Active suppression of in vitro reactivity of spleen cells after BCG treatment.

It was found that spleen cells from mice injected i.v. with large doses of BCG respond to PHA stimulation less intensely than do normal spleen cells. We were able to show that nylon wool column purified BCG treated T cells also had a low PHA reactivity. Unfractionated spleen cells, adherent cells or T-enriched populations from BCG treated mice, when added to normal T cells lowered their PHA reactivity. When the same BCG treated cell populations were added to tumor cells in vitro, they inhibited their growth.