Flow cytometric analysis and sorting of HLA-DR+CD1+ Langerhans cells

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Abstract
There is a considerable need for reliable methods for enumeration and enrichment of Langerhans cells (LCs), since they continue to be the subject of intensive investigation in normal and diseased skin. It has been claimed that standard labelling with either anti-HLA-DR or OKT6 antibodies alone may fail to identify potentially important subsets of LCs with the phenotypes HLA-DR+CDI- and HLA-DR-CDI+. We report here on flow cytometric analysis of suction blister-derived normal epidermal cell (EC) suspensions, double stained with phycoerythrin-conjugated anti-HLA-DR and fluoresceinated OKT6. In seven separate experiments, no evidence for the existence of either HLA-DR+CDI- or HLA-DR-CDI+ECs was obtained. We found that HLA-DR+CDI+LCs, which constituted a mean of 2.5% (.+-. 0.3 SEM) of all ECs, could be readily identified on the basis of fluorescence, and that their light scatter characteristics were those of moderately sized cells of low granularity. We further describe our method for flow cytometric enrichment of such HLA-DR+CDI+ LCs for functional studies, based on selection on both fluorescence and light scatter criteria. Enrichment is to greater than 90% purity, and the method is applicable to the small number of ECs (approximately I .times. 106) obtained from a suction blister.