Enrichment of epidermal Langerhans cells by immunoadsorption to Staphylococcus aureus cells

In addition to keratinocytes and melanocytes, the mammalian epidermis harbors the so-called Langerhans cells (LC)2 as a third cell population, which is thought to participate in immune reactions involving the epidermis (1, 2). LC are dendritic cells located above the basal cell layer, have a characteristic ultrastructural appearance (3), and originate from a bone marrow precursor (4, 5). They lack membrane-incorporated surface immunoglobulin and sheep red blood cell receptors, but are the only epidermal cells (EC) that bear receptors for the Fc portion of IgG (Fc-IgG) and for C3 and express Ia antigens (1, 2). Because LC constitute only 3 to 5% of all EC, enrichment procedures are important for functional studies. Moderate enrichment of LC to 18 to 35% by separation of Fc-IgG rosetting EC on density gradients was sufficient to show the critical role of LC in EC-induced T cell proliferation (6). More powerful isolation procedures are needed, however, for more exacting analysis of LC functions, such as their role in immune induction, their secretory capacities including production of EC-derived thymocyte-activating factor (7, 8) and prostaglandins, immune endocytosis, the role of LC granules, etc. Methods hitherto available for enriching LC beyond 60% (9, 10) are time consuming and of low yield and viability, and thus are of limited practical value. In this report we describe a simple and efficient procedure to obtain viable LC suspensions of high purity based on the use of monolayers of protein A-bearing Staphylococcus aureus cells as a solid-phase immunoadsorbent (11).