Increased leucocyte histamine release by Entamoeba histolytica antigen in patients with amoebic abscess of the liver

Leucocytes (basophils) from non-atopic adult subjects living in an area highly endemic with Entamoeba histolytica release histamine in a dose-dependent fashion upon in vitro exposure to an antigen of axenically grown E. histolytica (histolyticin). Leucocytes of patients with acute amoebic liver abscess were significantly more sensitive to this antigen than leucocytes of control subjects, including patients that had recovered from amoebic liver abscess. By comparison Concanavalin-A induced histamine release found in patients with amoebic liver abscess and healthy controls suggest an immunological mechanism for histolyticin induced in vitro histamine release. This is also suggested by the inability of histolyticin to release histamine from leucocytes of healthy newborn infants and the significant fall in sensitivity to histolyticin following incubation of leucocytes in acid pH. Histamine and other mediators may contribute locally to the early intense inflammatory reaction observed in tissue invasion by E. histolytica.