Provocation of skin graft rejection across murine class II differences by non--bone-marrow-derived cells

We have evaluated the relative contribution of bone-marrow-derived cells to skin allograft immunogenicity in mice differing only at class II major histocompatibility genes by using bone marrow radiation chimeras as donors. The mouse strains used were C57BL/6Kh (B6) and B6.C-H-2bm12 (bm12), which differ only at at A beta gene of the I region of the mouse H-2 complex. Our results demonstrated that skin from (B6----bm12) chimeras was accepted by bm12 recipients and rejected by B6 mice in a manner indistinguishable from that of normal bm12 skin. Likewise, naive bm12 mice rejected (bm12----B6) chimeric skin and normal B6 skin equally well, and B6 animals accepted both types of skin grafts. Our data argues that the donor cell-type leading to graft rejection across limited I region differences is not of bone marrow origin, and that these cells must--at least under certain circumstances--express class II antigens.