Electron microscopic observation of eosinophils migrated to the thoracic cavity of Litomosoides carinii-infected mice.

In order to study the role of eosinophils in filarial infection, ddY mice were inoculated with 20 Litomosoides carinii 7-day larvae each by the artificial pneumothorax technique. Migrated cells and larvae were collected from the thoracic cavity of the infected mice weekly from the 1st to the 8th week after infection and prepared for transmission electron microscopic observation. The number of migrated eosinophils and the proportion of eosinophils in the total migrated cells reached a peak at the 5th week. At the same time, eosinophils with low density granules were observed in both unattached and attached cells. In particular, many attached eosinophils with low density granules were observed directly on the worm surface. These observations strongly suggest that eosinophils are associated with attack on filarial worms.