The present report deals with the behaviour of mast cells in mice in the course of Entamoeba histolytica infection by the strains. Mice weighing about l6 gm were used for three experimental groups; control, sham infection and experimental. The experimental group was infected with Entamoeba histolytica trophozoites directly into cecum by laparotomy. Strains isolated from three hepatic amoebic abscess cases were used. Mesenteric samples from the region of terminal ileum were fixed in methyl alcohol and stained with Pugh's solution. The ulcers in cecum were examined. Changes in number and structure of mesenteric mast cells and blood eosinophils were as follows. The number of mast cell in mesenteric tissues of the infected group increased from first day of the infection and persisted up to 34th day of the observation period. Degranulation and disruption of mast cells increased in the infected group compared with groups of the sham operation and the contro1, but showed no difference by the strains of Entamoeba histolytica. The blood eosinophilia was observed in the infected group and persisted until the observation period. Ulcers in cecum were found in all the infected groups. The results above indicate that mast cells are keenly related with the course of Entamoeba histolytica infection.
