Neutrophil apoptosis induced by E coli alone orE coli in combination with 40 μg/mL of IAV. The degree of apoptosis induced by E coli alone or E coli in combination with 40 μg/mL of IAV after 6 (A) or 24 (B) hours of incubation are shown. Results are expressed as percentage of cells with hypodyploid DNA and represent the mean ± SEM of three separate experiments. At 24 hours all concentrations of E coli alone caused significantly more apoptosis than control buffer (P ≤ .05). (*)Indicates where the combination of E coli and IAV caused significantly greater apoptosis than E coli alone. (**)Indicates where the combination of E coliand IAV caused significantly greater apoptosis than either E coli or IAV alone.