Mechanisms of eosinophilia. 8. Importance of local cellular reactions in stimulating eosinophil production.

The mechanism of eosinophilia was studied in rats challenged by injection of larvae, with special reference to the role of local cellular reactions to the foreign substance. Parasitic material was given in different forms —intact larvae, homogenate, saline extract—and by different routes. Increased eosinophil production resulted only when a local cellular response had been provoked in some tissue. Nevertheless, even when given in a form or by a route which did not lead to eosinophilia, this treatment `primed' the recipient to give an augmented response to later challenge by an effective stimulus. The relevance of these findings to knowledge of the mechanism of eosinophilia is discussed.