THY1-MARROW CELLS REGULATE THE INDUCTION OF MURINE SYNGENEIC GRAFT-VERSUS-HOST DISEASE( BONE)

A syngeneic graft-versus-host disease (GVE[D)-like syndrome has been s hown to be inducible in some strains of mice after lethal irradiation, reconstitution with syngeneic bone marrow (BM), and treatment with a short course of CsA therapy. Since Thy1+ BM cells have been shown to r egulate the development of other experimental autoimmune diseases, it was important to determine their role in the inducibility of syngeneic GVHD (SGVHD) in different strains of mice. Lethally irradiated mice w ere reconstituted with either syngeneic BM or T cell-depleted syngenei c BM, then treated with CsA or diluent. Removal of Thy1+ cells from BM before reconstitution of an inducible strain, C3H/HeN, exacerbated SG VHD when compared with animals given whole BM cells before CsA treatme nt. Furthermore, a noninducible strain, C57BL/6 mice, developed SGVHD when reconstituted with T cell-depleted syngeneic BM but not BM before CsA therapy. These results suggest that Thy1+ BM cells may regulate t he development of SGVED, and be of importance in controlling autoreact ivity after bone marrow transplantation.