PRESENCE OF A TETRAHYMENA GROWTH-PROMOTING ACTIVITY IN FETAL BOVINE SERUM

Treatment of cultures of the ciliate Tetrahymena with fetal bovine ser um (FBS) enhanced the rate of cell proliferation. The growth promoting activity was partially purified from FBS as a high Mr complex includi ng four components with apparent Mr values of 180 kDa, 68 kDa, 60 kDa and 30 kDa by a 4-step procedure. The 180 kDa component was identified by amino acid sequencing as alpha 2-macroglobulin. The addition of pu rified alpha 2-macroglobulin from bovine plasma to cultures of Tetrahy mena was also found to enhance the rate of cell proliferation. This re port is the first dealing with the direct identification of a mammalia n factor which promotes the growth of free-living protozoa.