Ultrastructural immunogold labelling of human Langerhans cells enriched epidermal cell suspension

Colloidal gold particles are well suited as markers in electron microscopy. Indirect immunogold staining was used to identify cell membrane antigens defined by monoclonal antibodies OKT6 and BL6 on human Langerhans cells (LC) in suspensions. Isolated epidermal cells were obtained by skin trypsinization and enriched or depleted in OKT6 positive on BL6 positive LC using the panning method: incubation of OKT6 or BL6 preincubated cells on immunoglobulin coated dishes. Indirect immunogold staining was then performed after prefixation in 2% paraformaldehyde. In LC enriched suspensions, only LC exhibited a specific membrane labelling with OKT6 or BL6 recognized by the presence of small evently distributed gold granules. Neither Birbeck granules, nor other cytoplasmic organelles, were labelled. No other epidermal cells were found positive. In LC depleted suspensions, no labelling was observed. Immunogold labelling on LC enriched suspensions after panning is now in progress for the qualitative evaluation and the quantitative analysis of cell surface constituents and antigens expressed by human dendritic epidermal cells.