Toll-like receptor-7 modulates immune complex glomerulonephritis

Viral infections may trigger immune complex glomerulonephritis via Toll-like receptors (TLR), as certain TLR trigger immunity upon recognition of viral nucleic acids. On the basis of previous findings regarding viral double-stranded RNA and TLR3 in experimental lupus erythematosus, a similar role for TLR7 that recognizes viral single-stranded RNA was hypothesized. Immunostaining of kidney sections of nephritic MRLlpr/lpr mice revealed TLR7 expression in infiltrating ER-HR3-positive macrophages and few CD11c-positive dendritic cells but not in glomerular mesangial cells as observed for TLR3. This finding was consistent with the distribution pattern of intravenously injected single-stranded RNA in nephritic MRLlpr/lpr mice. TLR7 ligation activated monocytes and dendritic cells, both isolated from MRLlpr/lpr mice, to secrete IFN-alpha, IL-12p70, IL-6, and CCL2. In vivo, a single injection of the TLR7 ligand imiquimod increased serum levels of IL-12p70, IFN-alpha, and IL-6. A course of 25 microg of imiquimod given every other day from week 16 to 18 of age aggravated lupus nephritis in MRLlpr/lpr mice. This was associated with increased glomerular immune complex deposits as well as interstitial expression of CCL2 in imiquimod-treated MRLlpr/lpr mice. Different types of viral nucleic acids seem to modulate systemic autoimmunity through specific interactions with their respective TLR. Different TLR expression profiles on immune cell subsets and nonimmune parenchymal cell types determine the molecular mechanisms involved in viral infection-associated exacerbation of lupus nephritis and possibly other types of immune complex glomerulonephritis.     

TLR4 links podocytes with the innate immune system to mediate glomerular injury

Toll-like receptors (TLR) classically recognize pathogen-associated danger signals but are also activated via endogenous ligands. For evaluation of their role in inflammatory kidney disease, the function of TLR was analyzed in two mouse models of cryoglobulinemic membranoproliferative glomerulonephritis (MPGN; mice transgenic for thymic stromal lymphopoietin [TSLP], with or without deletion of the Fcgamma receptor IIb). Expression of TLR1 through 9 and TLR11 mRNA was detectable in whole kidneys and in isolated glomeruli of wild-type mice, with TLR3 and TLR4 having the highest absolute levels of expression. TLR1, 2, and 4 were increased in TSLP transgenic mice and even higher in TSLP transgenic FcgammaRIIb-deficient mice. TLR5 through 9 and 11 were upregulated to similar degrees in TSLP transgenic and TSLP transgenic FcgammaRIIb-deficient mice. Immunohistochemical studies of nephritic glomeruli localized TLR4 protein to podocytes. Cultured podocytes also expressed TLR4, and stimulation with TLR4-specific ligands resulted in a marked induction of chemokines; this was reduced by specific knockdown of TLR4 with siRNA. Fibrinogen, a potential endogenous TLR4 ligand, was shown to induce a similar profile of chemokines. In conclusion, it was demonstrated that TLR4 is constitutively expressed by podocytes and is upregulated in MPGN, where it may mediate glomerular injury by modulating expression of chemokines; therefore, TLR4 may link podocytes with the innate immune system to mediate MPGN triggered by the deposition of immune complexes.     

Viral double-stranded RNA aggravates lupus nephritis through Toll-like receptor 3 on glomerular mesangial cells and antigen-presenting cells

How viral infections trigger autoimmunity is poorly understood. A role for Toll-like receptor 3 (TLR3) was hypothesized in this context as viral double-stranded RNA (dsRNA) activates dendritic cells to secrete type I interferons and cytokines that are known to be associated with the disease activity in systemic lupus erythematosus (SLE). Immunostaining of nephritic kidney sections of autoimmune MRL(lpr/lpr) mice revealed TLR3 expression in infiltrating antigen-presenting cells as well as in glomerular mesangial cells. TLR3-positive cultured mesangial cells that were exposed to synthetic polyinosinic-cytidylic acid (pI:C) RNA in vitro produced CCL2 and IL-6. pI:C RNA activated macrophages and dendritic cells, both isolated from MRL(lpr/lpr) mice, to secrete multiple proinflammatory factors. In vivo, a single injection of pI:C RNA increased serum IL-12p70, IL-6, and IFN-alpha levels. A course of 50 microg of pI:C RNA given every other day from weeks 16 to 18 of age aggravated lupus nephritis in pI:C-treated MRL(lpr/lpr) mice. Serum DNA autoantibody levels were unaltered upon systemic exposure to pI:C RNA in MRL(lpr/lpr) mice, as pI:C RNA, in contrast to CpG-DNA, failed to induce B cell activation. It therefore was concluded that viral dsRNA triggers disease activity of lupus nephritis by mechanisms that are different from those of bacterial DNA. In contrast to CpG-DNA/TLR9 interaction, pI:C RNA/TLR3-mediated disease activity is B cell independent, but activated intrinsic renal cells, e.g., glomerular mesangial cells, to produce cytokines and chemokines, factors that can aggravate autoimmune tissue injury, e.g., lupus nephritis.     

