Expression of an epitope as detected by the novel monoclonal antibody 4F7 on dermal and epidermal dendritic cells. I. Identification and characterization of the 4F7+ dendritic cell in situ

Abstract

Ears of Balb/c mice were treated epicutaneously with 0.5% 2,4-dinitrofluorobenzene (DNFB) to obtain monoclonal antibodies characterizing molecules on epidermal dendritic cells that are involved in the induction and elicitation of allergic contact dermatitis. Six hours after this treatment, epidermal cells were prepared from the ear skin, and Ia-positive cells were enriched by indirect panning and injected into rats. Hybridomas were generated and supernatants were screened for antibodies on ear skin from DNFB-treated and untreated animals. A clone (4F7) was isolated and characterized by immunohistochemistry and immunoelectron microscopy on murine skin and other organs. The monoclonal antibody 4F7 (IgG1) recognized distinct dendritic cells in the dermis and very few dendritic cells in the paracortical area of the lymph nodes, the white pulp of the spleen, and the mucosa of the large intestine in normal animals. By fluorescence activated cell sorter analysis, it stained about 1.64% of the dermal and no epidermal cells in the skin of untreated animals. Approximately 50% of the dermal 4F7+ cells expressed Ia molecules on their surface. Six hours after application of 0.5% DNFB, the expression of the 4F7 antigen was strongly enhanced in vivo on dendritic cells in both the dermis and epidermis. About 15% of the epidermal dendritic cells expressing 4F7 exhibited Birbeck granules, the other Birbeck granule-negative cells resembled indeterminate dendritic cells (IDCs). The dermal and epidermal 4F7+ cells could be highly (98%) enriched with 4F7-labeled immunomagnetic particles. Transmission electron microscopic analysis of such preparations showed typical characteristics of dendritic cells with 50% or 100%, respectively, of these cells expressing Ia molecules on their cell membrane. The results suggest that the 4F7 epitope is expressed on dendritic cells related to Langerhans cells and is upregulated by an inflammatory stimulus.