Eosinophils and mediators of anaphylaxis. Histamine and imidazole acetic acid as chemotactic agents for human eosinophil leucocytes.

Histamine and one of its major catabolites, imidazole acetic acid (ImAA), were selectively chemotactic for human eosinophils, whereas L-histidine and other histamine catabolites including 1,4-methylhistamine, 1-methyl-4-imidazole acetic acid and N-acetylhistamine were inactive in eosinophilotaxis over a large dose range. The dose response for histamine was dependent on the chemotaxis incubation time and the source of eosinophils, although the latter was not clearly associated with particular disease states. When histamine and ImAA were combined the chemotactic response was similar to that obtained when one agent was assayed alone, no additive or synergistic effects being observed. There was cross-deactivation between histamine and ImAA. These experiments suggest that histamine and ImAA activate the same chemotactic recognition mechanism for eosinophils. Thus ImAA joins histamine and the tetrapeptides (ECF-A) as anaphylaxis-associated selective chemoattractants for human eosinophils