SYK and infection: To determine the dose-dependent effects of Syk inhibition, we added Syk inhibitors BAY (0.1, 0.5, 1.0 μM), PIC (5, 25, 50 μM), or R406 (0.5, 2.5, 5.0 μM) 30 min prior to infection with O. tsutsugamushi and assessed CLR gene transcription via qRT-PCR Western blot or at 6 h post-infection (hpi).