Spontaneous recovery from early glomerular inflammation is associated with resistance to anti-GBM glomerulonephritis: tolerance and autoimmune tissue injury

ID3 may protect mice from anti‑GBM glomerulonephritis by regulating the differentiation of Th17 and Treg cells

Anti‑glomerular basement membrane glomerulonephritis (anti‑GBM GN) is an autoimmune disease that leads to severe and rapidly progressive renal injury. Inhibition of DNA‑binding factor 3 (ID3) serves a key role in autoimmune diseases, such as asthma and Sjögren's syndrome, and in experimental allergic encephalitis models. However, the role of ID3 in the progression of anti‑GBM GN remains unknown. In the present study, ID3 mRNA expression increased between 3‑ and 20‑fold in the renal tissues of anti‑GBM GN mice compared with the Control group, with a peak at day 14 post‑induction. In addition, ID3 protein expression was upregulated from day 7 onwards. The expression of ID3 was also examined in the spleen, and was demonstrated to be increased in the spleen of nephritic mice. T helper 17 (Th17) cells and regulatory T (Treg) cells were present throughout the entire period of observation (from day 7 to day 28) in anti‑GBM GN mice, which may vary at different time points, accompanied with the expression of ID3. In vitro, ID3 expression was increased when CD4+ T cells differentiated into Tregs; however, expression was lower in Th17 cells. Following treatment with ID3 small interfering RNA, RAR‑related orphan receptor γt, but not forkhead box P3, expression increased. Furthermore, increased expression of interleukin‑17A was also observed when ID3 was blocked. In addition, ID3 was able to interact with transcription factor E2A. A significant increase in binding between ID3 and E2A was observed in anti‑GBM GN from day 7 onwards, with a peak at day 14 in both renal tissue and spleen. In conclusion, ID3 may be involved in the differentiation of Th17 and Tregs by downregulating Th17 cells, which is probably associated with binding to E2A. The present results suggested that ID3 may offer protection against anti‑GBM GN in mice.

CD8αα+MHC Class II+ Cell with the Capacity To Terminate Autoimmune Inflammation Is a Novel Antigen-Presenting NK-like Cell in Rats

Discovery of immune tolerance mechanisms, which inhibit pre-existing autoimmune inflammation, may provide us with new strategies for treating autoimmune diseases. We have identified a CD8αα⁺MHC class II⁺ cell with professional APC capacity during our investigation on spontaneous recovery from autoimmune glomerulonephritis in a rat model. This cell actively invades inflamed target tissue and further terminates an ongoing autoimmune inflammation by selective killing of effector autoreactive T cells. In this study, we show that this cell used a cytotoxic machinery of Ly49s⁺ NK cells in killing of target T cells. Thus, this CD8αα⁺MHC class II⁺ cell was a dually functional Ag-presenting NK-like (AP-NK) cell. Following its coupling with target T cells through Ag presentation, killing stimulatory receptor Ly49s6 and coreceptor CD8αα on this cell used rat nonclassic MHC class I C/E16 on the target T cells as a ligand to initiate killing. Thus, activated effector T cells with elevated expression of rat nonclassic MHC class I C/E16 were highly susceptible to the killing by the CD8αα⁺ AP-NK cell. Granule cytolytic perforin/granzyme C from this cell subsequently mediated cytotoxicity. Thus, inhibition of granzyme C effectively attenuated the killing. As it can recognize and eliminate effector autoreactive T cells in the inflamed target tissue, the CD8αα⁺ AP-NK cell not only represents a new type of immune cell involved in immune tolerance, but it also is a potential candidate for developing a cell-based therapy for pre-existing autoimmune diseases.

Differentiating Glomerular Inflammation from Fibrosis in a Bone Marrow Chimera for Rat Anti-Glomerular Basement Membrane Glomerulonephritis

BACKGROUND

Many types of glomerulonephritis (GN) undergo tandem connected phases: inflammation and fibrosis. Fibrosis in human GNs leads to irreversible end-stage disease. This study investigated how these 2 phases were controlled.

METHODS

Using a rat anti-glomerular basement membrane GN model, we established bone marrow (BM) chimeras between GN-resistant Lewis (LEW) and GN-susceptible Wistar Kyoto (WKY) rats. Glomerular inflammation and fibrosis were compared between chimeras.

RESULTS

LEW's BM to WKY chimeras with or without co-transfer of host WKY's T cells were GN-resistant. On the other hand, WKY's BM to LEW (LEW(WKY)) chimeras developed glomerular inflammation and albuminuria upon immunization. Quantitative analysis showed that the number and composition of inflammatory cells in glomeruli of immunized LEW(WKY) chimeras were similar to those in immunized WKY rats at their inflammatory peak. Thus, glomerular inflammation was controlled by BM-derived non-T cell populations. However, unlike WKY rats, LEW(WKY) rats did not develop fibrosis until the end of experiments (84 days) in spite of persistent inflammation and albuminuria.

CONCLUSION

Inflammation alone was not sufficient to trigger fibrosis, suggesting a critical role of glomerular cells in the fibrotic process. As LEW(WKY) chimera allows us to separate glomerular inflammation from fibrosis, this model provides a useful tool to study how fibrosis is initiated following inflammation.

