The low-affinity receptor for IgE, FcepsilonRII (CD 23), plays an important role in IgE-mediated disorders such as allergy, atopy, and parasitic infections. In humans, the FcepsilonRII B isoform on epidermal Langerhans cells is thought to be an important accessory molecule in the allergy-specific T cell activation in atopic dermatitis. Since considerable knowledge about the accessory function of Langerhans cells for T-cell activation stems from mouse models, and since an IgE-bearing Langerhans cell mouse model would be useful in studying the pathophysiology of atopic dermatitis, we determined whether FcepsilonRII was also present on murine Langerhans cells. FcepsilonRIIa, which is the major FcepsilonRII isoform in mice, was found to be constitutively expressed on spleen cells from normal mice but was not present on epidermal Langerhans cells. When interleukin-4, a known inducer of FcepsilonRII, was administered in vivo, FcepsilonRII-specific mRNA and protein was significantly unregulated in spleen cells but not in Langerhans cells. De novo synthesis of FcepsilonRII was also induced in vitro by interleukin-4 on spleen cells, but not on epidermal cells. The presence of a recently cloned murine counterpart of the human Fc-epsilon- R. II isoform on murine Langerhans cells could also be excluded on the protein and mRNA level because of the high degree of homology to mouse Fc-epsilon-R IIA. Taken together the data indicate that murine epidermal Langerhans cells do not express the low-affinity receptor for IgE.