Cloned natural suppressor cells prevent lethal graft-vs-host disease

Cloned natural suppressor (NS) cell lines derived from the spleens of TLI-treated adult BALB/c or neonatal BALB/c mice were assayed for their ability to inhibit acute GVHD in vivo. Two assay systems were used to measure GVHD: spleen enlargement of F1 hybrid neonates, and mortality of sublethally irradiated homozygous weanling mice after the i.p. injection of fresh allogeneic spleen cells. Both lines of NS cells significantly reduced GVHD, but the control HT-2 cell line (T cell line of BALB/c origin) did not affect GVHD. The NS cells reduced GVHD regardless of the strain combination of the donor and recipient. Thus, suppression occurred without restriction by the major histocompatibility complex, and without antigenic specificity.