DIFFERENT MEDIATOR SYSTEMS IN BIPHASIC HETEROLOGOUS PHASE OF ANTI-GBMNEPHRITIS IN MICE

Background. After the injection of rabbit anti-mouse glomerular baseme nt membrane (GBM) antibody into normal C57BL/6J mice severe albuminuri a develops, which reaches a peak at 24 h. This early albuminuria is de pendent on polymorphonuclear granulocytes (PMN) and is completely abse nt in the congenic beige mutant strain (C57BL/6J, bg/bg), which is gen etically deficient in leukocytic neutral proteinase activity. We now s tudied the development of anti-GBM nephritis in beige mice during the later heterologous phase. Methods. In untreated beige mice we assessed the albuminuria and glomerular lesions on days 1-5 after i.v. injecti on of anti-GBM antibody. Secondly, effector mechanisms involved in the later days of the heterologous phase were studied by substitution of whole anti- GBM antibodies by F(ab')(2) fragments, by leukocyte deplet ion (total body irradiation), scavenging of reactive oxygen metabolite s (dimethylsulfoxide treatment), and complement depletion (cobra venom factor treatment). Results. In the later part of the heterologous pha se (days 2-5), when there is still no sign of autologous antibody form ation, i.v. injection of anti-GBM antibodies in beige mice induces nep hritis with gradually increasing albuminuria, that reaches levels simi lar to those in non-deficient, congenic controls by day 3. This late a lbuminuria did not occur after injection of F(ab')(2) fragments of the antibody, could be prevented by leukocyte depletion, and was greatly reduced by treatment with dimethylsulfoxide, a scavenger of hydroxyl r adicals. The late albuminuria was not influenced by complement depleti on with cobra venom factor. Histologic and immunohistologic studies ga ve no indication for a role of glomerular macrophages or lymphocytes. Conclusions. The heterologous phase in murine anti-GBM nephritis is a biphasic process, with sequential involvement of different and indepen dent mediating systems: both phases are PMN-dependent, but only the ea rly albuminuria depends on leukocytic neutral proteinase activity, whe reas the albuminuria and the glomerular damage at later days are effec ted by reactive oxygen metabolites, most probably originating from PMN accumulating in the glomerulus.