Treatment of donor cells with L-leucyl-L-leucine methyl ester prevents induction of graft-vs-host-like reaction in [lpr/lpr----+/+] chimera.

Irradiated C57BL/6 (B6) mice which had received spleen cells from autoimmune-prone C57BL/6J-lpr/lpr (B6-lpr) mice underwent a graft-versus-host (GvH)-like reaction early after the spleen cell transfer, although both strains have the same background genes, including MHC and Mls gene, but differ only in a lpr gene. We analyzed the changes in this GvH-like reaction when the donor spleen cells had been treated with L-leucyl-L-leucine methyl ester, which has been reported to have an inhibitory effect on the early GvH reaction in allogeneic or semiallogeneic chimeras. The treatment of donor spleen cells completely abrogated the induction of the early phase of the GvH-like reaction in [B6-lpr----B6] chimeras. The results suggest that the GvH-like reaction in these chimeras is caused by a mechanism(s) similar to that operating in allogeneic or semiallogeneic chimeras.