Bacterial CpG-DNA aggravates immune complex glomerulonephritis: role of TLR9-mediated expression of chemokines and chemokine receptors

Immune complex glomerulonephritis (GN) often deteriorates during infection with viruses and bacteria that, in contrast to mammals, have DNA that contains many unmethylated CpG motifs. Balb/c mice with horse apoferritin-induced GN (HAF-GN) were treated with either saline, CpG-oligodeoxynucleotides (ODN), or control GpC-ODN. Only CpG-ODN exacerbated HAF-GN with an increase of glomerular macrophages, which was associated with massive albuminuria and increased renal MCP-1/CCL2, RANTES/CCL5, CCR1, CCR2, and CCR5 mRNA expression. CpG-ODN induced a Th1 response as indicated by serum anti-HAF IgG(2a) titers, mesangial IgG(2a) deposits, and splenocyte IFN-gamma secretion. Messenger RNA for the CpG-DNA receptor Toll-like reeptor 9 (TLR9) was present in kidneys with HAF-GN but not in normal kidneys. The source of TLR9 mRNA in HAF-GN could be infiltrating macrophages or intrinsic renal cells, e.g., mesangial cells; but, in vitro, only murine J774 macrophages expressed TLR9. In J774 cells, CpG-ODN induced the chemokines MCP-1/CCL2 and RANTES/CCL5 and the chemokine receptors CCR1 and CCR5. It is concluded that CpG-DNA can aggravate preexisting GN via a shift toward a Th1 response but also by a novel pathway involving TLR9-mediated chemokine and chemokine receptor expression by macrophages, which may contribute to the enhanced glomerular macrophage recruitment and activation. This mechanism may be relevant during infection-triggered exacerbation of human immune-complex GN and other immune-mediated diseases in general.     

IFN-gamma mediates crescent formation and cell-mediated immune injury in murine glomerulonephritis

Features of crescentic glomerulonephritis suggest that it results from a T helper 1 (Th1) nephritogenic immune response. Interferon-gamma (IFN-gamma), produced by Th1 cells, is involved in T cell-directed macrophage activation in effector Th1 responses. The hypothesis that endogenous IFN-gamma contributes to the development of crescentic glomerulonephritis was tested by comparing the development of glomerulonephritis (induced by a planted antigen) and immune responses in normal C57BL/6 mice (IFN-gamma +/+) and in mice genetically deficient in IFN-gamma (IFN-gamma -/-). Ten days after the initiation of glomerulonephritis, IFN-gamma -/- mice developed fewer glomerular crescents (5+/-1% versus 26+/-3%, P<0.005), less severe glomerular injury, and less renal impairment. Effectors of delayed-type hypersensitivity (CD4+ T cells, macrophages, and fibrin) in glomeruli were reduced in IFN-gamma -/- mice. Skin delayed-type hypersensitivity to sheep globulin was reduced. Total antigen-specific Ig and splenocyte interleukin-2 production were unchanged, but antigen-specific serum IgG2a was reduced. Markers of an antigen-specific Th2 response (serum IgG1, splenocyte interleukin-4) were unchanged. Studies 22 d after the initiation of glomerulonephritis showed that IFN-gamma -/- mice still had fewer crescents (11+/-2% versus 22+/-3%, P = 0.02) and glomerular CD4+ T cells and macrophages than IFN-gamma +/+ mice. These studies demonstrate that endogenous IFN-gamma mediates crescentic glomerulonephritis by promoting cell-mediated immune injury. They support the hypothesis that crescentic glomerulonephritis is a manifestation of a Th1 nephritogenic immune response.     

