Selective killing of mitogen-induced transformed cells by quinine sulfate in vitro

Increase in incorporation of 3H-thymidine ([3H-]-Tdr) in blast-transformed cells was induced in vitro by either lipopolysaccharide or concanavalin A (Con A) in spleen cells of Balb/c mice and by Con A in rabbit peripheral lymphocytes. Small lymphocytes were not affected by the addition of quinine to the medium. This was shown by a dye exclusion test and by mitogen stimulation after exposure and removal of quinine from the medium. On the other hand, immunoblasts were not formed in lymphocyte cultures containing both quinine and the cell mitogen. The degree of [3H]-Tdr incorporation after mitogenic stimulation was also markedly reduced by subsequent addition of quinine. An incubation period of at least 5 h was required for the expression of quinine effect. It is concluded that quinine acts as a cytotoxic agent for immunoblasts in vitro.