Special differentiation requirements of original and enriched secondary cytotoxic T lymphocyte precursors (pCTL-2 memory cell) specific for the class I histocompatibility molecule.

The in vivo-induced pCTL-2 cells of the L3T4- Lyt-2+ phenotype specific for the H-2Kb molecule are converted into effector CTLs in mixed lymphocyte culture (MLC) in the presence of heat-treated donor stimulators much more efficiently when the donor and recipient differ from each other, not only in the major histocompatibility complex (MHC) class I (H-2Kb) (anti-B10.MBR B10.AKM) but also in the MHC classes I + II, i.e., Kb + Ib (anti-C57BL/6 B10.D2 (R101)). The differentiation of original pCTL-2 is enhanced as the result of a synergistic action of the Kb alloantigen and rIL-2 in small doses. The anti-Kb pCTL-2, after their separation from helper T cells non-adherent to the macrophage donor monolayer and their subsequent elution from it, give rise to pronounced differentiation in simplified conditions over 3 days in monoculture in the absence of both stimulators and rIL-2. It is suggested that spontaneous and highly efficient specific differentiation of the eluted pCTL-2 is due to a dramatically enhanced secretion of the CTL differentiation factor by pCTL-2 themselves, and in addition, rIL-2 can also contribute to the secretion of this factor.