Peripheral blood CD8αα+CD11c+MHC-II+CD3- cells attenuate autoimmune glomerulonephritis in rats

In an anti-GBM glomerulonephritis (GN) model, GN-resistant Lewis rats naturally recover from early glomerular inflammation. Here we investigated recovery mechanisms for development of a potential immunotherapy for autoimmune GN. Our previous studies suggested that glomeruli-infiltrating leukocytes with a phenotype of CD8αα⁺CD11c⁺MHC⁻II⁺CD3⁻ (GIL CD8αα⁺ cells) were responsible for recovery through induction of T cell apoptosis. Now, we identified peripheral blood CD8αα⁺CD11c⁺MHC⁻II⁺CD3⁻ cells (PBMC CD8αα⁺CD3⁻ cells), which shared 9 markers with GIL CD8αα⁺ cells. Upon incubation, PBMC CD8αα⁺CD3⁻ cells displayed a morphology resembling that of dendritic cells. Similar to GIL CD8αα⁺ cells, PBMC CD8αα⁺CD3⁻ cells were capable of inducing T cell apoptosis in vitro. Hence, PBMC CD8αα⁺CD3⁻ cells were likely the precursor of GIL CD8αα⁺ cells. We next tested their potential in vivo function. PBMC CD8αα⁺CD3⁻ cells were able to infiltrate inflamed but not normal glomeruli. Isolated PBMC CD8αα⁺CD3⁻ cells of Lewis rats were transferred into GN-prone Wistar Kyoto rats at early inflammatory stage (day 17–25). When examined at day 45, both histopathology and BUN/serum creatinine level showed significantly attenuated GN in 80% of cell recipient Wistar Kyoto rats. Separate experiments verified infiltration of transferred Lewis PBMC CD8αα⁺CD3⁻ into the glomeruli, accompanied with apoptotic CD4⁺ T cells in the glomeruli of the recipient Wistar Kyoto rats. Thus, PBMC CD8αα⁺CD3⁻ cells of Lewis rats were able to terminate ongoing autoimmune inflammation in the glomeruli.

Natural recovery from antiglomerular basement membrane glomerulonephritis is associated with glomeruli-infiltrating CD8α+CD11c+MHC class II+ cells

BACKGROUND/AIMS

In an antiglomerular basement membrane glomerulonephritis (GN) model, GN-resistant Lewis (LEW) rats naturally recover from early glomerular inflammation (days 21-23). We have previously identified a glomeruli-infiltrating CD8α(+)CD11(high)MHC II(+) cell (GIL CD8α(+) cell) in GN-prone Wistar Kyoto (WKY) rats, which terminates glomerular inflammation through inducing T cell apoptosis prior to glomerular fibrosis at days 35-40. We investigated if GIL CD8α(+) cells were also associated with the recovery in LEW rats.

METHODS

GIL CD8α(+) cells in LEW rats were characterized; their infiltration was observed in connection with T cell apoptosis in glomeruli.

RESULTS

An influx of GIL CD8α(+) cells into inflamed glomeruli was confirmed in the immunized LEW rats at days 17-22, which was much earlier than days 28-35 in WKY rats. Notably, LEW rats had a GIL CD8α(+)CD11(high) subpopulation after day 17, while WKY rats lacked this population until after day 30. Analyses further revealed a large number of clustered apoptotic CD4(+) or CD3(+) T cells in the glomeruli during recovery (day 23) in LEW rats, as compared to day 35 (transition to fibrosis) in WKY rats. Thus, infiltration of GIL CD8α(+) cells coincided with decline of glomerular inflammation and T cell apoptosis during recovery in LEW rats. Isolated GIL CD8α(+) cells were able to infiltrate glomeruli in both WKY and LEW rats at day 20.

CONCLUSION

Our data revealed a strong association between GIL CD8a+ cells and recovery from early glomerular inflammation. It raises a possibility of involvement of GIL CD8a+ cells in the recovery.

Identification of a bone marrow-derived CD8αα+ dendritic cell-like population in inflamed autoimmune target tissue with capability of inducing T cell apoptosis

DCs play critical roles in promotion of autoimmunity or immune tolerance as potent APCs. In our anti-GBM GN model, WKY rats develop severe T cell-mediated glomerular inflammation followed by fibrosis. A DC-like cell population (CD8αα(+)CD11c(+)MHC-II(+)ED1(-)) was identified in the inflamed glomeruli. Chimera experiments demonstrated that the CD8αα(+) cells were derived from BM. The CD8αα(+) cells infiltrated glomeruli at a late stage (Days 28-35), coincident with a rapid decline in glomerular inflammation before fibrosis. The CD8αα(+) cells isolated from inflamed glomeruli were able to migrate rapidly from the bloodstream into inflamed glomeruli but not into normal glomeruli, suggesting that the migration was triggered by local inflammation. Despite high-level expression of surface and cellular MHC class II molecules, in vitro experiments showed that this CD8αα(+) DC-like cell induced apoptosis but not proliferation in antigen-specific CD4(+) T cells from T cell lines or freshly isolated from lymph nodes; they were not able to do so in the absence of antigens, suggesting induction of apoptosis was antigen-specific. Furthermore, apoptotic T cells were detected in a large number in the glomeruli at Day 32, coincident with the infiltration of the cells into glomeruli, suggesting that the cells may also induce T cell apoptosis in vivo. A potential role of this CD8αα(+) DC-like population in peripheral immune tolerance and/or termination of autoimmune inflammation was discussed.