Differential regulation of C-type lectin expression on tolerogenic dendritic cell subsets.

Antigen presenting cells (APC) express high levels of C-type lectins, which play a major role in cellular interactions as well as pathogen recognition and antigen presentation. The C-type lectin macrophage galactose-type lectin (MGL), expressed by dendritic cells (DC) and macrophages, mediates binding to glycoproteins and lipids that contain terminal GalNAc moieties. To investigate MGL expression patterns in more detail, we generated two new monoclonal antibodies and set up a quantitative real-time PCR analysis to determine MGL mRNA levels. MGL is not expressed by blood-resident plasmacytoid DC and thus represents an exclusive marker for myeloid-type APC. Dexamethasone treatment upregulated MGL expression on DC both at the protein and mRNA level in a time- and dose-dependent manner. In contrast, DC generated in the presence of IL-10 did not display enhanced MGL levels. Furthermore, dexamethasone and IL-10 also differentially regulated expression of other C-type lectins, such as DC-SIGN and Mannose Receptor. Our results demonstrate that depending on the local microenvironment, DC can adopt different C-type lectin profiles, which could have major influences on cell-cell interactions, antigen uptake and presentation.