Compartment specific expression of dendritic cell markers in human glomerulonephritis

Kidney dendritic cell activation is required for progression of renal disease in a mouse model of glomerular injury

The progression of kidney disease to renal failure correlates with infiltration of mononuclear immune cells into the tubulointerstitium. These infiltrates contain macrophages, DCs, and T cells, but the role of each cell type in disease progression is unclear. To investigate the underlying immune mechanisms, we generated transgenic mice that selectively expressed the model antigens ovalbumin and hen egg lysozyme in glomerular podocytes (NOH mice). Coinjection of ovalbumin-specific transgenic CD8+ CTLs and CD4+ Th cells into NOH mice resulted in periglomerular mononuclear infiltrates and inflammation of parietal epithelial cells, similar to lesions frequently observed in human chronic glomerulonephritis. Repetitive T cell injections aggravated infiltration and caused progression to structural and functional kidney damage after 4 weeks. Mechanistic analysis revealed that DCs in renal lymph nodes constitutively cross-presented ovalbumin and activated CTLs. These CTLs released further ovalbumin for CTL activation in the lymph nodes and for simultaneous presentation to Th cells by distinct DC subsets residing in the kidney tubulointerstitium. Crosstalk between tubulointerstitial DCs and Th cells resulted in intrarenal cytokine and chemokine production and in recruitment of more CTLs, monocyte-derived DCs, and macrophages. The importance of DCs was established by the fact that DC depletion rapidly resolved established kidney immunopathology. These findings demonstrate that glomerular antigen-specific CTLs and Th cells can jointly induce renal immunopathology and identify kidney DCs as a mechanistic link between glomerular injury and the progression of kidney disease.

Renal dendritic cells: an update

Discovery into the role of renal dendritic cells (rDCs) in health and disease of the kidney is rapidly accelerating. Progress in deciphering DC precursors and the heterogeneity of monocyte subsets in mice and humans is providing insight into the biology of rDCs. Recent findings have extended knowledge of the origins, anatomy and function of the rDC network at steady state and during periods of injury to the renal parenchyma. This brief review highlights these new findings and provides an update on the study of rDCs.

The early course of kidney allograft rejection: defining the time when rejection begins

We studied the early events in mouse kidney allografts and isografts to define when allorecognition begins and when alloimmune tissue injury begins. Allografts but not isografts showed T-cell infiltration in perivascular areas from day 1, but tubulitis and arteritis did not develop until day 7. Flow cytometry confirmed the early allospecific CD3(+)CD8(+) T-cell infiltrate. At day 1, both allografts and isografts showed extensive transcriptome changes, reflecting the response to surgery, but only allografts showed expression of interferon-gamma (IFN-gamma)-inducible transcripts and T-cell-associated transcripts. Although the number of CD68(+) myeloid cell numbers did not increase in day 1 isografts or allografts, mRNA expression for myeloid markers was increased in isografts and allografts, suggesting activation of resident cells of the macrophage-dendritic cell series (MMDCs) in response to injury, followed by increased CD68(+) cell numbers from day 2. By day 3, an interstitial T-cell and MMDC infiltrate was established in allografts, corresponding with the emergence of allospecific tissue injury, as reflected by decreased parenchymal transcripts. Thus, in renal allografts, allorecognition by T cells occurs in perivascular sites by day 1, but alloimmune parenchymal damage begins at day 3, coinciding with the emergence of the interstitial T-cell-MMDC infiltrate.

Dendritic cells in renal biopsies of patients with ANCA-associated vasculitis

BACKGROUND

Dendritic cells (DCs) maintain immune tolerance and are able to initiate immune responses. Their involvement in ANCA-associated vasculitis (AAV) is unknown. In this study, the participation of DC subsets is investigated in renal biopsies of AAV patients.

METHOD

A total of 25 patients with biopsy-proven AAV and five healthy controls (HC) with normal renal histology were included. Renal biopsies were stained for mature (CD208), immature (CD209), plasmacytoid (CD303) and Langerhans (CD1a) DC subsets. Furthermore, T-cells were stained using a T-cell marker (CD3). The interstitial cellular infiltrate was graded semi-quantitatively from 0+ (= absence of cells) to 3+ (= numerous cells). Within the glomeruli, an absolute count was performed for positive cells.

RESULTS

CD208+ and CD209+ cells were found within patients' glomeruli but not in HC (1 +/- 0.3 versus 0.08 +/- 0.1 cells/glom; 2 +/- 0.3 versus 0.1 +/- 0.07 cells/glom). An average of 0.3 +/- 0.1 cell/glom expressed CD3 in patients while few cells were found in HC (0.1 +/- 0.7 cell/glom). Focal interstitial cellular infiltrates were observed in patients' biopsies but not in HC. Interstitial infiltration with CD3+ and CD209+ cells was assessed at an average of 1+, but some glomeruli and tubuli were surrounded by CD3+ and CD209+ cells forming clusters. Serial sections revealed that CD209+ cells were present in CD3+ rich areas.

CONCLUSION

Both mature and immature glomerular DCs are found in renal biopsies of patients with AAV. Immature DCs cluster with T-cells in interstitial infiltrates in these biopsies. Since DCs form aggregates in T-cell areas, we hypothesize that these cells interact with each other and are involved in lymphoid neogenesis.