An eosinophilotactic factor derived from rat mast cells.

Rat eosinophils have been showed to respond chemotactically to the supernatant from mast cells which have been disrupted by freezing and thawing and from mast cells which have been specifically degranulated by Compound 48/80 or by antigen challenge or sensitised cells. The fact that the chemotactic response is not dependent on allergic degranulation suggests that the chemotactic factor is present pre-formed in the mast cells rather than being generated in response to an antigen-antibody reaction.