Eosinophil infiltration and activation at the gastric ulcer margin in rats

Recruitment and activation of eosinophils have been studied intensely in asthma and other allergic diseases. Less is known about the infiltration and behaviour of eosinophils during gastric ulcer healing.

To examine the tissue infiltration and activation of eosinophils in the ulcer margin at different time points after ulcer induction (days 1-15).

Eosinophil peroxidase (EPO) staining and transmission electron microscopy (TEM) were used to observe eosinophil infiltration and activation in rats with acetic-acid-induced ulcer in the oxyntic mucosa. The distribution of macrophages was evaluated by immunocytochemistry using the macrophage-specific antibodies ED1 and ED2.

There was a prominent increase in eosinophils around the ulcer margin at day 1 after ulcer induction, which peaked at day 5. TEM revealed characteristic signs of eosinophil activation, including cytolysis and piecemeal degranulation. Eosinophil cytolysis was the major form of activation, seen most frequently at day 5. A few scattered apoptotic eosinophils could also be observed. In normal controls and sham-operated rats, activated eosinophils were detected rarely. The distribution pattern of infiltrated eosinophils closely resembled that of macrophages at the ulcer margin. However, in the central part of the granulation tissue (at day 5) only macrophages could be found.

There is marked infiltration and signs of activation of eosinophils together with macrophages at the margin of newly formed ulcers.