Casein-mediated neutrophil chemotaxis: a parallel between surface binding and chemotaxis

This study was directed toward demonstrating an interaction between human polymorphonuclear leukocytes (PMNs) and the chemotactic factor,casein. Experiments conducted using fluorescein-labeled casein indicated that PMNs have a membrane receptor for this chemotactic factor. This receptor was specific for casein and was not found on lymphocytes. A direct parallel was shown between the binding of FITC--casein and the PMN chemotactic response to this protein. Binding to the receptor was optimal at 25 degrees C, unaffected by sodium azide, and partially reduced by iodoacetate. Enzymatic treatment of PMNs with pronase and trypsin resulted in a loss of both FITC--casein-mediated PMN fluorescence and chemotaxis. Our data indicate that human PMNs have a membrane receptor for casein and that interaction with this receptor results in a chemotactic response.