Glomerular T cells in Heymann nephritis

Heymann nephritis in Lewis rats

Human membranous nephritis is a major cause of end-stage kidney disease. Active Heymann nephritis (HN) is an auto-immune model of membranous nephritis induced in Lewis rats by immunization with a crude renal tubular antigen (Fx1A) or megalin (gp330). The pathogenesis of HN is through the binding of anti-Fx1A autoantibodies to the auto-antigen expressed on glomerular epithelial cells, resulting in severe glomerular injury and proteinuria. The pathological features of HN include immune deposits in glomeruli and infiltration of glomeruli and the tubulointerstitium by macrophages and T cells. This unit describes the method of the preparation of Fx1A and the induction of HN in Lewis rats by immunization with Fx1A.

CD8+ regulatory T cells induced by T cell vaccination protect against autoimmune nephritis

Autoreactive T cells play a pivotal role in the pathogenesis of autoimmune kidney disease. T cell vaccination (TCV) may limit autoimmune disease and induce CD8+ regulatory T cells (Tregs). We used Heymann nephritis (HN), a rat model of human membranous nephritis, to study the effects of TCV on autoimmune kidney disease. We harvested CD4+ T cells from renal tubular antigen (Fx1A) -immunized rats and activated these cells in vitro to express the MHC Class Ib molecule Qa-1. Vaccination of Lewis rats with these autoreactive Fx1A-induced T cells protected against HN, whereas control-primed T cells did not. Rats that underwent TCV had lower levels of proteinuria and serum creatinine and significantly less glomerulosclerosis, tubular damage, and interstitial infiltrates. Furthermore, these rats expressed less IFN-γ and IL-6 in splenocytes, whereas the numbers of Tregs and the expression of Foxp3 were unchanged. In vitro cytotoxicity assays showed CD8+ T cell-mediated elimination of Qa-1-expressing CD4+ T cells. In vivo, TCV abrogated the increase in Qa-1-expressing CXCR5+ TFH cells observed in HN compared with controls. Taken together, these results suggest that TCV protects against autoimmune kidney disease by targeting Qa-1-expressing autoreactive CD4+ cells.

Intramolecular epitope spreading in Heymann nephritis

Immunization with megalin induces active Heymann nephritis, which reproduces features of human idiopathic membranous glomerulonephritis. Megalin is a complex immunological target with four discrete ligand-binding domains (LBDs) that may contain epitopes to which pathogenic autoantibodies are directed. Recently, a 236-residue N-terminal fragment, termed "L6," that spans the first LBD was shown to induce autoantibodies and severe disease. We used this model to examine epitope-specific contributions to pathogenesis. Sera obtained from rats 4 weeks after immunization with L6 demonstrated reactivity only with the L6 fragment on Western blot, whereas sera obtained after 8 weeks demonstrated reactivity with all four recombinant fragments of interest (L6 and LBDs II, III, and IV). We demonstrated that the L6 immunogen does not contain the epitopes responsible for the reactivity to the LBD fragments. Therefore, the appearance of antibodies directed at LBD fragments several weeks after the primary immune response suggests intramolecular epitope spreading. In vivo, we observed a temporal association between increased proteinuria and the appearance of antibodies to LBD fragments. These data implicate B cell epitope spreading in antibody-mediated pathogenesis of active Heymann nephritis, a model that should prove valuable for further study of autoimmune dysregulation.

DNA vaccination with naked DNA encoding MCP-1 and RANTES protects against renal injury in adriamycin nephropathy

BACKGROUND

We have previously shown that monocyte chemoattractant protein-1 (MCP-1) and regulated upon activation, normal T-cell expressed and secreted (RANTES) are significantly increased in renal cortex in adriamycin nephropathy. In this study, we tested the effect of DNA vaccination encoding the C-C chemokines MCP-1 and RANTES in a rat model of adriamycin nephropathy.

METHODS

Both reverse transcription-polymerase chain reaction (RT-PCR) products of MCP-1 and RANTES used as constructs were cloned into a pTarget vector for naked DNA vaccination. Two hundred micrograms of DNA was injected into the tibialis anterior muscle four times at weekly intervals. One week after the last DNA vaccination, rats received adriamycin. All animals were sacrificed 4 weeks after adriamycin administration. Changes in renal function and histologic features were assessed. Enzyme-linked immunosorbent assay (ELISA) and Western blot were used for autoantibody determination. Antibody specificity was assessed in in vitro transmigration assays.

