Use of the fluorescence-activated cell sorter to quantitate and enrich for subpopulations of human skin cells.

A variety of immunologic staining techniques were compared in a quantitative study of antigen expression by human epidermal cells. Virtually all nucleated epidermal cells express beta 2-microglobulin, which is associated with HLA-A, -B, and -C antigens, whereas only about 4% expressed T6, an antigen expressed by Langerhans cells but not other cells in the skin. With the fluorescence-activated cell sorter (FACS), epidermal cell suspensions were selectively enriched 10- to 15-fold for T6-positive Langerhans cells. An average of 6.5% of cells were specifically stained by anti-HLA-DR antibody. When dispersed cells stained with anti-DR plus peroxidase were examined with the technique of immunoelectron microscopy, only mononuclear leukocytes (probably Langerhans cells) were stained. After separating HLA-DR positive skin cells with the FACS, the DR-positive population but not the DR-negative population stimulated proliferation of allogeneic responder lymphocytes, indicating that sorted cells are metabolically active. We conclude that HLA-DR antigen is not expressed by keratinocytes in normal human skin cell suspensions and that the FACS can be used to selectively enrich or deplete skin cell suspensions of antigenically distinct subpopulations such as Langerhans cells.