Differences in complement-mediated killing of Entamoeba histolytica between men and women--an explanation for the increased susceptibility of men to invasive amebiasis?

Men are more than 7 times more likely to develop amebic liver abscess or amebic dysentery caused by Entamoeba histolytica than women. Because the complement system could play a key role in controlling amebiasis, we determined whether serum from men and women differ in the ability to kill amebic trophozoites. We found that serum from women was significantly more effective in killing E. histolytica trophozoites than serum from men, and this killing was complement dependent. Our results provide a possible explanation for the differential susceptibility of men and women to amebic liver abscess and amebic colitis.