Observations on Antigens for Complement Fixation in Amebiasis. ∗

Abstract

Since the publication of the technique of the complement fixation test for amebiasis devised by the senior author (Craig) 1 , in which absolute alcoholic extracts of cultures of Endamoeba histolytica were employed as antigens, several modifications of the test have been published and other antigenic extracts have been described.

Menendez 2 and Spector 3 employed simple alcoholic extracts of cultures of E. histolytica as antigens with satisfactory results, and Menendez stated that a simple suspension of cultures of E. histolytica in formalinized saline also possessed good antigenic properties. Sherwood and Heathman 4 and Heathman 5 used antigens prepared by extracting the dried sediment of cultures of E. histolytica, rich in the amebæ, with ether, 96% alcohol and acetone, after which cholesterin was added in different amounts, and found that such antigens were efficient. Tsuchiya 6 and Weiss and Arnold 7 successfully employed absolute alcohol extracts of cultures of E. histolytica in their modifications of this complement fixation test. With all of these antigenic extracts these observers obtained a high percentage of positive results in infections with E. histolytica and negative results in other infections or diseases and in healthy individuals, thus amply confirming the specificity of the test.

We have recently endeavored to obtain more easily prepared antigens by extracting the mucoid material which may be readily obtained from the intestine of dogs suffering from acute amebic dysentery experimentally produced. Such material is usually very rich in amebæ and contains very few bacteria as compared with cultures of this parasite. The utilization of this material as a source of antigen for the complement fixation test was first suggested by our assistant, Dr. Edwin S. Kagy, and it has been found that extracts prepared from it are suitable for use as antigen and are sometimes stronger in antigenic properties than the absolute alcohol extracts of cultures of E. histolytica.