Effect of melphalan in vitro on induction of murine suppressor T cells by ConA.

The effect of treatment with melphalan in vitro on the activity of spleen cells from BALB/c mice was investigated. Incubation of spleen cells with 1.5-5 micrograms melphalan/1 X 10(7) inhibited subsequent mitogenic stimulation by ConA or PHA and the allogeneic response of BALB/c spleen cells against C57B1 target spleen cells. Incubation of spleen cells with ConA led to induction of suppressor T cells which when added to fresh cultures inhibited the allogeneic response. Preincubation of spleen cells with melphalan even at low concentrations (0.15-0.5 micrograms 1 X 10(7) cells) which do not directly affect mitogenic stimulation or allogeneic response partially inhibited the generation of suppressor T cells by ConA. Treatment with melphalan had no effect on already induced suppressor T cells as shown by incubation of spleen cells with melphalan (0.15-5 micrograms/1 X 10(7) cells) after incubation with ConA. Addition of cells treated with melphalan alone (without ConA) to fresh cultures led to an increase in the allogeneic response.