Identification of alpha3, alpha4, and alpha5 chains of type IV collagen as alloantigens for Alport posttransplant anti-glomerular basement membrane antibodies.

BACKGROUND: Alport syndrome is a hereditary disorder of basement membranes especially affecting the kidneys, ears, and eyes. Some patients who undergo renal transplantation lose their kidneys as a result of posttransplant anti-glomerular basement membrane (anti-GBM) disease. METHODS: In the present study, we analyzed serum from 21 unselected Alport patients who underwent renal transplantation. Eleven samples were from patients without posttransplant anti-GBM nephritis, and 10 were from patients with this disease. RESULTS: Thirteen serum samples [10 alport posttransplant nephritis serum (APTN) and three Alport posttransplant serum (APT)] revealed linear binding to the GBM by indirect immunofluorescence. By using direct ELISA and immunoblotting with GBM constituents and type IV collagen NC1 domains from bovine, human, and recombinant sources, we detected anti-GBM antibodies in all Alport patients in varying titers. Five samples showed specific reactivity to the alpha3 chain, four to the alpha5 chain, six to both alpha3 and alpha5 chains, one to the alpha3 and alpha4 chains, and two to the alpha3, alpha4, and alpha5 chains of type IV collagen. The varied spectrum of reactivities was present equally in nephritic and non-nephritic sera. Ten control samples from non-Alport transplant patients did not exhibit specific binding to the GBM. CONCLUSIONS: These results suggest that the absence of alpha3, alpha4, and alpha5 chains of type IV collagen in the Alport kidney leads to alloantibodies in all Alport patients who receive transplants, irrespective of whether they develop nephritis or not. Although all Alport transplant patients develop this humoral response, only a select few develop anti-GBM disease. We suggest that this difference could be attributable to a genotypic effect on the ability of some individuals to launch a cell-mediated immune response.

Monocyte chemoattractant protein-1 mediates monocyte/macrophage influx in anti-thymocyte antibody-induced glomerulonephritis.

Chemokines are a family of chemotactic cytokines whose participation in inflammation in vivo remains to be established. To study the role of monocyte-chemoattractant-protein-1 (MCP-1) on the glomerular accumulation of leukocytes, rats received a neutralizing anti-MCP-1 antiserum following the induction of an glomerulonephritis by an anti-thymocyte antibody (ATS). The infiltration of monocytes/macrophages (M/M) and granulocytes was analyzed by immunohistology. When studied by Northern blotting, glomerular mRNA levels of MCP-1, and interleukin 1 beta (IL-1 beta) increased at three hours and 24 hours following the induction of the injury. The glomerular mRNA expression of intercellular adhesion molecule-1 (ICAM-1) only increased marginally, whereas the expression of the chemokine RANTES was not enhanced. In animals that received anti-MCP-1 antibody glomerular MCP-1 mRNA expression increased. However, the chemoattractant activity for monocytes released into supernatants of isolated glomeruli was reduced. The anti-MCP-1 antibody did not affect glomerular IL-1 beta, ICAM-1 or RANTES mRNA levels. The induction of glomerulonephritis was associated with an increased glomerular recruitment of polymorphonuclear granulocytes (PMNs) at three hours and M/M at 24 hours, when compared with controls. The anti-MCP-1 antiserum significantly reduced the glomerular M/M infiltration at 24 hours by 40%, but was without effect on glomerular PMN recruitment or growth of the resident glomerular cells. These studies demonstrate that MCP-1 is an important mediator for monocyte recruitment in this model of glomerulonephritis. The reduction of M/M infiltration might affect this glomerular injury.

The platelet activating factor receptor antagonist WEB 2170 improves glomerular hemodynamics and morphology in a proliferative model of mesangial cell injury.

Rats were treated with the platelet activating factor receptor antagonist WEB 2170 (15 mg/kg/day) in three different protocols to evaluate a possible role of platelet activating factor in an experimental proliferative model of glomerular disease. The glomerular immune injury was initiated by the i.v. administration of a rabbit anti-rat thymocyte antiserum. Anti-rat thymocyte antiserum induces a proliferative glomerulonephritis with reduction of glomerular filtration rate (614 +/- 94) compared with controls (1,120 +/- 192 microL/min/100 g body wt) when studied at day 7. Treatment of rats with WEB 2170 over 8 days (starting at day -1; protocol 1) ameliorated the loss in glomerular filtration rate (936 +/- 82 microL/min/100 g body wt) in nephritic rats at day 7; however, it had no effect on controls (1,142 +/- 104 microL/min/100 g body wt). Interventional treatment with WEB 2170 (starting at day 4 after anti-rat thymocyte antiserum; protocol 2) also improved glomerular function when glomerular filtration rate was already reduced (410 +/- 41 microL/min/100 g body wt) at day 4. The platelet activating factor receptor antagonist given at day 7 after induction of disease (protocol 3) did not improve impaired glomerular filtration rate. Preinterventional and interventional treatment with WEB 2170 reduced the infiltration of polymorphonuclear granulocytes in glomeruli. Interventional treatment with WEB 2170 also reduced glomerular morphologic damage in nephritic glomeruli. The data demonstrate a beneficial effect of the platelet activating factor receptor antagonist in this animal model of proliferative glomerulonephritis which suggests that platelet activating factor might play an important role in the mediation of this disease.

Immune-mediated mesangial cell injury--biosynthesis and function of prostanoids.

We studied the formation of cyclo-oxygenase products in a rat model of mesangial cell injury, in order to determine a possible role of prostaglandin E2 (PGE2), prostaglandin I2 (determined as 6-keto-PGF1 alpha and thromboxane A2 (TxA2) in immune-mediated glomerular disease. Selective immune-mediated mesangial cell injury was induced by i.v. administration of a rabbit anti-rat thymocyte antiserum (ATS). Intravenous ATS leads to immune deposits in the mesangium followed by mesangiolysis and the infiltration of polymorphonuclear granulocytes and monocytes. Glomerular TxB2 formation two hours (292 +/- 27 pg/mg/min) and 48 hours (396 +/- 69 pg/mg/min) following antibody was significantly (P less than 0.05) higher compared to animals receiving non-antibody rabbit IgG (TxB2: 2 hr 143 +/- 13; 48 hr 171 +/- 32 pg/mg/min). Treatment with cobra venom factor (CVF) and the reduction of glomerular monocyte infiltration inhibited the increase of glomerular TxB2 formation significantly. Depletion of granulocytes with a rabbit anti-rat granulocyte serum had no effect on glomerular prostanoid formation following ATS. Glomerular PGE2 and 6-keto PGF1 alpha production was not altered following ATS. Inulin clearance in rats with immune-mediated mesangial cell injury was significantly (P less than 0.001) lower at two hours (456 +/- 24 microliters/min/100 g body wt) and 48 hours (433 +/- 54 microliters/min/100 g body wt) compared to their corresponding control animals which were treated with non-antibody IgG (2 hr: 914 +/- 51; 48 hr: 694 +/- 79 microliters/min/100 g body wt).(ABSTRACT TRUNCATED AT 250 WORDS)