Dendritic cells in experimental renal inflammation--Part I

Histological Correlation between Tonsillar and Glomerular Lesions in Patients with IgA Nephropathy Justifying Tonsillectomy: A Retrospective Cohort Study

Tonsillectomy with steroid pulse therapy (SPT) has been established as an effective treatment for immunoglobulin A nephropathy (IgAN) in Japan. However, the underlying mechanisms supporting tonsillectomy remain unclear. This study assessed palatine tonsils from 77 patients with IgAN, including 14 and 63 who received SPT before and after tonsillectomy, respectively. Tonsils from 21 patients with chronic tonsillitis were analyzed as controls. Specific tonsillar lesions were confirmed in patients with IgAN, correlating with active or chronic renal glomerular lesions and SPT. T-nodule and involution of lymphoepithelial symbiosis scores in tonsils correlated with the incidence of active crescents and segmental sclerosis in the glomeruli, respectively. The study revealed an essential role of the tonsil-glomerular axis in early active and late chronic phases. Moreover, the SPT-preceding group demonstrated no changes in the T-nodule score, which correlated with active crescent formation, but exhibited a considerable shrinkage of lymphatic follicles that produced aberrant IgA1. The study underscores the involvement of innate and cellular immunity in IgAN and advocates for tonsillectomy as a necessary treatment alongside SPT for IgAN, based on a stepwise process.

Glomerular Macrophages in Human Auto- and Allo-Immune Nephritis

Macrophages are involved in tissue homeostasis. They participate in inflammatory episodes and are involved in tissue repair. Macrophages are characterized by a phenotypic heterogeneity and a profound cell plasticity. In the kidney, and more particularly within glomeruli, macrophages are thought to play a maintenance role that is potentially critical for preserving a normal glomerular structure. Literature on the glomerular macrophage role in human crescentic glomerulonephritis and renal transplantation rejection with glomerulitis, is sparse. Evidence from preclinical models indicates that macrophages profoundly modulate disease progression, both in terms of number-where depletion has resulted in a reduced glomerular lesion-and sub-phenotype-M1 being more profoundly detrimental than M2. This evidence is corroborated by better outcomes in patients with a lower number of glomerular macrophages. However, due to the very limited biopsy sample size, the type and role of macrophage subpopulations involved in human proliferative lesions is more difficult to precisely define and synthesize. Therefore, specific biomarkers of macrophage activation may enhance our ability to assess their role, potentially enabling improved monitoring of drug activity and ultimately allowing the development of novel therapeutic strategies to target these elusive cellular players.

Flt3 inhibition alleviates chronic kidney disease by suppressing CD103+ dendritic cell-mediated T cell activation

BACKGROUND

Chronic kidney disease (CKD) is a global public health problem, which lacks effective treatment. Previously, we have shown that CD103+ dendritic cells (DCs) are pathogenic in adriamycin nephropathy (AN), a model of human focal segmental glomerulosclerosis (FSGS). Fms-like tyrosine kinase 3 (Flt3) is a receptor that is expressed with high specificity on tissue resident CD103+ DCs.

METHODS

To test the effect on CD103+ DCs and kidney injury of inhibition of Flt3, we used a selective Flt3 inhibitor (AC220) to treat mice with AN.

RESULTS

Human CD141+ DCs, homologous to murine CD103+ DCs, were significantly increased in patients with FSGS. The number of kidney CD103+ DCs, but not CD103- DCs or plasmacytoid DCs, was significantly decreased in AN mice after AC220 administration. Treatment with AC220 significantly improved kidney function and reduced kidney injury and fibrosis in AN mice. AC220-treated AN mice had decreased levels of inflammatory cytokines and chemokines, tumor necrosis factor-α, interleukin (IL)-1β, IL-6, CCL2 and CCL5 and reduced kidney infiltration of CD4 T cells and CD8 T cells. The protective effect of AC220 was associated with its suppression of CD103+ DCs-mediated CD8 T cell proliferation and activation in AN mice.

