Dendritic cells and macrophages in kidney disease

The role of mononuclear phagocyte system in IgA nephropathy: pathogenesis and prognosis

Although the "multiple hits" theory is a widely accepted pathogenesis in IgA nephropathy (IgAN), increasing evidence suggests that the mononuclear/macrophage system plays important roles in the progression of IgAN; however, the exact mechanism is unclear. In the present study, we explored 1,067 patients in 15 studies and found that the number of macrophages per glomerulus was positively related with the degree of hematuria, and the macrophages in the glomeruli were mainly related to mesangial proliferation (M) in renal biopsy. In the tubulointerstitium, macrophages were significantly paralleled to tubulointerstitial α-SMA and NF-kB expression, tubulointerstitial lesion, tubule atrophy/interstitial fibrosis (T), and segmental glomerulosclerosis (S). In the glomeruli and tubulointerstitium, M1 accounted for 85.41% in the M classification according to the Oxford MEST-C, while in the blood, M1 accounted for 100%, and the patients with low CD89⁺ monocyte mean fluorescence intensity displayed more severe pathological characteristics (S1 and T1-2) and clinical symptoms. M1 (CD80⁺) macrophages were associated with proinflammation in the acute phase; however, M2 (CD163⁺) macrophages participated in tissue repair and remodeling, which correlated with chronic inflammation. In the glomeruli, M2 macrophages activated glomerular matrix expansion by secreting cytokines such as IL-10 and tumor necrosis factor-β (TGF-β), and M0 (CD68⁺) macrophages stimulated glomerular hypercellularity. In the tubulointerstitium, M2 macrophages played pivotal roles in renal fibrosis and sclerosis. It is assumed that macrophages acted as antigen-presenting cells to activate T cells and released diverse cytokines to stimulate an inflammatory response. Macrophages infiltrating glomeruli destroy the integrity of podocytes through the mesangio-podocytic-tubular crosstalk as well as the injury of the tubule.

Low intratumor heterogeneity correlates with increased response to PD-1 blockade in renal cell carcinoma

BACKGROUND

Intratumor heterogeneity (ITH) has been shown to be inversely associated with immune infiltration in several cancers including clear cell renal cell carcinoma (ccRCC), but it remains unclear whether ITH is associated with response to immunotherapy (e.g. PD-1 blockade) in ccRCC.

METHODS

We quantified ITH using mutant-allele tumor heterogeneity, investigated the association of ITH with immune parameters in patients with ccRCC (n = 336) as well as those with papillary RCC (pRCC, n = 280) from The Cancer Genome Atlas, and validations were conducted in patients with ccRCC from an independent cohort (n = 152). The relationship between ITH and response to anti-PD-1 immunotherapy was explored in patients with metastatic ccRCC from a clinical trial of anti-PD-1 therapy (n = 35), and validated in three equal-size simulated data sets (n = 60) generated by random sampling with replacement based on this clinical trial cohort.

RESULTS

In ccRCC, low ITH was associated with better survival, more reductions in tumor burden, and clinical benefit of anti-PD-1 immunotherapy through modulating immune activity involving more neoantigens, elevated expression of HLA class I genes, and higher abundance of dendritic cells. Furthermore, we found that the association between the level of ITH and response to PD-1 blockade was independent of the mutation status of PBRM1 and that integrating both factors performed better than the individual predictors in predicting the benefit of anti-PD-1 immunotherapy in ccRCC patients. In pRCC, increased immune activity was also observed in low- versus high-ITH tumors, including higher neoantigen counts, increased abundance of monocytes, and decreased expression of PD-L1 and PD-L2.

CONCLUSIONS

ITH may be helpful in the identification of patients who could benefit from PD-1 blockade in ccRCC, and even in pRCC where no genomic metrics has been found to correlate with response to immune checkpoint inhibitors.

