BTC and escherichia coli infection: We next performed quantitative real-time PCR to investigate whether expressions of the above-mentioned ligands are affected in response to meningitic E. coli. We selected six ligands, EGF, AREG, BTC, EREG, HB-EGF, and TGFα, representing the EGFR-related ligands previously examined in a study with N. gonorrhoeae, and determined their transcriptional levels in response to meningitic E. coli infection.