Monoclonal Antibody EBM11 (Anti-CD68) Discriminates between Dendritic Cells and Macrophages after Short-Term Culture

Abstract

Identification of dendritic cells (DC) is usually done on the basis of their strong MHC class II expression, their typical dendritic morphology and their capacity to induce a strong proliferation of allogeneic T cells. However using these criteria DC can easily be confused with MHC class II positive macrophages (MΦ). In addition, the lack of an antibody directed to a specific DC marker greatly hampers the discrimination between DC and MΦ. In the present study it is shown that EBM11 (anti-CD68) is a marker specific for both human MΦ and DC but in a distinctive way. Human DC locate the EBM11 reactivity in a discrete juxtanuclear spot in contrast to MΦ which show EBM11 reactivity throughout the cytoplasm. This greatly improves identification of DC. Light and electron microscopy showed that the CD68 epitope is associated with (phago-)lysosomes. Remarkably the EBM11 spot was only seen in DC after short-term culture, which is an essential step in all classical DC enrichment procedures. Before culture, MΦ and DC were indistinguishable. These results show the close relationship between MΦ and DC and suggest an important role for the structure of the lysosomal apparatus in these antigen-presenting cells. © 1991, Gustav Fischer Verlag · Stuttgart · New York. All rights reserved.