Chemotactic Factor Binding and Functional Capacity: A Comparison Between Human Granulocytes and Differentiated HL‐60 Cells

Inthe presence ofdimethylsulfoxlde(OMSO), the leukemic promyelocyticcemmlineHL60 willdifferentiate Intomature poiymorphonuclear granulocytes. inthe presentreport, we compare chemotactic factorbindIngand functionInHL-60 cellswiththatof normal human granulocytes usingthe chemotactic peptideN-formylmethionyl-leucyl-phenylaianine(FMLP) as ligand.The cellular response measured asCL was changed as a result of storage or condItIoning of normal peripheral blood cells. With these cells, a conditioning procedure at room temperature resulted in a pronounced increase in the CL re sponse. The increaseofthe CL response was probablya resultofincreasedexpressIon ofcrypticreceptors, sincethe changes of the oxidatlve response to FMLP was accompanied by increased bInding of the peptide to the cellsurface.Scatchard analysis revealedthatthe increasedbinding was due to an increased number of receptors. In differentiated HL-60 cells,condItioningneitherled toincreasedproductionofoxidative metabolites, nor to any increased bindIng of the peptide. The data thus Indicate that many FMLP receptors could resideina crypticsitethatisnotaccessibletoextracellular ligands,and that condItioningresultsin an increased exposure of these receptors, followed by an increased oxidativeresponse to the ligandin normal cellsbut not in mature HL-60 cells.