CONCLUSION

Flt3 inhibitor AC220 effectively reduced kidney injury in AN mice, suggesting that this inhibitor might be a useful pharmaceutical agent to treat CKD.

Myeloid and Plasmacytoid Dendritic Cells and Cancer - New Insights

Dendritic cells (DCs) use effective mechanisms to combat antigens and to bring about adaptive immune responses through their ability to stimulate näive T cells. At present, four major cell types are categorised as DCs: Classical or conventional (cDCs), Plasmacytoid (pDCs), Langerhans cells (LCs), and monocyte-derived DCs (Mo-DCs). It was suggested that pDCs, CD1c+ DCs and CD141+ DCs in humans are equivalent to mouse pDCs, CD11b+ DCs and CD8α+ DCs, respectively. Human CD141+ DCs compared to mouse CD8α+ DCs have remarkable functional and transcriptomic similarities. Characteristic markers, transcription factors, toll-like receptors, T helpers (Th) polarisation, cytokines, etc. of DCs are discussed in this review. Major histocompatibility complex (MHC) I and II antigen presentation, cross-presentation and Th polarisation are defined, and the dual role of DCs in the tumour is discussed. Human DCs are the main immune cells that orchestrate the immune response in the tumour microenvironment.

Renal Macrophages and Dendritic Cells in SLE Nephritis

PURPOSE OF REVIEW

The purpose of the study was to review the characteristics of renal macrophages and dendritic cells during homeostasis and disease, with a particular focus on lupus nephritis.

RECENT FINDINGS

Resident renal macrophages derive from embryonic sources and are long-lived and self-renewing; they are also replaced from the bone marrow with age. The unique characteristics of macrophages in each tissue are imposed by the microenvironment and reinforced by epigenetic modifications. In acute renal injury, inflammatory macrophages are rapidly recruited and then replaced by those with a wound healing/resolution phenotype. In lupus nephritis, dendritic cells infiltrate the kidneys and function to present antigen and organize tertiary lymphoid structures that amplify inflammation. In addition, both infiltrating and resident macrophages contribute to ongoing injury. These cells have a mixed inflammatory and alternatively activated phenotype that may reflect failed resolution, potentially leading to tissue fibrosis and irreversible damage. A further understanding of the renal inflammatory cells that mediate tissue injury and fibrosis should lead to new therapies to help preserve renal function in patients with lupus nephritis.

A systems approach to renal inflammation in SLE

Lupus disease and its complications including lupus nephritis (LN) are very disabling and significantly impact the quality of life and longevity of patients. Broadly immunosuppressive treatments do not always provide the expected clinical benefits and have significant side effects that contribute to patient morbidity. In the era of systems biology, new strategies are being deployed integrating diverse sources of information (molecular and clinical) so as to identify individual disease specificities and select less aggressive treatments. In this review, we summarize integrative approaches linking molecular disease profiles (mainly tissue transcriptomics) and clinical phenotypes. The main goals are to better understand the pathogenesis of lupus nephritis, to identify the risk factors for renal flare and to find the predictors of both short and long-term clinical outcome. Identification of common key drivers and additional patient-specific key drivers can open the door to improved and individualized therapy to prevent and treat LN.

Immune Cells and Inflammation in Diabetic Nephropathy

Diabetic nephropathy (DN) is a serious complication of diabetes. At its core, DN is a metabolic disorder which can also manifest itself in terms of local inflammation in the kidneys. Such inflammation can then drive the classical markers of fibrosis and structural remodeling. As a result, resolution of immune-mediated inflammation is critical towards achieving a cure for DN. Many immune cells play a part in DN, including key members of both the innate and adaptive immune systems. While these cells were classically understood to primarily function against pathogen insult, it has also become increasingly clear that they also serve a major role as internal sensors of damage. In fact, damage sensing may serve as the impetus for much of the inflammation that occurs in DN, in a vicious positive feedback cycle. Although direct targeting of these proinflammatory cells may be difficult, new approaches that focus on their metabolic profiles may be able to alleviate DN significantly, especially since dysregulation of the local metabolic environment may well be responsible for triggering inflammation to begin with. In this review, the authors consider the metabolic profile of several relevant immune types and discuss their respective roles.

