Mouse IgE response to an allergen from Entamoeba histolytica.

Attempts were made to demonstrate the presence of allergenic components in an extract of axenically cultured Entamoeba histolytica (HK 9). Various strains of mice were immunized i.p. with a low dose of the extract mixed with AI(OH)3 and boosted with the same mixture 4 wk later. A high titer of IgE antibody response was demonstrated in BALB/c, DBA/2 (H-2d), CBA (H-2k), and SWM strains but not in C3H/He (H-2k) strain. The extract was fractionated by gel filtration with Sephadex G-200 and then by DEAE-cellulose chromatography with a gradient buffer with progressive increase in molarity. Fractions having the strongest activity to stimulate the IgE antibody response in the mouse were subjected to SDS polyacrylamide gel electrophoresis. From the results of gel filtration and polyacrylamide gel electropho- resis, the molecular weight of the partially purified allergen was estimated to be 25,000 to 27,000 daltons.