Analysis of cell numbers (Fig. 1c) revealed that cultures treated with LPS or CpG ODN had a greater number of total cells present after 6 days than were present in control cultures. By contrast, cultures selleck inhibitor to which Poly I or Poly I:C had been added showed reduced cell numbers. The increase in cell numbers induced by LPS and CpG ODN could mainly be attributed to a significant increase in the number of cells expressing a CD11clo/MHCIIlo phenotype

(Fig. 1c), while the number of these cells present in cultures stimulated with influenza virus, Poly I or Poly I:C was reduced in comparison to unstimulated cultures (Fig. 1c). Therefore, we suggest that the reduction in cell numbers observed in response to influenza virus, Poly I or Poly I:C was caused by reduced BMDC production, whereas the increased cell number observed in response to LPS or CpG ODN was caused by the production of cells other than BMDCs. To characterize the cells generated in response PS-341 mw to stimulation of bone marrow cultures with influenza viruses or TLR ligands, bone marrow cells were cultured in the presence of GM-CSF, with or without stimulation, for 6 days and the cellular morphology was assessed

by staining cells with haematoxylin and eosin. Differential counts were performed to assess the cell populations present. The results presented in Fig. 2 show that cells grown in the presence of GM-CSF alone were predominantly (50–60%) large cells displaying the described morphology of DCs. The proportion of cells of this type was clearly reduced with all tested stimuli. However, the predominant cell types produced depended on the nature of the added stimulus. In cultures treated with influenza viruses, Poly of I or Poly I:C there was a marked increase in the number of cells with a neutrophil-like morphology (Fig. 2a). Conversely, in the presence of LPS or CpG ODN, most of the cells generated

displayed a lymphoid morphology (Fig. 2b). Differential counts (Fig. 2c) clearly showed this change in the type of cells generated. The lymphoid appearance of cells generated in cultures containing LPS or CpG ODN suggested that they could belong to the B lineage, or might possibly be plasmacytoid DCs (pDCs). To explore the possibility of these cells belonging to the B lineage, we analysed the expression of the B-lineage marker CD19. The resulting data (Fig. 2d) showed that CD19 was not expressed by the cells generated under these conditions, excluding the possibility that they belong to the B-cell lineage. pDCs are reported to have a morphology similar to that of lymphocytes and have been found to have a CD11clo/CD11b−/MHCIIlo/B220+/Gr1+ phenotype.15 We therefore examined the expression of these markers using flow cytometry. The data (Fig. 2e) showed that, as described above, cells generated in cultures containing LPS or CpG ODN predominantly express low levels of CD11c and MHCII.