Countergradients of Nonchemotactic Ligands for N -Formylmethionylleucylphenylalanine (FMLP) Receptors Promote FMLP-Induced Chemotaxis

Abstract

Using the under-agarose chemotaxis assay, addition of compounds known to inhibit chemotaxis of leukocytes toward N-f-Met-Leu-Phe (FMLP) was made to the first well in a line of three wells, leukocytes to the middle well, and a slight excess of FMLP to the third well. The compounds included rifampin, fusidic acid, carbobenzoxy Phe-Met, phenylbutazone, sulfinpyrazone, sulfasalazine, and sulfapyridine. The countergradients created in this system markedly stimulated, not inhibited, locomotion toward FMLP. These results, based on functional responses, confirm data using radiolabeled FMLP and support the hypothesis that these compounds are nonchemotactic ligands for FMLP receptors.