Production and characterization of new monoclonal antibodies that distinguish subsets of mink lymphoid cells

Roles of endogenous retroviruses and platelets in the development of vascular injury in spontaneous mouse models of autoimmune diseases

MRL/MpJ-lpr/lpr (MRL/lpr) mice spontaneously develop immune complex-mediated glomerulonephritis, granulomatous arteritis, and thrombocytopenia. Recent genetic analyses in a few different strains of lupus-prone mice have pointed out a close correlation between autoantibodies reactive with the endogenous retroviral env gene product, gp70, and the development and severity of glomerulonephritis. We have also shown that autoantibodies reactive with endogenous retroviral gp70 are closely correlated with the development of necrotizing polyarteritis in another lupus-prone strain of mice, SL/Ni. However, suggested pathogenicity of anti-gp70 autoantibodies has not yet been directly tested. To examine if anti-gp70 autoantibodies induce glomerular and vascular pathology, we established from unmanipulated MRL/lpr mice hybridoma clones that secrete monoclonal antibodies reactive with endogenous xenotropic viral env gene products. As reported separately, a high proportion of these anti-gp70 antibody-producing hybridoma clones induced in syngeneic non-autoimmune and severe combined immunodeficiency mice proliferative or wire loop-like glomerular lesions with granular deposits of gp70, IgG, and C3 in affected glomeruli. Some mice transplanted with these anti-gp70 autoantibody-producing hybridoma cells also showed massive subendothelial deposition of electron-dense materials in small arterioles in the kidneys. Furthermore, we identified an IgG2a-producing anti-gp70 hybridoma clone that induced microvascular intraluminal platelet aggregation, thrombocytopenia, and amenia upon transplantation into syngeneic non-autoimmune mice. This anti-gp70 autoantibody bound onto the surfaces of mouse platelets, and specifically precipitated a platelet protein with an approximate relative molecular mass of 40000. Attachment of activated platelets to the intimal surfaces of small arteries was also observed by electron microscopy in mice transplanted with the pathogenic anti-gp70 IgG2a-producing hybridoma cells, suggesting an interaction between antibody-bound platelets and endothelial cells.

Establishment of monoclonal anti-retroviral gp70 autoantibodies from MRL/lpr lupus mice and induction of glomerular gp70 deposition and pathology by transfer into non-autoimmune mice

Several strains of mice, including MRL/MpJ mice homozygous for the Fas mutant lpr gene (MRL/lpr mice), F(1) hybrids of New Zealand Black and New Zealand White mice, and BXSB/MpJ mice carrying a Y-linked autoimmune acceleration gene, spontaneously develop immune complex-mediated glomerulonephritis. The involvement of the envelope glycoprotein gp70 of an endogenous xenotropic virus in the formation of circulating immune complexes and their deposition in the glomerular lesions have been demonstrated, as has the pathogenicity of various antinuclear, antiphospholipid, and rheumatoid factor autoantibodies. In recent genetic linkage studies as well as in a study of cytokine-induced protection against nephritis development, the strongest association of serum levels of gp70-anti-gp70 immune complexes, rather than the levels of antinuclear autoantibodies, with the development and severity of glomerulonephritis has been demonstrated, suggesting a major pathogenic role of anti-gp70 autoantibodies in the lupus-prone mice. However, the pathogenicity of anti-gp70 autoantibodies has not yet been directly tested. To examine if anti-gp70 autoantibodies induce glomerular pathology, we established from unmanipulated MRL/lpr mice hybridoma clones that secrete monoclonal antibodies reactive with endogenous xenotropic viral env gene products. Upon transplantation, a high proportion of these anti-gp70 antibody-producing hybridoma clones induced in syngeneic non-autoimmune and severe combined immunodeficiency mice proliferative or wire loop-like glomerular lesions. Furthermore, deposition of gp70 in glomeruli and pathological changes were observed after intravenous injection of representative clones of purified anti-gp70 immunoglobulin G, demonstrating pathogenicity of at least some anti-gp70 autoantibodies.

Induction of microthrombotic thrombocytopenia in normal mice by transferring a platelet-reactive, monoclonal anti-gp70 autoantibody established from MRL/lpr mice: an autoimmune model of thrombotic thrombocytopenic purpura

MRL/MpJ-lpr/lpr (MRL/lpr) mice spontaneously develop immune complex-mediated glomerulonephritis and thrombocytopenia. Although the presence of cross-reactive anti-phospholipid antibodies in sera of MRL/lpr mice has been demonstrated, possible relationships between detected autoantibodies and the development of thrombocytopenia have not been elucidated. Recent genetic analyses in a few different strains of lupus-prone mice have pointed out a close correlation between autoantibodies reactive with endogenous retroviral env gene product, gp70, and the development and severity of glomerulonephritis. In the process of establishing possibly nephritogenic anti-gp70 autoantibody-producing hybridoma cells from MRL/lpr mice, we identified an IgG2a-producing anti-gp70 hybridoma clone that induced microvascular intraluminal platelet aggregation, thrombocytopenia, and amenia upon transplantation into syngeneic non-autoimmune mice. This and two other anti-gp70 antibodies bound onto the surface of mouse platelets, and purified IgG2a of the anti-gp70 autoantibody induced glomerular lesions with characteristics of thrombotic thrombocytopenic purpura when injected into non-autoimmune mice. The pathogenic anti-gp70 autoantibody specifically precipitated a platelet protein with an approximate relative molecular mass of 40 000.

Production and characterization of monoclonal antibodies against mink leukocytes

Three monoclonal antibodies (mAbs) were generated against mink leukocytes. One antibody reacted with all T lymphocytes, one with all monocytes and one had platelet reactivity. Under reducing conditions, the T lymphocyte reactive antibody immunoprecipitated 18 kDa, 23 kDa, 25 kDa and 32-40 kDa polypeptides and the platelet reactive antibody 17 kDa, 22 kDa plus two high molecular weight (> 100 kDa) polypeptides. Immunohistological studies of the mAbs were performed in order to localize the cellular distribution of the detected antigens in various organs. The T lymphocyte reactive antibody detected an antigen, which was widely distributed in the T cell area of lymph nodes and spleen and in the thymic medulla. We conclude that this antibody is an anti-CD3 mAb and suggest that the platelet reactive antibody reacts to the CD41/CD61 integrin molecule. In addition to our own mAbs, more than 100 mAbs against leukocytes of human and various animal species have been analysed for cross-reactivity to mink leukocytes. We found eight to cross-react with mink. Of particular importance was an anticanine CD11a mAb, an antihuman CD79a mAb and an antihuman bcl-2 mAb.