Hiroyuki Ohi

Complement activation through the lectin pathway in patients with Henoch-Schönlein purpura nephritis

Henoch-Schönlein purpura nephritis (HSPN) is considered a form of systemic vasculitis of the small blood vessels with immune pathogenesis. In this disorder, the complement system is recognized as an important mechanism of glomerular injury. The aim of this study is to determine whether the lectin pathway, a novel pathway of complement activation, is related to the pathogenesis of HSPN. Renal biopsy material from 10 patients with HSPN was studied immunohistochemically and examined for a clinicopathologic correlation. Serum levels of complement components, including mannose-binding lectin (MBL), and plasma levels of complement activation products were also evaluated in these patients and compared with levels in patients with immunoglobulin A (IgA) nephropathy or mesangial proliferative glomerulonephritis (GN) without IgA deposition (non-IgA GN). Glomerular deposition of components of the pathway, MBL and MBL-associated serine protease (MASP-1), as well as C3b/C3c, C5b-9, and C4-binding protein (C4-bp), was detected in 8 of 10 patients. Although no significant correlation was found between glomerular deposition of MBL/MASP-1 and histological or clinical findings, the biopsies on all patients with MBL/MASP-1 deposits were performed within 20 weeks from the onset of disease. Levels of plasma C4d, the activation fragment of C4, and C4-bp, a soluble regulatory protein of the pathway, were greater in patients with HSPN than in those with non-IgA GN. However, there was no difference in serum MBL levels between the three groups of patients (HSPN, IgA nephropathy, and non-IgA GN). These results suggest that complement activation through the lectin pathway was involved at the onset of HSPN, and this mechanism might be important in the disease pathogenesis.

Murine fetal resorption and experimental pre-eclampsia are induced by both excessive Th1 and Th2 activation

It has been proposed that immune responses in mammalian normal pregnancy are Th2-like, thereby protecting the fetus and placenta from being rejected. Administration of exogenous Th1 cytokines into pregnant mice is reported to induce feto-placental resorption. However, the effects of exogenous Th2 cytokines and Th2 directed responses in pregnant animals have not been well studied. In this study, we examined IL-4 and IL-12, which play decisive roles in the development of Th2 and Th1 responses, respectively, in the induction of fetal resorption and development of experimental pre-eclampsia. Transfer of either IL-4 and/or IL-12 stimulated splenocytes from BALB/C virgin female mice into BALB/C pregnant mice mated with either C57BL/6 or BALB/C male mice resulted in fetal resorption and glomerular nephritis associated with hypertension and proteinuria. In mice treated with IL-12 stimulated splenocytes, fatty liver degeneration associated with bile retention was observed. These results indicate that both excessive Th1 and Th2 activation contribute to the development of fetal resorption and pre-eclampsia, but that Th1 is critical to the development of liver degeneration.

Two types of C3 nephritic factor : properdin-dependent C3NeF and properdin-independent C3NeF

The IgG fraction of serum from patients with membranoproliferative glomerulonephritis (MPGN) types I and II or partial lipodystrophy (PLD) was found to contain C3 nephritic factor (C3NeF) which reacts with the alternative pathway C3 convertase C3bBb and stabilizes it. Two types of C3NeF were detected, of which one was heat sensitive (56 degrees C for 30 min) and properdin dependent (C3NeF:P) but the other was heat stable and properdin independent (C3NeF:nP). C3NeF:P was found in sera from patients with MPGN types I and II and it displayed the properties of properdin and IgG. C3NeF:P was observed in patients with reduced serum concentrations of C3 and terminal complement components (TCC), and the generation of SC5b-9 complex was increased in mixtures with normal human serum. C3NeF:nP was found in sera from patients with MPGN type II and PLD, whose sera revealed a selective decrease in C3 concentrations.

Interleukin 10 and interleukin 13 synergize to inhibit vascular permeability factor release by peripheral blood mononuclear cells from patients with lipoid nephrosis

It has been proposed that a vascular permeability factor (VPF) is involved in the pathogenesis of lipoid nephrosis (LN). There is now increasing evidence that interleukin 10 (IL-10) and interleukin 13 (IL-13) have regulatory effects on cytokine production by activated macrophages. These results prompted us to study the effects of recombinant human IL-10 and IL-13 on VPF secretion in LN. In the present study, we demonstrate that the regulatory cytokines IL-10 and IL-13 are potent inhibitors of the VPF activity of activated peripheral blood mononuclear cells. Each cytokine was found to suppress VPF secretion in a dose-dependent fashion. More importantly, the combination of the cytokines was found to give a potent synergistic suppression of VPF by concanavalin A activated peripheral blood mononuclear cells from patients with LN. When both anti-IL-10 and anti-IL-13 antibodies were added together to the peripheral blood mononuclear cells, a further increase of concanavalin A enhanced secretion of VPF occurred. These data establish IL-10 and IL-13 as potent inhibitors of VPF activity and suggest their utility in controlling deleterious VPF-mediated responses such as occur in LN patients with nephrotic syndrome.