Induction of interleukin 6 synthesis in mouse glomeruli and cultured mesangial cells.

Interleukin 6 (IL-6) is an autocrine growth factor of cultured mesangial cells (MC) and intraglomerular IL-6 production is suggested to be closely associated with the pathogenesis of human mesangial proliferative glomerulonephritis (mesPGN). In this study, to elucidate the mechanisms regulating the intraglomerular production of IL-6, we examined what kinds of stimuli are significant in the induction of IL-6 synthesis in vitro and in vivo. Incubation of cultured mesangial cells with interleukin 1 (IL-1) or bacterial lipopolysaccharide (LPS) induced significant IL-6 production, and intravenous injection of IL-1 or LPS into normal BALB/c mice induced significant intraglomerular IL-6 mRNA expression. Furthermore, we indicated in this study that IL-6 mRNA expression was augmented in the glomeruli of mice with immune complex-mediated glomerulonephritis.     

Retinoic acid treatment protects MRL/lpr lupus mice from the development of glomerular disease

BACKGROUND: Retinoic acid (tRA) is an active metabolite of vitamin A with potent anti-inflammatory properties. We analyzed the effects of tRA on the development of lupus nephritis in MRL/lpr mice. METHODS: MRL/lpr mice received chow supplemented with vehicle or tRA (daily 10 mg/kg) from 8 to 14 weeks until their sacrifice. MRL/wt mice served as an additional control. RESULTS: tRA-treated MRL/lpr mice showed reduced lymphoadenopathy and splenomegaly as compared to vehicle-treated controls. Treatment reduced proteinuria to almost basal levels. Plasma IgG and anti-DNA antibodies increased comparably in both vehicle and tRA-treated mice. Vehicle-treated mice showed characteristic renal lesions. In contrast tRA-treated mice showed almost normal glomerular histology with a pronounced reduction in endocapillary cell proliferation. T-cell and macrophage infiltrates were reduced after tRA treatment within glomeruli and interstitium as compared to vehicle-treated animals. In spite of this, immune complex and complement deposition were comparable in both groups. Adoptively transferred T cells from vehicle-treated to tRA-treated MRL/lpr mice did not induce renal lesions or proteinuria. These beneficial effects of tRA treatment were associated with reduced renal expression of chemokines and inflammatory cytokines. Surprisingly, renal transforming growth factor-beta (TGF-beta) mRNA levels of tRA-treated mice were elevated, possibly indicating that TGF-beta acts as an anti-inflammatory signal in this lupus model. CONCLUSION: tRA treatment reduces lymphoproliferation and glomerulonephritis in MRL/lpr mice. This occurs in spite of unaltered anti-DNA titers and glomerular immune complex deposition, and cannot be overcome by T-cell transfer from nephritic MRL/lpr mice.     

Chemokine receptor Ccr2 deficiency reduces renal disease and prolongs survival in MRL/lpr lupus-prone mice

MRL/MpJ-Fas(lpr)/J (MRL/lpr) mice represent a well-established mouse model of human systemic lupus erythematosus. MRL/lpr mice homozygous for the spontaneous lymphoproliferation mutation (lpr) are characterized by systemic autoimmunity, massive lymphadenopathy associated with proliferation of aberrant T cells, splenomegaly, hypergammaglobulinemia, arthritis, and fatal immune complex-mediated glomerulonephritis. It was reported previously that steady-state mRNA levels for the chemokine (C-C motif) receptor 2 (Ccr2) continuously increase in kidneys of MRL/lpr mice. For examining the role of Ccr2 for development and progression of immune complex-mediated glomerulonephritis, Ccr2-deficient mice were generated and backcrossed onto the MRL/lpr genetic background. Ccr2-deficient MRL/lpr mice developed less lymphadenopathy, had less proteinuria, had reduced lesion scores, and had less infiltration by T cells and macrophages in the glomerular and tubulointerstitial compartment. Ccr2-deficient MRL/lpr mice survived significantly longer than MRL/lpr wild-type mice despite similar levels of circulating immunoglobulins and comparable immune complex depositions in the glomeruli of both groups. Anti-dsDNA antibody levels, however, were reduced in the absence of Ccr2. The frequency of CD8+ T cells in peripheral blood was significantly lower in Ccr2-deficient MRL/lpr mice. Thus Ccr2 deficiency influenced not only monocyte/macrophage and T cell infiltration in the kidney but also the systemic T cell response in MRL/lpr mice. These data suggest an important role for Ccr2 both in the general development of autoimmunity and in the renal involvement of the lupus-like disease. These results identify Ccr2 as an additional possible target for the treatment of lupus nephritis.     

