Deficient IgA1 immune response to nasal cholera toxin subunit B in primary IgA nephropathy

Twelve IgA nephropathy (IgAN) patients and 18 controls were immunized with novel protein antigens, cholera toxin subunit B (CTB) via the nasal route and keyhole limpet hemocyanin (KLH) subcutaneously. Antibody secreting cells and antibody response in body fluids were determined by ELISPOT assay and ELISA, respectively. Analysis of variance showed, in contrast to controls (P < 0.001), no CTB-specific IgA response in the nasal washes of patients with IgAN. Significantly lower numbers of CTB-specific antibody-secreting cells in peripheral blood (P < 0.001) and CTB-specific antibodies in plasma (P < 0.005) were found in IgAN, both restricted to the IgA1 subclass. The proportions of CTB-specific IgA1-secreting cells in bone marrow aspirates correlated significantly with the corresponding ratios in plasma, with significantly lower values (P < 0.005) in IgAN as compared to controls. These results support the existence of a "mucosa-bone marrow axis" in humans, but no dysregulation of this axis was found in IgAN. The deficient mucosal IgA immune response to CTB observed in this study after primary mucosal immunization indicates that patients with IgAN have a defective immune response when challenged intranasally. These patients may depend on more frequent and/or prolonged antigen encounter at mucosal sites before efficient mucosal immunity is established. Repeated seeding of antigen-specific cells to secondary lympoid organs could result secondarily in the relative hyperresponsiveness found in IgAN upon reactivation by parenteral immunization.

Heterozygous and homozygous factor H deficiency states in a Dutch family

Factor H, a 150-kD protein, is an important down-regulating protein of the alternative pathway of the complement system. Presently, only 15 persons, representing seven families, have been described with homozygous factor H deficiency. Deficiency of this protein, inherited as an autosomal recessive trait and resulting in uncontrolled breakdown of C3, results in depletion of components of the alternative pathway (factor B, properdin) and of the terminal pathway (C5), and is associated with the onset of bacterial infections, glomerulonephritis and systemic lupus erythematosus (SLE). The proband of the family in this study suffered from subacute cutaneous lupus erythematosus and had had meningococcal meningitis due to serogroup X. She had a complete factor H deficiency at the protein level as determined by Western blotting. Among 21 relatives of the proband studied, encompassing three generations, 10 had low factor H levels, including the two children of the proband, indicating a heterozygous factor H deficiency state. In serum samples of the proband and 11 relatives prospectively studied, a strong correlation of factor H levels with C3, C3 haemolytic activity, factor B and properdin levels (P < 0.0001) was found. Alternative pathway protein levels were significantly lower (Mann-Whitney test; Z values 3.6-2.7) in sera from the four heterozygous relatives studied than in sera from the seven non-deficient relatives. In addition, a defect of the 37/42-kD H-related protein was found in the proband and two of 21 relatives, compared with four of 40 controls. A defect of the 24/29-kD H-related protein was present in one of 21 relatives studied and in none of the 40 controls.

Expression of the activation antigen CD27 in rheumatoid arthritis

Differentiation of CD4+ T-cells is reflected by the change from the CD45RA+CD27+ phenotype via CD45RO+CD27+ to the CD45RO+CD27- phenotype. To provide insight into the migration and activation of T-cells at the site of inflammation in rheumatoid arthritis (RA), CD27 expression by T-cells in peripheral blood (PB), synovial fluid (SF), and synovial tissue (ST) as well as the levels of the soluble form of CD27 (sCD27) in plasma and SF were studied in patients with RA. Since CD4+CD27+ T-cells are involved in providing helper activity for B-cells, we also investigated the levels of rheumatoid factors in serum and SF in relation to CD27 expression. The mean level of sCD27, which is produced by CD27+ cells, and the mean percentage of CD27 T-cells within the CD4+CD45RA- subset were higher in SF than in PB. SF sCD27 levels were higher in the patients with RA than in the patients with osteoarthritis, who served as controls. In ST infiltration by CD4+CD45RO+CD27+ T-cells, could be demonstrated in the rheumatoid perivascular lymphocytic aggregates with a relative increase in the percentage of CD27- T-cells in the diffuse lymphocytic infiltrate. The sCD27 levels and the percentages of CD4+CD27+ cells in SF correlated positively with the levels of rheumatoid factors in serum and SF. The findings presented in this study suggest a continuous influx of preactivated CD4+CD45RO+CD27+ cells from the PB into the rheumatoid ST and further activation and differentiation to CD4+CD45RO+CD27- cells in situ, followed by migration to the SF. These activated T-cells are likely to play a role in synovial inflammation.

Elastase, but not proteinase 3 (PR3), induces proteinuria associated with loss of glomerular basement membrane heparan sulphate after in vivo renal perfusion in rats

Elastase, but not PR3, induces proteinuria associated with loss of glomerular basement membrane (GBM) heparan sulphate after in vivo renal perfusion in rats. PR3 and elastase are cationic neutral serine proteinases present in the azurophilic granules of polymorphonuclear leucocytes. Release of these proteolytic enzymes along the glomerular capillary wall may induce glomerular injury. Here, we investigated the effects of PR3 and elastase on the induction of proteinuria and glomerular injury after renal perfusion of these enzymes in Brown-Norway rats. Perfusion of active elastase induced a dose-dependent proteinuria 24h after perfusion, while inactivated elastase did not. Perfusion of comparable amounts of active PR3 did not induce proteinuria. Light and electron microscopy showed no morphological abnormalities in any experimental group. However, immunohistology revealed that proteinuria occurring after perfusion of active elastase was associated with a strong reduction in intraglomerular expression of the heparan sulphate side chain and, to a lesser extent, of the protein core of heparan sulphate proteoglycans (HSPG). In vitro, both elastase and PR3 digested HSPG. However, PR3 bound to a lesser extent to HSPG than elastase. We conclude that elastase, but not PR3, induces proteinuria after in vivo renal perfusion. This differential effect probably relates to different binding to the GBM of those enzymes due to differences in their isoelectric points. Degradation of heparan sulfate proteoglycans, leading to the disappearance of their side chains that contribute to the polyanionic structure of the GBM, appears to be involved in the induction of proteinuria after perfusion of elastase.

