Programmed Death 1 Ligand (PD-L) 1 and PD-L2 Limit Autoimmune Kidney Disease: Distinct Roles

Abstract

The programmed death 1/programmed death 1 ligand (PD-L) pathway is instrumental in peripheral tolerance. Blocking this pathway exacerbates experimental autoimmune diseases, but its role in autoimmune kidney disease has not been explored. Therefore, we tested the hypothesis that the programmed death 1 ligands (PD-L1 and PD-L2), provide a protective barrier during T cell- and macrophage (Mφ)-dependent autoimmune kidney disease. For this purpose, we compared nephrotoxic serum nephritis (NSN) in mice lacking PD-L1 (PD-L1−/−), PD-L2 (PD-L2−/−), or both (PD-L1/L2−/−) to wild-type (WT) C57BL/6 mice. Kidney pathology, loss of renal function, and intrarenal leukocyte infiltrates were increased in each PD-L−/− strain as compared with WT mice. Although the magnitude of renal pathology was similar in PD-L1−/− and PD-L2−/− mice, our findings suggest that kidney disease in each strain is regulated by distinct mechanisms. Specifically, we detected increased CD68+ cells along with elevated circulating IgG and IgG deposits in glomeruli in PD-L2−/− mice, but not PD-L1−/− mice. In contrast, we detected a rise in activated CD8+ T cells in PD-L1−/− mice, but not PD-L2−/− mice. Furthermore, since PD-L1 is expressed by parenchymal and hemopoietic cells in WT kidneys, we explored the differential impact of PD-L1 expression on these cell types by inducing NSN in bone marrow chimeric mice. Our results indicate that PD-L1 expression on hemopoietic cells, and not parenchymal cells, is primarily responsible for limiting leukocyte infiltration during NSN. Taken together, our findings indicate that PD-L1 and PD-L2 provide distinct negative regulatory checkpoints poised to suppress autoimmune renal disease.

Circulating CSF-1 Promotes Monocyte and Macrophage Phenotypes that Enhance Lupus Nephritis

“…41 To identify ␤-galactosidase encoded by lacZ (CSF-1 expression), we treated frozen kidney sections as described previously. 20 …”

“…Antigen retrieval was performed by immersion in citrate buffer followed by blocking endogenous peroxidase activity and nonspecific binding of avidin and biotin as described previously. 41 We incubated these sections with a primary antibody, goat anti-human CSF-1 antibody (N-16; Santa Cruz, CA), and we detected the primary antibody by incubation with biotinylated rabbit anti-goat Ab followed by development with 3Ј3-diaminobenzidine (Vector; Burlingame, CA). We verified staining specificity by replacing the primary antibody with goat IgG (eBioscience, San Diego, CA) and by preabsorbing with peptide for CSF-1 antibody (Santa Cruz).…”

“…We sacrificed these mice after 24 and 48 h and prepared the kidney and blood samples to detect EGFP ϩ cells using flow cytometry as described previously. 41 We adoptively transferred EGFP ϩ BM cells into Csf-1 op/op ;MRL-Fas lpr mice. These mice were then injected with rCSF-1 (50 g/kg body wt) every 12 h, and sacrificed after 24 and 48 h.…”

Distinct Roles of CSF-1 Isoforms in Lupus Nephritis

“…28 caspase-3 Ab (Asp175; Cell -signaling, MA). 47 The number of cells bearing CD4, CD8, and CD68 determinants and apoptotic cells was assessed in ten randomly selected high-power fields. We determined intrarenal Mø proliferation by dual staining.…”

Effects of Anti-B7.1/B7.2 Antibodies on LPS-Stimulated Macrophages

“…PD-L1 molecules are ubiquitously expressed on many immunological cells, including macrophages. Although a number of studies suggest an inhibitory role of PD-L1 on activating T-cells, less is known about the expression and function of PD-L2 (Menke et al, 2007). In the present study, we examined the effects of anti-B7.1/B7.2 antibodies on the production of pro-inflammatory cytokines and nitric oxide, and the expression of co-stimulatory molecules in LPS-stimulated macrophages.…”