Toll样受体4信号对结肠癌细胞免疫抑制性细胞因子的调控

目的探讨Toll样受体（TLRs）对原位结肠癌细胞免疫抑制性细胞因子的调控作用及其机制。方法分别采用RT—PCR和蛋白印迹法对HT-29细胞中TLRs mRNA及蛋白质的表达进行检测。ELISA法检测经LPS刺激后及NF—κKB被抑制后,HT-29细胞所分泌的免疫抑制性细胞因子的改变。结果HT-29细胞可表达不同TLRs,以TLR4的表达为最高。经LPS刺激后,HT-29细胞中TLR4的mRNA和蛋白质水平,以及所分泌的转化生长因子（TGF）-β、VEGF、IL-8、CCL20和IL-6均显著升高（P〈0．01）。TGF—β、VEGF、IL-8和CCL20的上调表达不能被NF—κB抑制剂吡咯烷二硫代氨基甲酸盐（PDTC）所抑制,但IL-6的上调表达则依赖于NF—κB的活性。结论结肠癌细胞TLRs通过识别病原体相关模式分子．启动免疫抑制性细胞因子的表达．使肿瘤细胞逃避免疫监视。     

Glomerular expression of CD80 and CD86 is required for leukocyte accumulation and injury in crescentic glomerulonephritis

The participation of renal expression of CD80 and CD86 in the immunopathogenesis of crescentic Th1-mediated anti-glomerular basement membrane (anti-GBM) glomerulonephritis (GN) has not been assessed. Immunohistochemical staining demonstrated prominent upregulation of both molecules in glomeruli of mice with anti-GBM GN, suggesting a potential role for the local expression of CD80 and CD86 in nephritogenic effector T cell responses. For testing this hypothesis, control or inhibitory anti-CD80 and/or anti-CD86 mAb were administered to mice during the effector phase of the disease but after the establishment of a systemic immune response. Anti-CD80 or anti-CD86 mAb treatment had no effect on the development of GN or infiltration of leukocytes into glomeruli; however, administration of anti-CD80/86 mAb attenuated glomerular accumulation of CD4+ T cells and macrophages, crescent formation, and proteinuria, correlating with reduced antigen-specific skin delayed-type hypersensitivity. Attenuated glomerular infiltration of leukocytes in mice that were treated with anti-CD80/86 mAb was associated with decreased intraglomerular expression of adhesion molecules P-selectin and intercellular adhesion molecule-1, as well as attenuated renal mRNA levels of proinflammatory cytokines IFN-gamma and migration inhibitory factor, without reducing chemokine and chemokine receptor expression in the kidney or intraglomerular apoptosis and proliferation. The systemic Th1/Th2 balance (assessed by splenocyte production of IFN-gamma and IL-4 and circulating levels of IgG1 and IgG2a) was not affected by the inhibition of CD80 and CD86. These studies show that CD80 and CD86 are expressed in glomeruli of mice with crescentic anti-GBM GN, in which they play a critical role in facilitating accumulation of Th1 effectors and macrophages, thus exacerbating renal injury.     

Late onset of treatment with a chemokine receptor CCR1 antagonist prevents progression of lupus nephritis in MRL-Fas(lpr) mice