M2a and M2b macrophages predominate in kidney tissues and M2 subpopulations were associated with the severity of disease of IgAN patients

M2 macrophages play important roles during the injury and repair phases in kidney. Our aims are to investigate the distribution of M2 subpopulations and the correlation with clinicopathological features of IgA nephropathy (IgAN) patients. In this study, renal samples from 49 IgAN patients were detected by immunofluorescence. The markers of M2 macrophages, including M2a (CD206+/CD68+), M2b (CD86+/CD68+) and M2c (CD163+/CD68+) were identified. We found M2a and M2b macrophages were the predominant subpopulations in kidney tissues of IgAN. M2a macrophages were mainly distributed in tubulointerstitium with renal lesions like segmental glomerulosclerosis and tubular atrophy/interstitial fibrosis. However, there were larger numbers of M2c in glomeruli with minor lesions. Moreover, M2a and M2c macrophages were inversely correlated with the clinical and pathologic features, respectively. These results suggest M2 subpopulations were involved in the progression of IgAN, and M2a and M2c macrophages might show different properties to participate in the pathogenesis of IgAN.

Respiratory Syncytial Virus Aggravates Renal Injury through Cytokines and Direct Renal Injury

The purpose of this study was to investigate the relationship between renal injury and reinfection that is caused by respiratory syncytial virus (RSV) and to analyze the mechanism of renal injury. Rats were repeatedly infected with RSV on days 4, 8, 14, and 28, then sacrificed and examined on day 56 after the primary infection. Renal injury was examined by transmission electron microscopy and histopathology. The F protein of RSV was detected in the renal tissue by indirect immunofluorescence. Proteinuria and urinary glycosaminoglycans (GAGs), serum levels of albumin, urea nitrogen, and creatinine, secretion of cytokines, T lymphocyte population and subsets, and dendritic cell (DC) activation state were examined. The results showed that renal injury was more serious in the reinfection group than in the primary infection group. At a higher infection dose, 6 × 10⁶ PFU, the renal injury was more severe, accompanied by higher levels of proteinuria and urinary GAGs excretion, and lower levels of serum albumin. Podocyte foot effacement was more extensive, and hyperplasia of mesangial cells and proliferation of mesangial matrix were observed. The maturation state of DCs was specific, compared with the primary infection. There was also a decrease in the ratio of CD4⁺ to CD8⁺ T lymphocytes, due to an increase in the percentage of CD8⁺ T lymphocytes and a decrease in the percentage of CD4⁺ T lymphocytes, and a dramatic increase in the levels of IL-6 and IL-17. In terms of the different reinfection times, the day 14 reinfection group yielded the most serious renal injury and the most significant change in immune function. RSV F protein was still expressed in the glomeruli 56 days after RSV infection. Altogether, these results reveal that RSV infection could aggravate renal injury, which might be due to direct renal injury caused by RSV and the inflammatory lesions caused by the anti-virus response induced by RSV.

Activation of toll-like receptor-7 exacerbates lupus nephritis by modulating regulatory T cells

BACKGROUND

Toll-like receptor-7 (TLR7), which recognizes viral single-stranded RNA, can trigger immune complex glomerulonephritis in experimental lupus erythematosus. However, whether it modulates dendritic cells (DCs) phenotype and regulatory T cells (Treg) function is incompletely understood.

METHOD

Splenocytes and bone marrow DCs were obtained from 5- and 20-week-old female MRL(lpr/lpr) mice and C57BL/6 mice. In addition, to understand the response of Treg and DCs to TLR7 ligation in vivo, 16-week-old female MRL(lpr/lpr) and C57BL/6 mice were distributed into two groups with or without intraperitoneal injections of TLR7 ligand every other day.

RESULTS

After activation with the TLR7 ligand imiquimod in vivo and vitro, DCs from imiquimod-treated MRL/lpr mice showed an altered costimulatory profile, with decreased induction of CD80, CD86, and MHCII expression, comparing to age-matched C57BL/6 control mice. There was no significant difference in the numbers of CD4+CD25+Foxp3+ cells after TLR7 ligation by imiquimod in MRL(lpr/lpr) and control mice. Immunostaining of kidney sections of nephritic MRL/lpr mice revealed that CD11c was expressed in the infiltrated tubulointerstitial cells, and confocal microscopic analysis of renal CD11c+MHCII+, CD11c+CD80+, and CD11c+)CD86+ cells showed an immature phenotype with low levels of CD80, CD86, and MHCII in imiquimod-treated MRL/lpr mice. There was no difference in the number of Foxp3 positive cells in kidneys between the imiquimod and vehicle-treated groups.

CONCLUSIONS

Our results suggest that activation of TLR7 exacerbated lupus nephritis by modulating the abnormally costimulatory phenotype of dendritic cells and functions of Treg in MRL/lpr mice.

