PRIMARY GENERATION OF CYTOLYTIC LYMPHOCYTES-T IN THE ABSENCE OF DNA-SYNTHESIS

The requirement for DNA synthesis during the primary differentiation of cytolytic T [thymus-derived] lymphocytes (CTL) were investigated. CTL were induced polyclonally in vitro by stimulation of normal C57BL/6 [mice] spleen cells with concanavalin (Con) A and their cytolytic activity was tested against 51Cr-labeled target cells in the presence of Bacto phytohemagglutinin M. With this system, CTL activity could first be detected 48 h after exposure of spleen cells to Con A. Addition of cytosine arabinoside at concentrations sufficient to reduce DNA synthesis by 95-98% in Con A-stimulated cultures did not significantly inhibit the generation of cytolytic activity on a cell-to-cell basis. Derepression of the genetic information required for the expression of CTL function can occur in the absence of detectable DNA synthesis.