Fc epsilon RI mediates IgE binding to human epidermal Langerhans cells

In a recent series of experiments, we observed that epidermal Langerhans cells (LC) of healthy, non-atopic individuals have the capacity of specifically binding monomeric serum or myeloma IgE. IgE-binding to LC could neither be prevented by pre-incubation of the cryostat sections with monoclonal antibodies (MoAb) against either Fc epsilon RII/CD23 or Fc gamma RII/CD32 nor by the addition of excess amounts of lactose, but could be entirely abrogated by pre-incubation with the anti-Fc epsilon RI MoAb 15-1. A direct testing of the anti-Fc epsilon RI MoAb 15-1 and 19-1 on cryostat sections in an indirect immuno-double-labeling technique showed that, in contrast to eight different anti-Fc epsilon RII/CD23 MoAb, these MoAb react with the majority of CD1a-bearing epidermal cells. At an ultrastructural level, 15-1 immunogold-labeling in the epidermis was confined to the surface of cells exhibiting Birbeck granules. In further experiments, we were able to amplify by polymerase chain reaction (PCR) technology transcripts for the alpha, beta, and gamma chains of Fc epsilon RI from LC-enriched epidermal cells and dermal cells, but not from LC-depleted epidermal cells. Transcripts for the mast cell enzyme tryptase were exclusively found in dermal cell-derived RNA preparations, thus excluding a contamination of the LC-enriched epidermal cell preparations by dermal mast cells. Collectively, these data show that epidermal LC, but not other epidermal cells, express Fc epsilon RI molecules.