Clinicopathological and immunohistological features in childhood IgA nephropathy: a single-centre experience

Background

IgA nephropathy is a glomerular disease diagnosed by renal biopsy and is characterized by a highly variable course ranging from a completely benign condition to rapidly progressive renal failure. We aimed to evaluate the clinical, histopathological and inflammatory characteristics of children with IgA nephropathy.

Methods

Data of 37 patients with IgA nephropathy diagnosed between the years 1980 and 2008 were retrospectively reviewed. Immunohistochemistry was performed in 24 patients. Expression of CD3, CD4, CD8, CD20, CD68, IL-1β, IL-10, IL-17, TGF-β, TNF-α and the newly proposed tubulointerstitial fibrosis marker nestin were evaluated.

Results

The median age at diagnosis was 10 years. Recurrent macroscopic haematuria (66%) was the most common clinical manifestation, and 35% of the patients had synpharyngitic presentation. A significant correlation was found between proteinuria and increase in mesangial matrix (r = 0.406, P = 0.013). The presence of CD4+ T lymphocytes and CD68+ macrophages were also significantly associated with proteinuria >1 g/day. While cytokines IL-1β, IL-10 and TNF-α were mainly expressed in tubular epithelial cells, TGF-β was evident in glomeruli but they had no correlation to clinical features and severity of the disease. Nestin was detected at the tubules in almost half of the patients with no correlation to proteinuria and tubulointersititial fibrosis.

Conclusions

We found a correlation between proteinuria and mesangial matrix expansion. The presence of CD4+ T-lymphocytes and CD68+ macrophages were also significantly associated with proteinuria >1 g/day. Although there are many evidences, for immunological basis of IgA nephropathy, the immunological markers were not fully expressed in children to evaluate glomerular and tubulointerstitial inflammation, and progression of the disease. Further studies with the extended number of children are needed to shed light on the immunological basis of the disease.

A case of secondary focal segmental glomerulosclerosis associated with malignant hypertension

Focal segmental glomerulosclerosis (FSGS) is associated with various clinicopathological conditions, including hypertension. We report here a case of secondary FSGS associated with malignant hypertension. A 33-year-old man with a 1-month history of visual impairment and headache visited the Department of Ophthalmology at our hospital and was found to have hypertensive retinopathy and severe hypertension (230/160 mmHg). He was referred to our department based on suspected renal dysfunction. His blood pressure on admission was 250/130 mmHg. Physical examination and laboratory tests revealed hypertensive cardiac dysfunction, focal brain edema, renal dysfunction (serum creatinine, Cr 7.07 mg/dl, blood urea nitrogen, BUN 49.9 mg/dl), massive proteinuria (10.7 g/day), and thrombotic microangiopathy. Funduscopy showed exudate, hemorrhage, and papilledema. The cause of secondary hypertension could not be identified. He was treated for primary malignant hypertension, but required hemodialysis 3 days after admission due to anuria. Treatment with antihypertensive agents resulted in the gradual recovery of renal function, although heavy proteinuria continued with nephrotic syndrome. Renal biopsy performed 1 month after admission showed features of malignant nephrosclerosis with secondary FSGS. Hemodialysis was discontinued following further improvement in renal function and the most recent laboratory tests showed proteinuria 1.8 g/day and persistent renal dysfunction (BUN 36.5 mg/dl, Cr 3.14 mg/dl). Malignant hypertension may cause various injuries, including glomerular endothelial and epithelial cell injuries in glomerular hypertension and hyperfiltration, increase of the renin-angiotensin-aldosterone system, and endothelial-epithelial interaction, resulting in the development of secondary FSGS and heavy proteinuria.