CD103+ Dendritic Cells Elicit CD8+ T Cell Responses to Accelerate Kidney Injury in Adriamycin Nephropathy

CD103(+) dendritic cells (DCs) in nonlymphoid organs exhibit two main functions: maintaining tolerance by induction of regulatory T cells and protecting against tissue infection through cross-presentation of foreign antigens to CD8(+) T cells. However, the role of CD103(+) DCs in kidney disease is unknown. In this study, we show that CD103(+) DCs are one of four subpopulations of renal mononuclear phagocytes in normal kidneys. CD103(+) DCs expressed DC-specific surface markers, transcription factors, and growth factor receptors and were found in the kidney cortex but not in the medulla. The number of kidney CD103(+) DCs was significantly higher in mice with adriamycin nephropathy (AN) than in normal mice, and depletion of CD103(+) DCs attenuated kidney injury in AN mice. In vitro, kidney CD103(+) DCs preferentially primed CD8(+) T cells and did not directly induce tubular epithelial cell apoptosis. Adoptive transfer of CD8(+) T cells significantly exacerbated kidney injury in AN SCID mice, whereas depletion of CD103(+) DCs in these mice impaired activation and proliferation of transfused CD8(+) T cells and prevented the exacerbation of kidney injury associated with this transfusion. In conclusion, kidney CD103(+) DCs display a pathogenic role in murine CKD via activation of CD8(+) T cells.

Structure and function of renal macrophages and dendritic cells from lupus-prone mice

OBJECTIVE

To characterize renal macrophages and dendritic cells (DCs) in 2 murine models of lupus nephritis.

METHODS

We used a bead-based enrichment step followed by cell sorting to isolate populations of interest from young mice and nephritic mice. Cell morphology was examined by microscopy. Arginase and nitrite production was examined using biochemical assays. The antigen-presenting functions of the cells were determined using mixed lymphocyte reactions. Selected cytokine, chemokine, and Toll-like receptor (TLR) profiles were examined using real-time quantitative polymerase chain reaction.

RESULTS

We identified 2 populations of macrophages and 3 populations of DCs in both of our murine models of lupus (NZB/NZW and [NZW × BXSB]F1 mice). F4/80(high) macrophages, which were resident in normal kidneys and found to be increased in number during nephritis, did not produce either arginase or nitrite upon cytokine stimulation and acquired a mixed proinflammatory and antiinflammatory functional phenotype during nephritis that resembles the constitutively activated phenotype of gut F4/80(high) macrophages. The various cell types differed in their expression of chemokine receptors and TLRs, consistent with variability in their renal location. Resident renal CD103+ DCs were the best antigen-presenting cells and could easily be distinguished from CD11c(high) myeloid DCs that accumulated in large numbers during nephritis.

CONCLUSION

Our study highlights the heterogeneity of the macrophage/DC infiltrate in chronic lupus nephritis and provides an initial phenotypic and functional analysis of the different cellular components that can now be used to define the role of each cell subset in nephritis progression or amelioration. Of note, the dominant macrophage population that accumulates during nephritis has an acquired phenotype that is neither M1 nor M2 and may reflect failure of resolution of inflammation.

Increased tubulointerstitial recruitment of human CD141(hi) CLEC9A(+) and CD1c(+) myeloid dendritic cell subsets in renal fibrosis and chronic kidney disease