RESULTS

Chemokine DNA vaccination significantly reduced proteinuria (P < 0.05) and ameliorated creatinine clearance (P < 0.05) at 2, 3, and 4 weeks after adriamycin administration. Morphometric analysis showed less glomerular sclerosis (P < 0.001) and interstitial infiltrates (P < 0.005) in chemokine DNA vaccination group compared with control groups. Anti-MCP-1 and RANTES autoantibodies were detected in higher concentrations in chemokine DNA vaccinated rats than in control rats (P < 0.001) and serum from vaccinated rats blocked T-cell transmigration to MCP-1 and RANTES.

CONCLUSION

In this study, we have shown that naked DNA vaccination against MCP-1 and RANTES ameliorates the progression of renal disease in the rat adriamycin nephropathy model of chronic proteinuric renal disease. The protective mechanism may involve the production of autoantibodies against MCP-1 and RANTES.

“Pruning” of Alloreactive CD4+T Cells Using 5- (and 6-)Carboxyfluorescein Diacetate Succinimidyl Ester Prolongs Skin Allograft Survival

Removal of alloreactive cells by either thymic deletion or deletion/anergy in the periphery is regarded as crucial to the development of tolerance. Dyes, such as CFSE, that allow monitoring of cell division suggest that in vitro proliferation could be a used as a way of "pruning" alloreactive cells while retaining a normal immune repertoire with retention of memory to previously encountered pathogens. This would overcome the problems occurring as a result of therapies that use massive depletion of T cells to allow acceptance of organ transplants or bone marrow grafts. We therefore used a skin graft model of CD4-mediated T cell rejection across a major H-2 mismatch (C57BL/6 (H-2(b)) to BALB/c (H-2(d)) mice) to evaluate whether nondividing CD4(+) T cells derived from a mixed lymphocyte culture would exhibit tolerance to a skin graft from the initial stimulator strain. We demonstrate that selective removal of dividing alloreactive CD4(+) T cells resulted in marked specific prolongation of allogeneic skin graft survival, and that the nondividing CD4(+) T cells retained a broad TCR repertoire and the ability to maintain memory. This novel way of depleting alloreactive T cells may serve as a useful strategy in combination with other mechanisms to achieve transplant tolerance.

Glomerular T Cells Are of Restricted Clonality and Express Multiple CDR3 Motifs across Different Vβ T-Cell Receptor Families in Experimental Autoimmune Glomerulonephritis

Experimental autoimmune glomerulonephritis (EAG) is an animal model of Goodpasture's disease which can be induced in Wistar-Kyoto (WKY) rats by a single intramuscular injection of collagenase-digested rat glomerular basement membrane (GBM) in adjuvant. This model is characterised by anti-GBM antibody production, accompanied by focal necrotising glomerulonephritis with crescent formation and glomerular infiltration by T cells and macrophages. Previous work has shown that EAG is a T-cell-dependent disease. We proposed that intraglomerular T cells might be directly involved in pathogenesis and would be oligoclonal. In this study, EAG was induced by standard methods, the kidneys perfused with saline at week 2 and week 4, and the glomeruli separated by a sieving method. Glomerular RNA was extracted and reverse transcribed. RT-PCR showed overexpression of an average of two Vbeta families in each kidney analysed. However, no predominant single Vbeta family was overexpressed in any of the experimental animals. CDR3 spectratyping of Fam-labelled PCR products showed a marked restriction involving different Vbeta families. Sequencing demonstrated multiple CDR3 motifs, each expressed in association with different Vbeta gene segments. Our results show that glomerular T cells are of restricted clonality and suggest a role for antigen-specific effector T cells in the pathogenesis of EAG.

Matching T-cell receptors identified in renal biopsies and urine at the time of acute rejection in pediatric renal transplant patients

Urinary monitoring of kidney allograft function has been used for many years. More recently, molecular identification of cytotoxic T-cell products has been used as a diagnostic tool in acute rejection. Monitoring of T-cell infiltrates by analysis of the T-cell receptor (TcR) gene usage has been performed on biopsies with acute and chronic rejection, but not on urine samples. The aim of this study was to identify and compare TRBV gene usage assessing the CDR3 (Complementarity Determining Region 3) length distribution and sequence in urine and biopsies of pediatric renal allograft patients at the time of acute rejection and compare them with peripheral blood. We studied four pediatric renal transplant recipients with acute cellular rejection. We identified restricted and matched TRBV CDR3 spectratypes with overexpressed TRBV families and show identical, clonally expanded TRBV CDR3 sequences in all four patients present in the urine and renal allograft. We demonstrate that urinary monitoring can detect graft-infiltrating lymphocytes in acute rejection and may have a role in the monitoring of renal transplants.

