Nondialyzable substances capable of inhibiting anti-A, anti-B and anti-H(O) specific blood-group agglutinins have been found in higher and lower plants. In higher plants, they were encountered almost regularly and nearly exclusively in the Gymnospermae. Partial purification showed the active principle to be in the carbohydrate fraction and practically free of nitrogen.Bacteria grown on completely synthetic media usually contained the most potent material in their somatic carbohydrate antigens but often were found to be active as such.Specific action was exhibited by Taxus twig extracts, the purest fraction of which was considerably more active against eel anti-H(O) serum than any known mammalian blood-group mucoid. Escherichia coli 086 exhibited high and E. coli 026 moderate B activity exclusively and Salmonella poona and S. atlanta neutralized eel anti-H(O) serum only while a strain of Escherichia freundii inhibited anti-A sera only. Many other preparations were less specific and neutralized antibodies against blood group A, B and H(O). The exact mode of action of these latter substances will have to be established individually.Several of these serologic blood-group active materials, some of them essentially physicochemically homogeneous, possess other biologic activities as well. There is indication that at least those substances from plants which are disproportional in their action bear an immunologic relationship to mammalian blood-groups mucoids. The possible significance of these findings especially for the problem of “natural iso-antibodies” has been mentioned.
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