Monocytes, freshly isolated or matured in vitro with M-CSF, express CXCL13 mRNA after LPS stimulation. (A) RT-PCR analysis of freshly isolated monocytes (top panel) and monocytes cultured for 3 days with either M-CSF (middle panel) or IL-4 and GM-CSF (bottom panel). Cells were stimulated with LPS (100 ng/mL) before total RNA was isolated at different time points after stimulation as indicated (2-48 hours). Representative results from 3 independent experiments are displayed in comparison with the expression levels of the “housekeeping” gene GAPDH in the same cultures. (B-C) Immunofluorescence staining of freshly isolated monocytes (B) and monocytes matured in vitro for 3 days with M-CSF (C). After 24 hours of LPS stimulation, the cells were stained for the markers indicated (merged color separations; see keys). Bars represent 20 μm.