Modification of surface marker expression on CD14 monocytes of allergic patients after lysis or Ficoll purification

It has been observed that peripheral blood monocytes are often in a primed or activated state in inflammatory diseases such as asthma. However, the majority of these studies have been performed using cells which have been purified by density gradient centrifugation on Percoll or Ficoll-Hypaque. Using cytofluorimetry, we compared the expression of monocyte surface markers of monocytes from untreated blood with monocytes purified by erythrocyte lysis or density centrifugation using the Ficoll technique. Monocytes from two groups of subjects were analyzed: healthy subjects and allergic patients. When compared with untreated blood, the percentage of CD16-positive cells, and the sMFI was significantly greater after monocyte purification (lysis or Ficoll). The expression of CD62L (percentage and sMFI) was modified after monocyte purification. Such modification of these two surface markers was predominantly observed on monocytes from allergic patients, and not on monocytes from healthy subjects. This study suggests that surface marker analysis should be performed on unfractionated whole blood in order to avoid modification of monocyte antigens.