Further studies on suppressor cell activity in the spleen of neonatal mice.

Spleen cells from newborn BDF₁ and C57BL/6 mice are tested for suppressor activity in mixed lymphocyte culture. The added spleen cells, treated with mitomycin, suppress both cell proliferation and the generation of cytotoxic cells. Thymus cells from newborn mice have little suppressor activity. Suppressor cells act across an allogeneic barrier, are cortisone-resistant, XR-resistant, T-cells and their activity is inversely correlated to the MLC reactivity in the spleen of the young animal. Incubation of neonatal suppressor cells on macrophage monolayers reduces suppressor cell activity and points to the possible importance of the macrophage in controlling immunological maturation.