (rhTNF-alpha) with or without various drugs for 24 hr. After culture, eosinophils were stained for CD4 using a monoclonal antibody and then analysed by flow cytometry. Eosinophil-derived neurotoxin (EDN) release as eosinophil degranulation was examined by cross-linking of CD4 on eosinophils. The rhTNF-alpha induced CD4 expression on human eosinophils in a dose- and time-dependent fashion; rhTNF-alpha-induced CD4 expression was significantly inhibited by 10(-6) M cycloheximide, 10(-8) M dexamethasone, or 10(-6) M herbimycin A. Recombinant human interferon-gamma inhibited rhTNF-alpha-induced CD4 expression in a dose-dependent manner. However, cross-linking of CD4 on eosinophils did not evoke EDN release, suggesting that newly expressed CD4 molecules on human eosinophils do not play any role in triggering degranulation. Our data indicate that TNF-alpha-induced CD4 expression on human eosinophils is dependent on protein synthesis and may be dependent on tyrosine kinase activity.