ABSTRACT
We used an indirect haemagglutination test with Giardia lamblia trophozoites as the antigen to detect anti-Giardia lamblia antibodies in serum, the soluble tritonated Giardia lamblia antigen being used for detecting anti-giardial antibodies in sera of 60 human subjects. Titers in some of these subjects were 1 : 80-1 : 2560. whereas titers in some subjects were negative button to 1 : 20. The results indicated that Giardia lamblia, an intestinal parasite, induced a systemic antibody response and the indirect haemagglu tination test for anti-Giardia lamblia antibodies is a simple specific and reproducible system which may be useful in epidemiologic and immunologic studies of giardiasis. The specificity of the anti-bodies was demonstrated by the ability of live Giardia lamblia trophozoites, but not Entamoeba histolytica to absorb the antibody activity.