Slowly progressive renal injury is the major cause for ESRD. The model of progressive immune complex glomerulonephritis in autoimmune MRL(lpr/lpr) mice was used to evaluate whether chemokine receptor CCR1 blockade late in the disease course can affect progression to renal failure. Mice were treated with subcutaneous injections of either vehicle or BX471, a nonpeptide CCR1 antagonist, three times a day from week 20 to 24 of age [corrected]. BX471 improved blood urea nitrogen levels (BX471, 35.1 +/- 5.3; vehicle, 73.1 +/- 39.6 mg/dl; P < 0.05) and reduced the amount of ERHR-3 macrophages, CD3 lymphocytes, Ki-67 positive proliferating cells, and ssDNA positive apoptotic cells in the interstitium but not in glomeruli. Cell transfer studies with fluorescence-labeled T cells that were pretreated with either vehicle or BX471 showed that BX471 blocks macrophage and T cell recruitment to the renal interstitium of MRL(lpr/lpr) mice. This was associated with reduced renal expression of CC chemokines CCL2, CCL3, CCL4, and CCL5 and the chemokine receptors CCR1, CCR2, and CCR5. Furthermore, BX471 reduced the extent of interstitial fibrosis as evaluated by interstitial smooth muscle actin expression and collagen I deposits, as well as mRNA expression for collagen I and TGF-beta. BX471 did not affect serum DNA autoantibodies, proteinuria, or markers of glomerular injury in MRL(lpr/lpr) mice. This is the first evidence that, in advanced chronic renal injury, blockade of CCR1 can halt disease progression and improve renal function by selective inhibition of interstitial leukocyte recruitment and fibrosis.     

Mesangial immune complex glomerulonephritis due to complement factor D deficiency

Complement factor D is a serine protease essential for the activation of the alternative pathway and is expressed in the kidney, adipocytes, and macrophages. Factor D is found at relatively high levels in glomeruli suggesting that this component of the complement cascade could influence renal pathophysiology. In this study, we utilize mice with a targeted deletion of the activating complement factor D gene and compare these results to mice with targeted deletion of the inhibitory complement factor H gene. Eight-month-old mice with a deleted factor D gene spontaneously develop albuminuria and have reduced creatinine clearance due to mesangial immune complex glomerulonephritis. These mesangial deposits contain C3 and IgM. In contrast to the mesangial location of the immune deposits in the factor D-deficient mice, age-matched factor H-deficient mice develop immune deposits along the glomerular capillary wall. Our observations suggest that complement factor D or alternative pathway activation is needed to prevent spontaneous accumulation of C3 and IgM deposits within the mesangium. Our studies show that the complement factor D gene knockout mice are a novel model of spontaneous mesangial immune complex glomerulonephritis.     

Glomeruli synthesize nitrite in experimental nephrotoxic nephritis

Activated macrophages synthesize nitric oxide (NO) from L-arginine. In culture, the major stable end product is nitrite (NO2). Activated macrophages accumulate in glomeruli and are responsible for injury in experimental immune complex glomerulonephritis. We examined NO2- production by isolated glomeruli and urinary NO2- in accelerated nephrotoxic nephritis in the rat. Normal glomeruli did not produce NO2- spontaneously or when stimulated with lipopolysaccharide (LPS) (1 microgram/ml) or A23187 (2 microgram/ml). Cultured mesangial cells at first or seventh passage did not produce NO2- spontaneously or when stimulated. Nephritic glomeruli spontaneously produced NO2 at all times studied; this production was maximal at 24 hours after induction of glomerulonephritis (158.4 +/- 8.4 nmol/48 hr/ml, N = 3). The production of NO2- was inhibited 75 to 100% by NG-monomethyl-L-arginine (L-NMMA), and this inhibition was reversed by L-arginine, indicating NO2- production from L-arginine via NO. The production of NO2- was increased by LPS (1 microgram/ml) at 2, 7 and 21 days. NO2- was undetectable in normal rat urine; however, it was present in urine of rats with glomerulonephritis (Day 0 to 1:8161 +/- 2605 nmol/24 hr. N = 12). The production of NO in nephritic glomeruli may have implications for both the mechanism of glomerular injury and glomerular hemodynamics.     

CD28 superagonist-induced regulatory T cell expansion ameliorates mesangioproliferative glomerulonephritis in rats

Background

Naturally occurring regulatory T cells (Treg) are essential for the prevention of autoimmunity and overshooting immune responses to pathogens; however, the involvement of Treg in mesangioproliferative glomerulonephritis, a major cause of chronic kidney disease, remains unclear. Superagonistic CD28-specific monoclonal antibodies (CD28SA) are highly effective activators of Treg in rats.

Method

To confirm our hypothesis that CD28SA reduces the severity of experimental glomerulonephritis, anti-Thy1 nephritis model rats were treated with CD28SA or saline.

