FIG. 4.

Levels of enterocyte apoptosis in human duodenal epithelial monolayers incubated with either 5% DMEM growth media alone (◊) (n = 15 at 24 h, n = 9 at 48 h), G. lamblia NF in 5% DMEM (□) (n = 9 to 15), strain S2 sonicates (○) (n = 9 to 15), strain WB sonicates (×) (n = 3), strain PB sonicates (+) (n = 3), or 20 μg of camptothecin/ml (▵) (n = 6). Apoptotic ratios were also calculated for monolayers pretreated with Z-DEVD-FMK followed by incubation with G. lamblia NF (▪) (n = 6 at 24 h, n = 6 at 48 h) or S2 sonicates (•) (n = 6 at 24 h, n = 6 at 48 h). Values after 30 min of ELISA development were calculated as absorbance ratios versus values measured in control monolayers (arbitrarily set at 1.0) (◊). NF and S2 isolates increased the production of apoptotic nucleosomes to levels induced by proapoptotic camptothecin and to levels greater than those in negative controls, whereas WB and PB isolates did not. Pretreatment with Z-DEVD-FMK prevented the induction of apoptosis by NF and S2 isolates. Values are means ± standard errors of the means. ∗, P < 0.05 for NF versus control; =, P < 0.05 for S2 versus control; #, P < 0.05 versus control.