IL-18 Has IL-12-Independent Effects in Delayed-Type Hypersensitivity: Studies in Cell-Mediated Crescentic Glomerulonephritis

Abstract

IL-18 (formerly known as IFN-γ-inducing factor) enhances Th1 responses via effects that are thought to be dependent on and synergistic with IL-12. The potential for IL-18 to exert IL-12-independent effects in delayed-type hypersensitivity (DTH) responses was studied in a model of Th1-directed, DTH-mediated crescentic glomerulonephritis induced by planting an Ag in glomeruli of sensitized mice as well as in cutaneous DTH. Sensitized genetically normal (IL-12+/+) mice developed proteinuria and crescentic glomerulonephritis with a glomerular influx of DTH effectors (CD4+ T cells, macrophages, and fibrin deposition) in response to the planted glomerular Ag. IL-12p40-deficient (IL-12−/−) mice showed significant reductions in crescent formation, proteinuria, and glomerular DTH effectors. Administration of IL-18 to IL-12−/− mice restored the development of histological (including effectors of DTH) and functional glomerular injury in IL-12−/− mice to levels equivalent to those in IL-12+/+ mice. IL-18 administration to IL-12−/− mice increased glomerular ICAM-1 protein expression, but did not restore Ag-stimulated splenocyte IFN-γ, GM-CSF, IL-2, or TNF-α production. Sensitized IL-12+/+ mice also developed cutaneous DTH following intradermal challenge with the nephritogenic Ag. Cutaneous DTH was inhibited in IL-12−/− mice, but was restored by administration of IL-18. IL-12+/+ mice given IL-18 developed augmented injury, with enhanced glomerular and cutaneous DTH, demonstrating the synergistic effects of IL-18 and IL-12 in DTH responses. These studies demonstrate that even in the absence of IL-12, IL-18 can induce in vivo DTH responses and up-regulate ICAM-1 without inducing IFN-γ, GM-CSF, or TNF-α production.

Toll‐like receptor 2 induces Th17 myeloperoxidase autoimmunity while Toll‐like receptor 9 drives Th1 autoimmunity in murine vasculitis

“…The sequence for the immunostimulatory CpG ODN was TCCAT-GACGTTCCTGACGTT (5Ј-3Ј) bound with phosphothioate linkages. Sheep anti-mouse GBM antibody was generated as previously described (20). Anti-IFN␥ monoclonal antibody (mAb) R4-6A2 (ATCC), was grown and purified in-house, and anti-interleukin-17A (anti-IL-17A; mAb 421) was purchased from R&D Systems.…”

“…Using an aseptic technique, a single-cell suspension of mouse splenocytes (4 ϫ 10 6 cells/ml) was cultured in RPMI/10% fetal calf serum with recombinant mouse MPO (10 g/ml) at 37°C for 72 hours. IFN␥, IL-2, IL-4, and IL-17A concentrations were measured by enzyme-linked immunosorbent assay (ELISA) as previously described (20). The following antibodies were used: rat anti-mouse IFN␥ (R4-6A2; BD PharMingen), biotinylated rat anti-mouse IFN␥ (XMG1.2; BD PharMingen), rat antimouse IL-4 (11B11; ATCC), biotinylated rat anti-mouse IL-4 (BVD6; DNAX Research Institute), rat anti-mouse IL-2 (JES6-1A12, DNAX Research Institute), and biotinylated anti-mouse IL-2 (JES6-5H4, DNAX Research Institute).…”

IL-12p40 and IL-18 in Crescentic Glomerulonephritis

“…For cytokine production, splenocytes from mice with GN were cultured for 72 h with 10 g/ml normal sheep IgG. IFN-␥, IL-4, IL-1␤, TNF, and GM-CSF in supernatants were measured by ELISA as described previously (16). IL-5 was measured by ELISA using the rat anti-mouse IL-5 mAb TRFK5 (0.5 g/ml; R&D Systems, Minneapolis, MN) for capture and biotinylated TRFK4 (100 ng/ml; R&D Systems) for detection, with rmIL-5 as a standard (R&D Systems) and streptavidin-horseradish peroxidase (HRP; 1:1000; Chemicon, Boronia, Victoria, Australia).…”

“…IL-18, originally described as IFN-␥-inducing factor (21), both is a co-factor for IFN-␥ and other Th1 cytokine production and induces expression of leukocyte chemoattractants and adhesion molecules (16,22). Exogenous IL-18 can enhance immune responses and increase the severity of experimental crescentic GN (16), independent of IL-12p40. Intrarenal IL-18 expression has been documented in murine lupus nephritis (23), rat experimental crescentic GN (24), and experimental ischemia reperfusion injury (25), playing a functional role in the last disease (26).…”

“…Although there is some overlap in their biologic effects, studies in experimental autoimmune encephalomyelitis (EAE) have shown that whereas IL-12 primes cells for IFN-␥ production, IL-23 has significant proinflammatory effects on both memory T cells and macrophages (20). IL-18, originally described as IFN-␥-inducing factor (21), both is a co-factor for IFN-␥ and other Th1 cytokine production and induces expression of leukocyte chemoattractants and adhesion molecules (16,22). Exogenous IL-18 can enhance immune responses and increase the severity of experimental crescentic GN (16), independent of IL-12p40.…”