Results

CD28SA significantly suppressed the increase in proteinuria and serum creatinine levels. CD28SA-treated nephritic rats exhibited an increase in the infiltration of Treg in the glomeruli accompanied by infiltration of CD163-positive macrophages (??alternatively activated?? macrophages). In addition, CD28SA significantly induced interleukin-10 mRNA expression in glomeruli, thereby ameliorating mesangial cell proliferation and extracellular matrix expansion.

Conclusion

We established a new therapeutic approach to suppressing progressive glomerulonephritis. The therapeutic value of this approach warrants further attention and preclinical studies.     

Endogenous myeloperoxidase promotes neutrophil-mediated renal injury, but attenuates T cell immunity inducing crescentic glomerulonephritis

Myeloperoxidase (MPO) is an enzyme that is found in neutrophils and monocytes/macrophages. Intracellularly, it plays a major role in microbial killing, but extracellularly, it may cause host tissue damage. The role of endogenous MPO was studied during neutrophil-mediated (heterologous) and T helper 1 (Th1)/macrophage-mediated (autologous) phases of crescentic glomerulonephritis. Glomerulonephritis was induced in C57BL/6 wild-type (WT) and MPO-deficient (MPO(-/-)) mice by intravenous injection of sheep anti-mouse glomerular basement membrane globulin. MPO activity was increased in kidneys of WT mice during both the heterologous and autologous phases of glomerulonephritis. During the heterologous phase of glomerulonephritis, proteinuria was decreased, whereas glomerular neutrophil accumulation and P-selectin expression were enhanced in MPO(-/-) mice. In the autologous, crescentic phase of glomerulonephritis, MPO(-/-) mice had increased accumulation of CD4(+) cells and macrophages in glomeruli compared with WT mice. However, no difference in renal injury (crescent formation, proteinuria, and serum creatinine levels) was observed. Neutrophils and macrophages from MPO(-/-) mice exhibited reduced production of reactive oxygen species. Assessment of systemic immunity to sheep globulin showed that MPO(-/-) mice had increased splenic CD4(+) cell proliferation, cytokine production, and dermal delayed-type hypersensitivity, as well as enhanced levels of circulating IgG, IgG1, and IgG3. MPO(-/-) mice also had an augmented Th1:Th2 ratio compared with WT mice (IFN-gamma:IL-4 and IgG3:IgG1 ratios). These results suggest that endogenous MPO locally contributes to glomerular damage during neutrophil-mediated glomerulonephritis, whereas it attenuates initiation of the adaptive immune response inducing crescentic, autologous-phase glomerulonephritis by suppressing T cell proliferation, cytokine production, and Th1:Th2 ratio.     

Intrinsic renal cell expression of CD40 directs Th1 effectors inducing experimental crescentic glomerulonephritis

Evidence suggests that human and experimental crescentic GN results from Th1-predominant immunity to glomerular antigens. CD40/CD154 signaling plays a key role in initiating Th1 responses and may direct Th1 effector responses. The role of CD40 in the development of GN was assessed in murine experimental anti-glomerular basement membrane GN. In this model, C57BL/6 wild-type (WT) mice sensitized to sheep globulin develop crescentic GN resulting from Th1 effector responses when challenged with sheep globulin planted in glomeruli. CD40-/- mice do not develop immunity in response to sheep globulin and thus fail to develop effector responses or significant GN. CD40 is expressed in nephritic glomeruli, suggesting a potential role for intrarenal CD40-CD154 interactions in injurious effector responses. Immune neutralization of the CD40 ligand (CD154) at the time of challenge significantly reduced accumulation of Th1 effectors and injury. The role of CD40 expression by renal cells was assessed by comparing GN in WT-->CD40-/- chimeras (absent renal but intact bone marrow CD40) and sham chimeric mice (WT-->WT). Both groups developed strong antigen-specific immune responses (antibody and IFN-gamma production). However, WT-->CD40-/- chimeras demonstrated reduced renal monocyte chemotactic protein 1 and IFN-inducible protein 10 mRNA levels and minimal T cell and macrophage influx and were protected from renal injury. Sham chimeric mice developed reduced GFR, with prominent renal expression of monocyte chemotactic protein 1 and IFN-inducible protein 10 mRNA and effector cell accumulation. In conclusion, the expression of CD40 by nonimmune renal cells plays a major role in Th1 effector responses by inducing Th1 chemokine production. Therefore, CD40-CD154 interactions are a potential therapeutic target in GN.