Alteration of embryonic AT(2)-R and inflammatory cytokines gene expression induced by prenatal exposure to lipopolysaccharide affects renal development

Prenatal exposure to LPS(lipopolysaccharide) results in renal damage in offspring rats, but the mechanism is unknown. The present study was to explore the role of angiotensin II and inflammation in the development of renal damage induced by prenatal exposure to LPS. The pregnant rats were randomly divided into two groups, i.e., control group, LPS group. The rats in the two groups were administered intraperitoneally with vehicle or 0.79 mg/kg LPS on 8th, 10th and 12th day during gestation. The mRNA expression of angiotensinogen, renin, AT(1)-R, AT(2)-R, TNF-α and IL-6 in embryos were assessed. Renal Ang II-positive cells, monocytes/macrophages, lymphocytes, collagen I and TUNEL-positive cells were identified by immunohistochemical staining in newborn and 7-week-old offspring rats. The number of glomeruli and creatinine clearance rate were determined in offspring at 7 weeks of age. The results showed that prenatal LPS decreased AT(2)-R mRNA expression but increased TNF-α and IL-6 mRNA expression in embryos. Prenatal LPS decreased renal angiotensin II-positive cells in newborn offspring rats, while these increased in 7-week-old offspring rats. Prenatal LPS decreased glomerular number and creatinine clearance rate but increased renal infiltrating monocytes/macrophages and lymphocytes at 7 weeks of age. Prenatal LPS also increased TUNEL-positive cells and collagen I expressions in newborn rats and 7-week-old offspring rats.

CONCLUSION

Alteration of embryonic AT(2)-R and inflammatory cytokines gene expression induced by prenatal exposure to lipopolysaccharide affects renal development.

Dendritic cells in experimental renal inflammation--Part I

Dendritic cells (DCs) are bone marrow-derived professional antigen-presenting cells that act as master regulators of acquired and innate immune responses. While descriptions of cells with dendritic morphology in rodent kidneys date back to the early 1970s, a network of DCs in the mouse kidney has only recently been described. DCs acquire distinct phenotypic and functional characteristics depending on the microenvironment and the disease stages. Concomitantly, their communication with cells of the adaptive immunity might have tissue-protective or tissue-deleterious consequences. This review summarizes results from recent studies on the role of DCs in experimental renal inflammation.

Glomerular hemophagocytic macrophages in a patient with proteinuria and clinical and laboratory features of hemophagocytic lymphohistiocytosis (HLH)

Hemophagocytic lymphohistiocytosis (HLH) is a heterogeneous disorder characterized by excessive activation and proliferation of nonmalignant histiocytes, which are commonly found in bone marrow, lymph nodes, spleen and liver in affected patients. Here, we report the presence of glomerular macrophages, including one showing erythrophagocytosis, on renal biopsy in a 25-year-old patient with clinical presentation and laboratory changes consistent with HLH. The clinical course was marked by persistent fever for 2 months, pleural and pericardial effusion, splenomegaly, lymphadenopathy, pancytopenia, cardiac arrhythmias, multiple organ dysfunction, and proteinuria, with demise after a 2-month hospitalization. Positive assay for Epstein-Barr virus (EBV), marked hyperferritinemia, hypofibrinogenemia, hypertriglyceridemia, elevated anti-nuclear antibody, proteinuria, and decreased circulating NK cells by flow cytometry were compatible with the diagnosis of HLH. We suggest that the glomerular hemophagocytic macrophages, which have not heretofore been described in the kidney of a patient with HLH, may have contributed to renal dysfunction manifest as proteinuria.

High circulating levels of interleukin-18 binding protein indicate the severity of glomerular involvement in systemic lupus erythematosus

In systemic lupus erythematosus (SLE), glomerular involvement often progresses with the activity of the disease. Immune complexes and abnormal secretion of cytokines are thought to be involved in the central mechanism of the development of lupus nephritis. We investigated serum levels of interleukin 18 (IL-18), a proinflammatory cytokine, and its natural antagonist IL-18 binding protein (IL-18 BP) in 45 patients with lupus nephritis. IL-18 levels were significantly increased in patients with Class II, Class III, and Class IV lupus nephritis compared with the level in a healthy control group. However, the levels stayed within the non-significant range in Class V. IL-18 BP levels were significantly increased in patients with Class III and Class IV lupus nephritis, in which histological activity and chronicity are severe. However, IL-18 BP levels stayed within the non-significant range in Class II and Class V, in which histological markers are mild. We also compared the levels of IL-18 and IL-18 BP in patients with and without glomerular infiltration of inflammatory cells. IL-18 was increased regardless of glomerular infiltration. However, IL-18 BP was increased only in patients with glomerular infiltration. These data suggest that IL-18 levels indicate the extent of the offending inflammatory response not only in the bloodstream but also in renal tissue, and that high IL-18 BP levels indicate the severity of existing glomerular injury.