Dendritic cells (DCs) play critical roles in immune-mediated kidney diseases. Little is known, however, about DC subsets in human chronic kidney disease, with previous studies restricted to a limited set of pathologies and to using immunohistochemical methods. In this study, we developed novel protocols for extracting renal DC subsets from diseased human kidneys and identified, enumerated, and phenotyped them by multicolor flow cytometry. We detected significantly greater numbers of total DCs as well as CD141(hi) and CD1c(+) myeloid DC (mDCs) subsets in diseased biopsies with interstitial fibrosis than diseased biopsies without fibrosis or healthy kidney tissue. In contrast, plasmacytoid DC numbers were significantly higher in the fibrotic group compared with healthy tissue only. Numbers of all DC subsets correlated with loss of kidney function, recorded as estimated glomerular filtration rate. CD141(hi) DCs expressed C-type lectin domain family 9 member A (CLEC9A), whereas the majority of CD1c(+) DCs lacked the expression of CD1a and DC-specific ICAM-3-grabbing nonintegrin (DC-SIGN), suggesting these mDC subsets may be circulating CD141(hi) and CD1c(+) blood DCs infiltrating kidney tissue. Our analysis revealed CLEC9A(+) and CD1c(+) cells were restricted to the tubulointerstitium. Notably, DC expression of the costimulatory and maturation molecule CD86 was significantly increased in both diseased cohorts compared with healthy tissue. Transforming growth factor-β levels in dissociated tissue supernatants were significantly elevated in diseased biopsies with fibrosis compared with nonfibrotic biopsies, with mDCs identified as a major source of this profibrotic cytokine. Collectively, our data indicate that activated mDC subsets, likely recruited into the tubulointerstitium, are positioned to play a role in the development of fibrosis and, thus, progression to chronic kidney disease.

Cross-species transcriptional network analysis defines shared inflammatory responses in murine and human lupus nephritis

Lupus nephritis (LN) is a serious manifestation of systemic lupus erythematosus. Therapeutic studies in mouse LN models do not always predict outcomes of human therapeutic trials, raising concerns about the human relevance of these preclinical models. In this study, we used an unbiased transcriptional network approach to define, in molecular terms, similarities and differences among three lupus models and human LN. Genome-wide gene-expression networks were generated using natural language processing and automated promoter analysis and compared across species via suboptimal graph matching. The three murine models and human LN share both common and unique features. The 20 commonly shared network nodes reflect the key pathologic processes of immune cell infiltration/activation, endothelial cell activation/injury, and tissue remodeling/fibrosis, with macrophage/dendritic cell activation as a dominant cross-species shared transcriptional pathway. The unique nodes reflect differences in numbers and types of infiltrating cells and degree of remodeling among the three mouse strains. To define mononuclear phagocyte-derived pathways in human LN, gene sets activated in isolated NZB/W renal mononuclear cells were compared with human LN kidney profiles. A tissue compartment-specific macrophage-activation pattern was seen, with NF-κB1 and PPARγ as major regulatory nodes in the tubulointerstitial and glomerular networks, respectively. Our study defines which pathologic processes in murine models of LN recapitulate the key transcriptional processes active in human LN and suggests that there are functional differences between mononuclear phagocytes infiltrating different renal microenvironments.

Dendritic cells in human renal inflammation--Part II

Dendritic cells (DCs) are bone marrow-derived professional antigen-presenting cells that act as master regulators of acquired and innate immune responses. Here, we review the available information on their role in human renal inflammation. In the 1980s and early 1990s, major histocompatibility complex class II antigen- (HLA-DR) positive DCs were first described in normal human kidneys and in the interstitium of kidneys from patients with glomerulonephritis. Several DC subtypes were subsequently distinguished based on their expression of CD1c/BDCA-1, CD141/BDCA-3 and CD209/DC-SIGN (in combination with HLA-DR). These cells were almost exclusively found in the tubulointerstitium, with increased numbers seen during glomerulonephritis. It appears that the human renal tubulointerstitium harbors different DC types which allow the collection of both exogenous as well as endogenous antigens. Plasmacytoid DCs have a plasma cell-like morphology and were commonly found within nodular tubulointerstitial infiltrates. Follicular DCs are rarely seen, but show a predominant localization in organized infiltrates. CD207/langerin is a marker for Langerhans cells. Langerin-positive cells have been found in association with the collecting ducts and urothelium. A functional characterization of these subtypes has been hampered by the difficulty of obtaining samples for analysis. However, these studies are clearly required to define the role of DCs and DC subsets in the pathophysiology of renal disease.