T cell receptor BV repertoires using real time PCR: a comparison of SYBR green and a dual-labelled HuTrec fluorescent probe

Real time PCR is a useful tool in immunological research but little has been published on the use of this technique in the measurement of T cell receptor (TCR) BV repertoires. We have compared the performance of SYBR green with that of a dual-labeled HuTrec (Human T cell receptor) fluorescent probe system. Serial dilutions of peripherals blood mononuclear cells were tested to compare the consistency of the two systems across multiple T cell receptor signal levels. Samples were diluted with non-TCR cDNA to simulate a low-level TCR signal within a tissue sample. The fluorogenic probe gave highly consistent results with a correlation coefficient of greater than 0.9 across a samples. SYBR green showed accurate results only when tested with high signal samples. Low-signal cDNA gave very poor results with SYBR green compared to the HuTrec fluorogenic probe with correlation coefficients as low as 0.65. Poorest performance occurred in the context of the simulated tissue sample with a high level of non-TCR DNA. Under these conditions, large amounts of nonspecific PCR product were generated which were detected by the SYBR green system and therefore distorted the results. SYBR green performed poorly when used with samples contaminated with significant quantities of non-target cDNA and samples with low target signal. It is therefore not an appropriate method for the measurement of TCR repertoires in small tissue samples. A dual-labeled HuTrec fluorescent probe produced a consistent TCR repertoire across a broad range of TCR signal levels and proved robust in the presence of contaminating non-TCR cDNA. We recommend the use of such a fluorescent probe in real time PCR for the assessment of TCR repertoires in small tissue samples. Where samples are assayed using SYBR green, agarose gel confirmation of PCR product specificity should be provided.

Conformation and glycosylation of a megalin fragment correlate with nephritogenicity in Heymann nephritis

Active Heymann nephritis (AHN), a rat model of autoimmune glomerulonephritis, is induced by immunization with autologous megalin, a 600-kDa cell surface glycoprotein isolated from crude renal extracts. Recombinant proteins containing a 563-residue N-terminal sequence of megalin were obtained from Escherichia coli and baculovirus-insect cell expression systems. Rats immunized with the soluble, secreted protein encoded by a baculovirus construct elicited high titer anti-megalin autoantibodies and developed glomerular immune deposits and elevated proteinuria consistent with AHN. Rats treated with the bacterial or nonsecreted insect cell proteins produced a milder anti-megalin response and did not develop the disease. Nephritogenicity appeared to correlate with conformational or other structural features of native megalin. All three recombinant proteins were reactive in Western blots with rabbit anti-megalin antiserum, whereas the insect cell-derived proteins reacted preferentially in Western blot and ELISA with anti-megalin autoantibodies from rats with AHN induced by native megalin. Only the secreted insect cell product was stained in a lectin blot, suggesting its specific glycosylation. These observations provide evidence that a megalin N-terminal domain includes B and T cell epitopes sufficient for a pathogenic autoimmune response and that a native-like conformation and glycosylation are essential for the induction of disease. The importance of conformational B cell epitopes for pathogenic autoantibodies recapitulates observations made in other models of organ-specific autoimmune disease. Glycosidic modifications could influence the presentation of either B or T cell epitopes in AHN, consistent with emerging evidence of the role of post-translational modifications in pathogenic autoimmune responses.

DNA Vaccination Against Specific Pathogenic TCRs Reduces Proteinuria in Active Heymann Nephritis by Inducing Specific Autoantibodies

We have previously identified potential pathogenic T cells within glomeruli that use TCR encoding Vbeta5, Vbeta7, and Vbeta13 in combination with Jbeta2.6 in Heymann nephritis (HN), a rat autoimmune disease model of human membranous nephritis. Vaccination of Lewis rats with naked DNA encoding these pathogenic TCRs significantly protected against HN. Proteinuria was reduced at 6, 8, 10, and 12 wk after immunization with Fx1A (p < 0.001). Glomerular infiltrates of macrophages and CD8(+) T cells (p < 0.005) and glomerular IFN-gamma mRNA expression (p < 0.01) were also significantly decreased. DNA vaccination (DV) causes a loss of clonality of T cells in the HN glomeruli. T lymphocytes with surface binding of Abs were found in DNA vaccinated rats. These CD3(+)/IgG(+) T cells expressed Vbeta5 and Vbeta13 that the DV encoded. Furthermore, FACS shows that these CD3(+)/IgG(+) cells were CD8(+) T cells. Analysis of cytokine mRNA expression showed that IL-10 and IFN-gamma mRNA were not detected in these CD3(+)/IgG(+) T cells. These results suggest that TCR DNA vaccination produces specific autoantibodies bound to the TCRs encoded by the vaccine, resulting in blocking activation of the specific T cells. In this study, we have shown that treatment with TCR-based DV, targeting previously identified pathogenic Vbeta families, protects against HN, and that the mechanism may involve the production of specific anti-TCR Abs.