Limitations of flow cytometry in the analysis of CDIalHLADR+ human oral mucosal Langerhans cells

Suspensions of human oral epithetial cells were stained with antibodies to CD la and HLADR conjugated with fluorochromes and analysed by flow cytometry with the aim of purifying double-labetled Langerhans cells, a population comprising approximatety 2% of the cell total. Whole suspensions had high levets of autofluorescence and a wide range of forward and right angle scatter properties. The mean percentage of CDIalHLADR+ cells was 2.I%, though the double-labetled 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 Langerhanr cell identification within the suspension. The results indicate flow cytometric analysis of minority cell populations (such as Langerhans cells) within oral epithetium is limited by the autofluorescence of physically heterogeneous keratinocytes, and emphasise the importance of controls in studies of oral epithetium which use this method.