Heterogeneity of freshly isolated human tonsil dendritic cells demonstrated by intracellular markers, phagocytosis, and membrane dye transfer

Abstract

Background Heterogeneity within human dendritic cells (DCs) has been described but its functional relationships to cells of macrophage lineage and its role in human immunodeficiency virus (HIV) infection in vivo remain unclear. Methods Tonsil macrophages and DCs were isolated from low‐density cells by negative selection and DCs were sorted into myeloid and plasmacytoid populations using antibodies to CD11c or CD123. Phagocytosis of latex beads and uptake of dye‐labeled target cells were compared by flow cytometry and CD68 and S‐100 by immunofluorescence on cytospins of sorted cells. Results Bead uptake and membrane dye transfer were found in both blood and tonsil CD11c+ DCs and in CD14+ cells particularly from blood monocytes. CD11c‐ DCs were poorly phagocytic but took up fluorescent dye from intact, necrotic or apoptotic cells. Tonsil DCs and macrophages expressed both CD68 and S‐100 but CD11c‐ DCs expressed CD68 only. Conclusions Freshly isolated CD11c+ tonsil DCs are similar to CD14+ macrophages in phagocytic function but the poorly phagocytic CD11c‐ DCs can also take up membrane from target cells. The intracellular markers commonly used to identify DCs and macrophages in situ do not identify accurately the CD11c‐ DC subset nor do they distinguish tonsil macrophages from DCs. Cytometry 48:167–176, 2002. © 2002 Wiley‐Liss, Inc.

Human Plasmacytoid Dendritic Cells Phagocytose, Process, and Present Exogenous Particulate Antigen

“…In this study, we investigated whether pDCs can play a role in immune responses against exogenous particulates. Up to now, it was highly controversial whether pDCs are able to respond to stimuli entrapped in particle-like structures (3,8,9,14,(16)(17)(18)(19). We demonstrate that pDCs are clearly capable of phagocytosing Ag entrapped within PLGA microparticles and subsequent processing of the encapsulated Ag.…”

“…Although some studies show that pDCs phagocytose apoptotic cells (16,17), several report that pDCs hardly take up particulates, such as apoptotic cells (18), latex beads (17,19), zymosan granules (14), or extracellular bacteria (3). Human pDCs have been shown to prime functional T cell responses on phagocytosis of apoptotic debris (16).…”

Examination of the Reticular Epithelium of the Bovine Pharyngeal Tonsil

“…Unlike human adenoids, substantial CD14 immunoreactivity was present in bovine pharyngeal mucosal epithelial cells. Immunoreactivity to CD14 has been previously documented in bovine palatine tonsilar epithelium, lymphocytes and plasma cells of human adenoid submucosa, and human tonsilar macrophages (Stent et al, 2002;Palmer et al, 2009). Multifocally intense immunoreactivity to CD14 in the present study may be due to the PRR nature of the CD14 receptor and constant exposure of the tonsils to microbial agents and their products.…”

“…CD68 is another marker associated with human and bovine macrophages and multinucleated giant cells (Ackermann et al, 1994;Stent et al, 2002;Palmer et al, 2009;Ben-Yaakov et al, 2011). In contrast to CD14, immunoreactivity for CD68 was noted among cells scattered within follicular and interfollicular regions with few CD68þ cells within either reticular or nonreticular epithelium.…”

Recognition of single-stranded RNA viruses by Toll-like receptor 7

“…By rapidly producing high levels of type I IFNs, pDCs rarely become infected with viruses taken up through the endocytic pathways. Unlike myeloid cells, pDCs do not possess efficient phagocytic abilities to take up large particles or apoptotic cells (36). Thus, the details of viral uptake and intracellular processing by the pDCs resulting in their potent antiviral functions will require further investigation.…”