Limitations of flow cytometry in the analysis of CD1a/HLADR+ human oral mucosal Langerhans cells

Abstract

Suspensions of human oral epithelial cells were stained with antibodies to CD1a and HLADR conjugated with fluorochromes and analysed by flow cytometry with the aim of purifying double-labelled Langerhans cells, a population comprising approximately 2% of the cell total. Whole suspensions had high levels of autofluorescence and a wide range of forward and right angle scatter properties. The mean percentage of CD1a/HLADR+ cells was 2.1%, though the double-labelled cells did not form a discrete group and the percentages of positive cells using control antibodies were similar. Density gradient centrifugation prior to flow cytometry did not facilitate Langerhans cell identification within the suspension. The results indicate flow cytometric analysis of minority cell populations (such as Langerhans cells) within oral epithelium is limited by the autofluorescence of physically heterogeneous keratinocytes, and emphasize the importance of controls in studies of oral epithelium which use this method.