ALTERED EXPRESSION OF CD11B CD18 AND CD62L ON HUMAN MONOCYTES AFTER CELL PREPARATION PROCEDURES/

We have investigated the effect of different cell preparation procedur es on the surface expression of CD11b/CD18 and CD62L on human monocyte s. Both EDTA and heparin anticoagulated blood were used as sources for leukocytes. The monocytes were analysed by flow cytometry in a mixed leukocyte suspensions obtained after ammonium chloride mediated lysis and in mononuclear cell suspension prepared by density gradient centri fugation (Ficoll-Paque) performed both at 4 degrees C and at 20 degree s C. Monocytes from heparinized blood had a higher expression of CD11b /CD18 and a more pronounced inter-individual variation than monocytes from EDTA blood. Monocytes isolated by Ficoll-Paque had a higher degre e of ex vivo activation by means of altered expression of CD11b/CD18 a nd CD62L compared to monocytes prepared by ammonium chloride mediated lysis. This was more pronounced when the isolation procedure was perfo rmed at 20 degrees C. Our findings indicate that monocytes prepared by ammonium chloride mediated lysis of EDTA blood and with the cell hand ling temperature kept at 4 degrees C are exposed to the smallest ex vi vo modulation by means of receptor alteration. An awareness of ex vivo modulation by different cell preparation procedures is of importance especially when comparing the expression of functional receptors on le ukocytes of disparate origin.