A complement fixing antigen, specific for the diagnosis of schistosomiasis, was isolated from adult Schistosoma mansoni. Following an initial extraction with sodium desoxycholate solution, the antigen was fractionated by ethanol under conditions of carefully controlled pH and ionic strength, and finally precipitated by calcium. The antigen was evaluated in a quantitatively standardized complement fixation test to determine its sensitivity and specificity, and was found to be more specific for the diagnosis of schistosomiasis than antigens isolated by other methods.
Qualitative and quantitative chemical analyses of the antigen showed the structural components to be protein and lipid, combined in the approximate ratio of 2.5:1. Attempts were made to relate the physicohemical properties of the antigen to its structure.