QUANTIFICATION OF CD1A, HLA-DR, AND HLA CLASS-I EXPRESSION ON VIABLE HUMAN LANGERHANS CELLS AND KERATINOCYTES

In order to determine precisely the cellular density of surface molecu les that are critical for antigen presentation in human epidermis, we utilized a quantitative immunofluorescence indirect assay and performe d flow cytometric analysis of human epidermal cell (EC) suspensions. W e first demonstrated that Tricolor-labeled streptavidin coupled to Cy- 5 (SA-TC) was a reliable marker for non viable EC and that SA-TC+ EC a ccounted for the frequent nonspecific background of fluorescence due t o isotype controls binding, although Langerhans cells (LC) and Keratin ocytes (Kc) express Fe receptors for IgG on their surfaces. These resu lts indicate that quantification of cell surface antigens on human EC requires the concomitant use of a marker of viability. Multicolor flow cytometric analysis allowed us to quantify CD1 molecules and major hi stocompatibility complex (MHC) antigens on viable human LC and Kc. Our results demonstrated a weak expression of MHC class I molecules on vi able LC (163 +/- 19 x 10(3) molecules/cell) compared to viable Kc (785 +/- 110 x 10(3) molecules/cell). Mean antigen density of HLA-DR and C D1a molecules on viable LO were 579 +/- 82 x 10(3) molecules/cell and 1600 +/- 133 x 10(3) molecules/cell, respectively. Quantitative flow c ytometry of viable EC may be proposed to evaluate the number of membra ne antigens whose level of expression is related to cellular maturatio n or activation that occurs in skin diseases. (C) 1996 Wiley-Liss, Inc .