Defective maintenance of T cell tolerance to a superantigen in MRL-lpr/lpr mice

Analyses of lpr-GVHD by adoptive transfer experiments 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) spleen and/or bone marrow cells (BMCs), the mice develop a graft-versus-host disease (GVHD)-like syndrome which is known as lpr-GVHD. We analyzed lpr-GVHD by adoptive transfer experiments using congenic MRL/lpr-Thy-1.1 mice to distinguish the donor and recipient cells. MRL/+ mice were lethally (9.5 Gy) irradiated and then reconstituted with BMCs of MRL/lpr-Thy-1.1 mice treated with anti-Thy-1.1 monoclonal antibody (mAb) plus complement (C). The mice were sacrificed 5 to 6 weeks after bone marrow transplantation (BMT), and the spleen cells were transferred to second recipients. The second recipients (MRL/+ or MRL/lpr mice) were non-irradiated, sublethally (6 Gy) irradiated or lethally (9.5 Gy) irradiated. The lethally irradiated mice were also injected with syngeneic BMCs treated with anti-Thy-1.2 mAb plus C. When whole spleen cells (1 x 10(8) were injected into lethally irradiated MRL/+ mice, the mice showed short survival (1.2-1.5 months) and severe histological changes in the spleen (atrophy and fibrosis), liver (lymphoid infiltration in the Glisson's sheath) and lung (lymphoid infiltration around the bronchus and vessel). The sublethally irradiated MRL/+ mice at 2 months after transfer showed histological changes similar to the lethally irradiated MRL/+ recipients, although the former survived more than 3 months, suggesting that histological changes do not reflect on mortality. These GVH-like diseases were not transferable to MRL/lpr mice; they developed autoimmune diseases.(ABSTRACT TRUNCATED AT 250 WORDS)

Non-MHC-linked genes in autoimmune diseases

Single-locus mutations in mice associated with autoimmune manifestations or influencing them, including lpr, motheaten and xid have been characterized at the molecular level. Mutations have been described in the genes encoding Fc gamma RI, interleukin-2 and natural resistance associated macrophage protein, which are all candidate genes for susceptibility loci associated with autoimmune diabetes in non-obese diabetic mice. Twelve regions of DNA that are associated with disease susceptibility have now been identified in this polygenic model of autoimmunity. In human autoimmune diseases, the region of DNA surrounding the insulin gene that is associated with susceptibility to insulin dependent diabetes mellitus has been narrowed down to 4.1 kilobases.

Mature T cells of autoimmune lpr/lpr mice have a defect in antigen-stimulated suicide

Antigen receptor-stimulated cell death of developing, immature T cells plays an important role in shaping the repertoire of antigens to which mature T cells will respond, but a role for receptor-stimulated death in controlling responses of mature T cells is controversial. Mutant lpr/lpr mice exhibit an autoimmune syndrome similar to systemic lupus erythematosus. Here we demonstrate that these mice have a defect in antigen-stimulated suicide of activated T cells in mature CD4+ and CD8+ T cell compartments. The defective suicide pathway is evident when the T cells are stimulated with antigen on antigen-presenting cells or with immobilized anti-CD3 in the absence of antigen-presenting cells. These studies, in concert with the work of others, suggest that antigen-stimulated death of mature cells may be important both in establishing peripheral tolerance and in limiting inflammation during normal immune responses.