An assay for the mitogenic activity of phytohemagglutinin preparations.

By Douci &ss C. TORMEY AND GERALD C. MUELLER T HE ADDITION of phytohemagglutinin, an extract of the kidney bean Phaseolus vulgaris, to cultures of human peripheral lymphocytes promotes the synthesis of v-globulin, ribonucleic acid (RNA), and desoxyribonucleic acid (DNA), and induces mitosis in a large fraction of lymphocytes.1’7 The present communication describes an assay in which the graded induction of DNA synthesis in leukocyte cultures by different levels of phytohemagglutinin has been used to measure this mitogenic principle quantitatively. In addition to its usefulness in isolating the mitogenic principle, the assay also affords a system for the demonstration and study of factors present in normal and pathologic sera that modify the ability of leukocytes to undergo replication.