Different concentrations of chemotactic factors can produce attraction or migration inhibition of leukocytes.

Parallel tests were conducted utilizing, the capillary tube migration test and the Boyden chamber assay, in order to determine whether the decrease in leukocyte chemotaxis that occurs if overoptimal cytotaxin concentrations are applied is due to migration inhibition. Overoptimal doses of casein produced decreased chemotactic response and migration inhibition for both rabbit macrophages and neutrophils. However, guinea pig neutrophils exhibited no decrease in chemotaxis despite high casein doses. Overoptimal doses of acid-denatured anaphylatoxin produced a decreased chemotactic response and migration inhibition of neutrophils. In both assays, this agent showed no effect upon macrophages. It is concluded that a chemotactic signal at different concentrations can elicit unidirectional migration or migration inhibition. Accordingly, chemotactic leukocyte attraction could be antagonistically regulated not only by serum-derived and lymphocyte-derived migration inhibitory factors but also by high doses of the chemotactic factor itself. Thus, the Boyden chamber technique can measure both chemotactic migration and migration inhibition phenomena.