SELECTED ARTICLES FROM THE RECENT LITERATURE 2004

12/30/04

Aspects of eosinophil trafficking and function

Summary
Background - A prominent accumulation of eosinophils (Eos) is very common in IgE-mediated allergic reactions. However, the mechanisms by which Eos migrate from the bone marrow to and persist in sites of such allergic reactions are only now being understood.

Findings - The subject of Eos trafficking was reviewed recently in an editorial by Wardlaw (1). He pointed out that Eos normally do not accumulate in body tissues except in the G-I tract. The accumulation of Eos in allergic reaction sites involves: 1) increased formation of Eos in the bone marrow by actions of the cytokine IL-5; 2) Eos specific chemoattractants such as eotoxin causing Eos egress from the bone marrow; 3) interaction of the adhesion molecules VLA-4 (on Eos) and the selectins P-selectin and VCAM (on the endothelium of post-capillary venules) leading to slowing of Eos flow in the vascular lumen and subsequent Eos sticking to the endothelium; 4) emigration of Eos from the vascular lumen through the vessel wall and into extracellular tissue spaces induced and regulated by chemokines and activating factors elaborated in the inflammatory sites.

Once in the tissue site, how long do Eos persist there and how? Munitz and Levi-Schaffer reviewed the role of interaction between Eos and other cell types such as fibroblasts with which Eos come in contact (2). Indeed, such interaction with fibroblasts likely play a major role in the capacity of Eos to persist in allergic reaction sites for days to weeks in contrast to the much shorter presence of an individual Eos in the peripheral blood irculation.

Reference
1. Clin Exp Allergy 2004;34:676-79
2. Allergy 2004;59:286-74

Editor's Comments
Eos have fascinated both basic scientists and clinicians for years. It is now clear that Eos can exert pro-inflammatory and anti-inflammatory effects. Eos may also regulate activities of certain other cell types. Much of the damaging effects of Eos are due to released cationic (alkaline) proteins normally found in the cytoplasm of Eos.

 

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