CXCL8 and infection: Notably, however, these levels were modest compared with the potent stimulation attributable to the Cag T4SS, which in this study were found to be ~6x higher following infection with the AB5 wildtype (cag+) strain (mean IL-8 concentrations of 3853 pg/mL vs 658 pg/mL for wildtype and cagE mutant respectively).