Significance of glomerular activation of the alternative pathway and lectin pathway in lupus nephritis

The objective of the present study was to elucidate the association between glomerular complement depositions belonging to the alternative (AP) and lectin (LP) pathways, and clinical findings of lupus nephritis (LN). Immunofluorescence (IF) was performed on 17 LN patients using antibodies against factor B, factor H, properdin, mannose-binding lectin (MBL) and L-ficolin. Compared with factor B/factor H negative patients (n = 9), positive patients (n = 8) showed longer duration of LN (p < 0.05) and more severe interstitial fibrosis (p < 0.05). Eleven patients had properdin deposition in glomeruli, and in three of them, with a duration of LN of less than 1 month, factor B was undetectable. Compared with properdin negative patients (n = 6), positive patients (n = 11) showed significantly higher urinary protein excretion (p < 0.01). MBL/L-ficolin positive patients (n = 11) also had significantly higher urinary protein excretion (p < 0.05) compared with negative patients (n = 6). An independent association was found between glomerular deposition of properdin and that of MBL/L-ficolin (p < 0.01) in addition to factor B/factor H. Traces of glomerular activation of AP and LP reflected the clinical status of LN. It appears that glomerular deposition of each complement component, especially properdin, may be an index of the histological activity of LN.

Excretion of complement proteins and its activation marker C5b-9 in IgA nephropathy in relation to renal function.

BackgroundGlomerular damage in IgA nephropathy (IgAN) is mediated by complement activation via the alternative and lectin pathways. Therefore, we focused on molecules stabilizing and regulating the alternative pathway C3 convertase in urine which might be associated with IgAN pathogenesis.MethodsMembrane attack complex (MAC), properdin (P), factor H (fH) and Complement receptor type 1 (CR1) were quantified in urine samples from 71 patients with IgAN and 72 healthy controls. Glomerular deposition of C5, fH and P was assessed using an immunofluorescence technique and correlated with histological severity of IgAN and clinical parameters. Fibrotic changes and glomerular sclerosis were evaluated in renal biopsy specimens.ResultsImmunofluorescence studies revealed glomerular depositions of C5, fH and P in patients with IgAN. Urinary MAC, fH and P levels in IgAN patients were significantly higher than those in healthy controls (p < 0.001), but CR1 was significantly lower than that in healthy controls (p < 0.001). Urinary MAC and fH levels were positively correlated with serum creatinine (sCr), urinary N-acetyl-β-D-glucosaminidase (u-NAG), urinary β2 microglobulin (u-Bm), urinary protein (p < 0.001), interstitial fibrosis (MAC: p < 0.01, fH: p < 0.05) and the percentage of global glomerular sclerosis (p < 0.01). Urinary P was positively correlated with u-NAG, u-Bm, and urinary protein (p < 0.01).ConclusionsComplement activation occurs in the urinary space in IgAN and the measurement of levels of MAC and fH in the urine could be a useful indicator of renal injury in patients with IgAN.

Significance of C3 nephritic factor (C3NeF) in non-hypocomplementaemic serum with membranoproliferative glomerulonephritis (MPGN)

C3NeF is an autoantibody of C3 convertase (C3bBb) and is often detected in the serum of hypocomplementaemic MPGN patients. Serum samples from 104 non‐hypocomplementaemic MPGN patients (C3NeF) were studied. C3NeF, which cannot activate the alternative pathway, was found in the sera of 6 patients. We examined the C3NeF in purified IgG from five of the non‐hypocomplementaemic serum samples (non‐hypo C3NeF) and four hypocomplementaemic serum samples (hypocomplementaemic C3NeF) to determine why C3NeF does not induce C3 splitting and hypocomplementaemia. Purified IgG from non‐hypo C3NeF stabilized EAC4b3bBb cells in a manner similar to IgG from hypocomplementaemic C3NeF in EDTA gelatin veronal buffer. However, the non‐hypo C3NeF IgG did not stabilize C3 convertase (EAC4b3bBb cells) in the presence of control proteins (factors H and I), whereas the hypocomplementaemic C3NeF IgG did. The C3NeF in the hypocomplementaemic serum displayed two characteristics: (i) inhibition of intrinsic decay of Ce convertase (C3bBb); and (ii) inhibition of extrinsic decay by factors H and I. Although the C3NeF in the non‐hypocomplementaemic sera did inhibit the intrinsic decay in a manner similar to the hypocomplementaemic C3NeF IgG, it did not inhibit the extrinsic decay. Due to the different characteristics of hypocomplementaemic C3NeF and non‐hypo C3NeF in the serum samples, the non‐hypo C3NeF did not activate C3. Therefore, we conclude that C3NeF exhibits a heterogeneity which is very important in relation to the pathogenesis of MPGN.

