Methyl ester of N-formylmethionyl-leucyl-phenylalanine: chemotactic responses of human blood monocytes and inhibition of gold compounds.

N-formylmethionyl-leucyl-phenylalanine, a potent hemotactic peptide for human polymorphonuclear leukocytes, is less chemotactic for human blood monocytes. Esterification of the N-formylated tripeptide enhances its chemotactic activity for monocytes by more than 4 logs, whereas a decrease by 3 logs is observed for polymorphonuclear leukocytes. These results indicate the participation of the C-terminal carboxyl group in chemotaxis of different cell types. We have also observed the selective inhibition of chemotactic responsiveness of human blood monocytes by a clinically useful antirheumatic drug, sodium aurothiomalate. Since this is the first in vitro cell migration model of inflammation in which gold compounds have demonstrated activity in micromolar concentrations, it suggests a site of action for this antirheumatic drug.