Two allergenic substances (C5 and P4), which consisted of ribonucleic acid as their main component, were isolated from the heated extract of liver fluke
(Fasciola hepatica) by means of precipitation by ammonium sulphate and phenol extraction, followed by extraction with potassium acetate and ethanol fractionation.
One of these substances, C5, which was extracted with phenol was electrophoretically homogeneous, but ultracentrifugally was shown to contain one other substance in a small quantity.
The other substance, P4, which was isolated from the phenol insoluble fraction was electrophoretically and ultracentrifugally homogeneous.
Both of these were almost the same in biological activity, and their solutions, which were diluted 1: 100, 000 with Ringer's solution, were still active in the intradermal reaction to the fascioliasis of cattle. Judging from their activity and yield, it seems that all the allergenic substances which are in the heated extract of liver fluke, are represented by the protein allergen reported already, as well as by C5 and P4 described here.
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