In vitro growth of murine T cells. III. Method for separation of T cell growth factor (TCGF) from concanavalin A and biological activity of the resulting TCGF

T cell growth factor (TCGF) resulting from the incubation of murine splenocytes with concanavalin A (Con A) has been partially purified and separated from Con A. Sequential application of 50-70% saturated ammonium sulfate precipitation and G-100 gel filtration chromatography has resulted in a 300-fold purification of TCGF with a 60% yield. 99.99% of Con A has been removed from the TCGF by these steps. TCGF exists in two molecular weight forms of about 50,000 and 25,000 daltons. TCGF activity is degradable by trypsin digestion and is stable at 56°C for 30 min, but is inactivated by heating at 80°C. Lymphoid cells activated by either Con A or allogeneic in vitro sensitization will grow in TCGF free of Con A but fresh splenocytes will not grown in the absence of Con A, implying a need for prior activation before TCGF sustained growth of T cells can be achieved.