Generation of T Memory Cells in One‐Way Mixed Lymphocyte Culture

CBA lymphocytes were primed m one‐way mixed lymphocyte culture by DBA/2 under conditions where only T cells proliferate, and the blast cells were recovered on the sixth culture day by fractionation in 1 ‐g velocity sedimentation When placed on a syngeneic (to responder cells) feeder layer, the blasts reverted to lymphocytes (‘secondary lymphocytes’) Two functions, dissimilar from nonprimed T cells, were defined for the secondary lymphocytes: they were cytotoxic to relevant allogeneic target cells in vitro, and they responded promptly to the original stimulator cells in secondary mixed lymphocyte culture These properties were then used to define the rate of recovery of the activated cells in the blast fraction CBA lymphocytes were similarly primed by DBA/2, three fractions were recovered (blasts, intermediate‐sized lymphocytes, and small lymphocytes), and the cells from each fraction were plated on syngeneic feeder layer. Only the progeny lymphocytes of the blast cells displayed the altered responses. Thus all, or almost all, activated cells may be selectively recovered in the blast fraction on the sixth day of one‐way mixed lymphocyte culture.