Haemagglutinating, Precipitating and Lymphocyte-stimulating Factors of Phytohaemagglutinin

Abstract

EXTRACTS from certain seeds of the Leguminosae are known to possess interesting biological properties. An extract of Phaseola vulgaris, phytohaemagglutinin (PHA), agglutinates red and white blood cells^1,2 and tumour cells³, and indiscriminately stimulates blood lymphocytes cultured in vitro to undergo blastic transformation and increased mitogenic activity⁴. Since lymphocytes of a sensitized donor are known to be stimulated in the same manner when exposed to a previously encountered antigen^5,6, the possibility of PHA being a universal antigen has been considered⁷. Recently it has been noted by ourselves and others^8,9 that PHA likewise forms a precipitate indiscriminately with serum. Our demonstration of this ability of PHA to form a precipitin line with human serum and numerous animal sera appeared to support the concept of its being a ubiquitous antigen. If this were a valid concept, however, treatment of PHA to remove its precipitating activity would entail loss of antigenicity and might be expected to impair the lymphocyte-stimulating factor as well.