Human neutrophils activated by interferon-gamma and tumour necrosis factor-alpha kill Entamoeba histolytica trophozoites in vitro

The interaction between cytokine-activated human neutrophils and Entamoeba histolytica trophozoites was studied as well as the mechanism(s) involved. Treatment of neutrophils with rIFN-gamma alone allowed them to kill 30% of E. histolytica trophozoites; however, rIFN-gamma and rTNF-alpha pretreatments in combination increased neutrophil killing to 70%. In the absence of direct contact between neutrophils and amebae, rIFN-gamma-treated neutrophils were shown to kill 70% of amebae, and rIFN-gamma- and rTNF-alpha-treated neutrophils killed 97% of amebae. Neutrophil enhancement of amebicidal activity following cytokine treatments was correlated with increased neutrophil resistance to amebic contact-dependent killing and was shown to be 73% H2O2 dependent.