Monoclonal antibodies to human epidermal filaggrin, some not recognizing profilaggrin

To improve understanding of human profilaggrin processing to filaggrin, we produced seven monoclonal antibodies against epidermal filaggrin (AHF1-7). They were characterized on human epidermis by indirect immunofluorescence, immunogold labeling, and immunoblotting and found to be directed against seven different epitopes of (pro)filaggrin. AHF1-5 labeled the keratohyalin granules and the fibrous matrix of the lower corneocytes, and recognized filaggrin and profilaggrin. AHF6 also labeled the keratohyalin granules and the corneocyte matrix, but only recognized filaggrin. In addition to this reactivity within the upper epidermis, AHF4-6 stained the cytoplasm of the basal cells, and cross-reactivity of AHF5 and AHF6 with cytokeratin K14 was revealed on immunoblots. It is interesting that AHF7 recognized filaggrin, but not profilaggrin, and labeled only the corneocyte matrix and not the keratohyalin granules. This indicates that filaggrin and cytokeratins share several antigenic determinants and that filaggrin bears at least one epitope absent from its precursor. The original series of monoclonal antibodies described here appears to be a powerful tool for studying human profilaggrin processing in normal conditions and in the keratinization disorders in which processing is altered.