Human monocytes transcribe IFN-β more rapidly than nonmyeloid cell types. (A) Primary monocytes were exposed to LPS, Pam3CSK4, or Sendai virus for 0, 1, 2, 3, and 6 hours. The level of IFN-β mRNA was measured by semiquantitative reverse transcription PCR. (B) The kinetics of IFN-β mRNA expression in pathogen-stimulated primary monocytes. Monocytes were exposed to LPS (blue), Sendai virus (green), or Pam3CSK4 (red). The level of IFN-β mRNA was then measured by real-time PCR. (C) Primary monocytes, and nonmyeloid HeLa and HEK293 cells were exposed to Sendai virus for 0, 1, 2, 3, 6, and 9 hours. The level of IFN-β mRNA was measured by semiquantitative reverse transcription PCR. (D) The kinetics of IFN-β mRNA expression in Sendai virus-exposed primary monocytes (red), HeLa cells (green), and HEK293 cells (blue). The level of IFN-β mRNA was then measured by real-time PCR. (E) Primary monocytes and HEK293 cells were stimulated by Sendai virus. The supernatants were tested by enzyme-linked immunosorbent assay for IFN-β production. (A-E) Similar results were obtained in 3 independent experiments with monocytes from 3 different donors, one of which is shown.