MRP4 expression on human cutaneous DCs. Human skin was stained with isotype control antibody or the Mab M₄I-10 to detect MRP4. (A) An overview of the skin section (original magnification, 100×) and (B) details of MRP4-positive cells within the epidermis (left) or dermis (right) are shown (original magnification, 400×). (C) Epidermis was stained for MRP4 (red, Cy³ ) and CD1a (green, fluorescein-labeled tyramine; original magnification, 400×). Both MRP4 and CD1a are expressed in the same cells (merge). MRP4 signals were weaker than CD1a signals and were therefore measured with a longer shutter time. (D) CD1a⁺ epidermal (left) and dermal (right) cells were isolated by magnetic bead sorting and analyzed for CD1a and Langerin expression by flow cytometry and cytospins were stained for MRP4 expression (original magnification, 400×).