Mouse Strain Differences in Plasmacytoid Dendritic Cell Frequency and Function Revealed by a Novel Monoclonal Antibody

Abstract

We report in this study the generation of a novel rat mAb that recognizes mouse plasmacytoid dendritic cells (pDC). This Ab, named 120G8, stains a small subset of CD11c^low spleen cell with high specificity. This population produces high amounts of IFN-α upon in vitro viral stimulation. Both ex vivo- and in vitro-derived 120G8⁺ cells display a phenotype identical with that of the previously described mouse pDC (B220^highLy6C^highGr1^lowCD11b⁻CD11c^low). Mice treated with 120G8 mAb are depleted of B220^highLy6C^highCD11c^low cells and have a much-reduced ability to produce IFN-α in response to in vivo CpG stimulation. The mAb 120G8 stains all and only B220^highLy6C^highCD11c^low pDC in all lymphoid organs. Immunohistochemical studies performed with this mAb indicate that pDC are located in the T cell area of spleen, lymph nodes, and Peyer’s patches. Although the Ag recognized by 120G8 is not yet known, we show that its expression is up-regulated by type I IFN on B cells and DC. Using this mAb in immunofluorescence studies demonstrates strain- and organ-specific differences in the frequency of pDC and other DC subsets. 129Sv mice have a much higher frequency of pDC, together with a lower frequency of conventional CD8α⁺CD11c^high DC, compared with C57BL/6 mice, both in spleen and blood. The higher ability of 129Sv mice to produce IFN-α in vivo is related to a higher number of pDC, but also to a higher ability of pDC from 129Sv mice to produce IFN-α in vitro in response to viral stimulation.