Frontiers in Immunology (Jan 2016)
Redefining myeloid cell subsets in murine spleen
Abstract
Spleen is known to contain multiple dendritic and myeloid cell subsets, distinguishable on the basis of phenotype, function and anatomical location. As a result of recent intensive flow cytometric analyses, splenic DC subsets are now better characterized than other myeloid subsets. In order to identify and fully characterize a novel splenic subset termed ‘L-DC’ in relation to other myeloid cells, it was necessary to investigate myeloid subsets in more detail. In terms of cell surface phenotype, L-DC were initially characterized as a CD11bhiCD11cloMHCII-Ly6C-Ly6G- subset in murine spleen. Their expression of CD43, lack of MHCII, and a low level of CD11c was shown to best differentiate L-DC by phenotype from conventional DC subsets. A complete analysis of all subsets in spleen led to the classification of CD11bhiCD11cloMHCII-Ly6CloLy6G- cells as monocytes, expressing CX3CR1, CD43 and CD115. Siglec-F expression was used to identify a specific eosinophil population, distinguishable from both Ly6Clo and Ly6Chi monocytes and other DC subsets. L-DC were characterized as a clear subset of CD11bhiCD11cloMHCII-Ly6C-Ly6G- cells which are CD43+, Siglec-F- and CD115-. Changes in the prevalence of L-DC compared to other subsets in spleens of mutant mice confirmed the phenotypic distinction between L-DC, cDC and monocyte subsets. L-DC development in vivo was shown to occur independently of the BATF3 transcription factor that regulates cDC development, and also independently of the FLT3L and GM-CSF growth factors which drive cDC and monocyte development, so distinguishing L-DC from these commonly defined cell types.
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