Analyses of acute graft-versus-host-like reaction in [MRL/lpr----MRL/+] chimeric mice using MRL/lpr-Thy-1. 1 congenic mice.

When MRL/Mp(-)+/+(MRL/+) mice are lethally irradiated and then reconstituted with MRL/Mp-lpr/lpr (MRL/lpr) bone marrow and/or spleen cells, these MRL/+ mice develop "lpr-GVHD" which is similar to acute graft-versus-host disease (GVHD). Using a Thy-1 congenic strain of MRL/lpr mice (MRL/lpr-Thy-1.1), we analyzed T cell subpopulations in the thymus and spleen of MRL/+ mice suffering from lpr-GVHD. lpr-GVHD was induced in MRL/+ mice by transplantation of bone marrow cells (BMC) from MRL/lpr-Thy-1.1 mice; severe lymphocyte depletion associated with fibrosis was observed in the spleens after 7 weeks of bone marrow transplantation (BMT). Thymocytes of the host MRL/+ thymus were replaced with donor-derived cells from the early stage of lpr-GVHD, whereas in the spleen, a small number of host T cells (Thy-1.2+) (4-5%) were retained until the late stage of lpr-GVHD. Donor-type (Thy-1.1+) T cell subsets were not different from those of nontreated MRL/+ mice in the thymus, whereas in the spleen. CD8+ T cells (Thy-1.1+) reached a peak at 5 weeks after BMT, and CD4+ T cells (Thy-1.1+), a peak at 6 weeks. The elimination of T cells from MRL/lpr BMC had no evident effect on the prevention of lpr-GVHD. T cell subpopulations showed a similar pattern to GVHD elicited by MHC differences. Analyses of autoreactive T cells expressing V beta 5 or V beta 11 revealed that autoreactive T cells were deleted from the peripheral lymph nodes. Interestingly, the levels of IgG anti-ssDNA antibodies markedly increased, and both IgM and IgG rheumatoid factors slightly increased 5 to 7 weeks after BMT. These findings are discussed in relation to not only GVHD elicited by MHC differences but also autoimmune diseases.