Cathepsin E in antigen-presenting Langerhans and interdigitating reticulum cells. Its possible role in antigen processing.

A specific rabbit anti-human cathepsin E serum detected this aspartic proteinase in Langerhans cells of the skin, in interdigitating reticulum cells of lymph nodes and spleen and in histiocytosis X cells, but not in macrophages. Immunoblotting of tissue extracts confirmed the presence of cathepsin E in skin and lymph nodes. Electron immunocytochemistry with the protein A gold technique localized cathepsin E in the endoplasmic reticulum and in endosomal vesicles of both interdigitating and Langerhans cells, likely involving Birbeck bodies. A role of endosomal cathepsin E in antigen processing is suggested.