TLR expression in immunocompetent cells. (A) Resting B cells and GC B cells were purified from total tonsillar B lymphocytes. Total RNA was prepared and subjected to Northern analysis employing radiolabeled probes complementary to TLR1-10. Specific TLR transcripts are indicated by an arrow. The bottom panels show the ribosomal 28S and 18S subunits as seen under UV after staining with ethidium bromide. PMNs, dendritic cells, and monocytes are included as positive controls for TLR1-8 expression. Monocytes are included as a negative control for TLR9 and TLR10, which among the cell types tested, show highest expression in B cells. (B) Fresh human leukocyte subpopulations were separated and cultured in vitro in the absence or presence of the indicated stimuli for 3 hours. Total RNA was prepared and subjected to Northern analysis. Specific TLR transcripts are indicated by an arrow. The side panels show the ribosomal 28s and 18s subunits as seen under UV after staining with ethidium bromide. Results are representative of 3 independent experiments.