Complement Activation Accelerates Glomerular Injury in Diabetic Rats

A known inhibitor of the complement cascade (K-76 COONa) was administered to an inbred diabetic rat model to investigate whether the complement system may play a role in the progression of diabetic glomerulosclerosis. Drinking water containing K-76 COONa was available continuously to inbred diabetic rats (Otsuka Long-Evans Tokushima Fatty, OLETF) from the age of 25 to 55 weeks (Group L). Drinking water without K-76 COONa was similarly available to OLETF rats (Group H) and nondiabetic control rats (Long-Evans Tokushima Otsuka, LETO) (Group C). The levels of plasma glucose (mg/dl) at the 55th week were 156 ± 16 in Group C, 252 ± 18 in Group L and 349 ± 93 in Group H. There was no significant difference in the degree of diabetes between Group L and Group H. The levels of urinary protein at 55 weeks of age (mg/day) were 2.1 ± 0.4 in Group C, 11.6 ± 1.5 in Group L and 18.0 ± 2.8 in Group H. The level of urinary protein was significantly decreased by the administration of K-76 COONa. Histological examination of renal specimens from the sacrificed rats at 55 weeks of age revealed diffuse mesangial expansion in almost all glomeruli in Group H, exudative lesions in 30% of glomeruli in Group H, and only mild mesangial expansion was recognized in Group L. Immunofluorescence study revealed brilliant staining of C3 and immunoglobulins (Ig) in Group H; trace staining of Ig and no staining of C3 were recognized in Group L. The incubation study with guinea pig serum and glomeruli from rats revealed that Ig and complement components also bound to injured glomeruli in vitro. These data indicate that the complement cascade is activated by injured glomeruli and this activation exacerbates diabetic glomerulosclerosis.

Interleukin-4 Cooperates with Interleukin-10 to Inhibit Vascular Permeability Factor Release by Peripheral Blood Mononuclear Cells from Patients with Minimal-Change Nephrotic Syndrome

Increased production of a vascular permeability factor (VPF) from peripheral blood mononuclear cells (PBMC) in patients with minimal-change nephrotic syndrome (MCNS) has been reported. Interleukin-4 (IL-4) and interleukin-10 (IL-10), both produced by T-helper type-2 cells, are cytokines with the capacity to downregulate proinflammatory responses. To gain insight into the immunoregulatory properties of these cytokines, we analyzed the effects of recombinant human IL-4 and IL-10 on VPF release in MCNS patients. In the present study we show that the regulatory cytokines IL-4 and IL-10 are potent inhibitors of the VPF activity of concanavalin A-activated MCNS PBMC. Each cytokine was found to suppress VPF release in a dose-dependent manner. Moreover, when used at suboptimal concentrations, a combination of the two cytokines resulted in enhanced suppression of VPF release. Neutralization of endogenously produced IL-4 and IL-10 by both anti-IL-4 and anti-IL-10 antibodies resulted in an increased release of VPF. These data demonstrate that IL-4 acts in concert with IL-10 to inhibit VPF release and suggest that they are effective biologic regulators of the VPF responses in vitro.

Significant Elevations in Serum Mannose-Binding Lectin Levels in Patients with Chronic Renal Failure

Background/Aims: Mannose-binding lectin (MBL), a liver-derived C-type serum lectin, activates the complement cascade through the lectin pathway. Since the complement system contributes to the host defense against infections and mediates inflammatory processes including atherosclerosis, and since chronic renal failure (CRF) patients are prone to the development of infectious complications and cardiovascular disease, we focused on serum MBL levels in CRF patients who were either uremic, or who were receiving hemodialysis treatment. Methods: MBL levels were measured in the sera of subjects with CRF before they began dialysis treatment (pre-HD patients; n = 23) and in the sera of subjects who were receiving maintenance hemodialysis (HD patients; n = 178), by ELISA using polyclonal anti-rabbit IgG and a monoclonal antibody directed against MBL (3E7). Results: Mean levels (± SD) of serum MBL were significantly higher in pre-HD subjects (4.343 ± 2.533 µg/ml, p < 0.05) and in HD subjects (8.897 ± 4.920 µg/ml, p < 0.05), than in healthy controls (1.452 ± 0.692 µg/ml). Levels were also significantly higher in HD subjects than in pre-HD subjects (p < 0.05). Conclusions: Elevated serum MBL levels in patients with CRF might have significantly influence pathologic conditions such as alterations of the immune system and acceleration of atherogenesis.