Brief Communication Commercial Pha Preparations Contain Different Mitogenic Components

Three commercially available purified phytohaemagglutinin (PHA) preparations have been examined both chemically and biologically. Marked differences were observed in both composition and mitogenic effect on lymphocytes; the existence of at least two distinct mitogenic fractions in PHA was confirmed. A number of commercial preparations of PHA have become available for use as mitogens in lymphocyte cultures. Since there is no cross-standardization of biological activity between these preparations, workers have used their own discretion about which to use and whether further purification is desirable. Three commercial purified PHA preparations have been examined, and marked biological and chemical differences have been found.