CD32 expression and signaling is down-regulated by transforming growth factor-beta 1 on human monocytes

CD32 (Fc gamma RII) is the most abundantly distributed class of IgG Fc receptors in the human body. In this study, we analyzed the effect of transforming growth factor (TGF)-beta 1, a cytokine with strong immunosuppressive function, on the expression and function of CD32 on freshly isolated peripheral blood monocytes and three human monocytic cell lines, U937, THP-1 and Mono mac-6. We found that TGF-beta 1 down-regulates CD32 expression on monocytes and all monocytic cell lines in a dose- and time-dependent fashion. A mean down-regulation of CD32 expression on THP-1 cells of 54 +/- 3.2% after 24 h was found at a concentration of 1 ng/ml TGF-beta 1. At the mRNA level, TGF-beta 1 induced a twofold down-regulation of CD32. Cross-linking of CD32 induced an increase in the concentration of intracellular Ca2+, which was reduced by 50% by TGF-beta 1, suggesting a decreased downstream signaling mediated by the receptor.

Porcine islet cells of Langerhans are destroyed by human complement and not by antibody-dependent cell-mediated mechanisms

In the near future, xenotransplantation of porcine islets of Langerhans might be an alternative in the treatment of patients with diabetes mellitus. However, xenotransplantation of islets of Langerhans in large animals has been shown to result in an exceedingly short graft survival, which suggests that a humoral immune response might play a major role in islet demise. This study was performed to assess binding human preformed antibodies to isolated porcine islet cells (PIC) and to determine the lysis of PIC using human sera in complement-mediated cytotoxicity (CMC) and antibody-dependent cell-mediated cytotoxicity (ADCC) assays. Ten Dutch Landrace pigs were used for the isolation of PIC. Sera from 30 healthy blood donors (1/10 diluted) were used in a 51Cr release assay to assess CMC. Heat-inactivated normal human sera and fresh sera from patients with agammaglobulinemia were used as controls. Binding of human IgM IgG, and IgA antibodies to PIC was tested in an ELISA using isotype-specific secondary monoclonal antibodies ADCC was tested in a 51Cr release assay using normal human sera and sera from newly diagnosed type I diabetics with peripheral blood mononuclear cells as effector cells and PIC as targets. It was found that PIC were recognized by human IgM and IgG preformed antibodies and that fresh human sera had strong CMC activity inducing a percentage-specific PIC lysis of 61 +/- 10% (mean +/- SD) within 60 min. Agammaglobulinemic sera killed 42 +/- 12% of PIC. No significant cytotoxic activity was found in ADCC assays using normal sera or sera from diabetic patients. These results show that all tested human sera lyse PIC via CMC, even in the absence of human antibodies, as concluded from the use of agammaglobulinemic sera. In pig-to-human transplantation, islets may be hyperacutely rejected by antibody-dependent and antibody-independent activation of complement and not by antibody-dependent cell-mediated mechanisms.

Interleukin-1 alpha enhances the biosynthesis of complement C3 and factor B by human kidney proximal tubular epithelial cells in vitro

Local production in tubular cells of complement has been shown to occur in several kidney diseases by in situ hybridization, but the regulation at the local site during an inflammation is still unknown. In the present study, we demonstrate that human proximal tubular epithelial cells (PTEC) are able to produce complement components C3 and Factor B under non-stimulated conditions in vitro. The basal production of both was increased by 0.5 ng/ml interleukin-1 alpha (IL-1 alpha) for C3: from 95.5 +/- 4.0 ng/10(6) cells to 416.5 +/- 4.9 ng/10(6), and for Factor B: from 271 +/- 7.0 ng/10(6) cells to 457.5 +/- 7.0 ng/10(6) cells. In contrast cytokines such as TNF-alpha, IFN-gamma, IL-10 and IL-15 had no detectable effect. The upregulation by IL-1 alpha was dose- and time-dependent. The response to IL-1 alpha was shown to be mediated via the IL-1 receptor, as the addition of recombinant interleukin-1 receptor antagonist inhibited the IL-1 alpha induced complement production by more than 80%. IL-1 alpha enhanced mRNA expression of both C3 and Factor B as demonstrated by RT-PCR and dot-blot analysis. This indicated that IL-1 alpha upregulated the expression of the C3 and Factor B at the transcriptional level. We hypothesize that in vivo the production of C3 and Factor B at the local site during an inflammatory response in the kidney may be regulated by IL-1 alpha produced by inflammatory cells.

Differential effects of angiotensin II and transforming growth factor beta on the production of heparan sulfate proteoglycan by mesangial cells in vitro

This study approaches the question of whether angiotensin II (AngII) and transforming growth factor beta (TGF-beta) are important mediators for mesangial heparan sulfate proteoglycan (HSPG) production. This might explain the beneficial effects of angiotensin-converting enzyme inhibitors observed in several kidney diseases independent from their hemodynamic effects. Metabolic-labeling studies revealed that AngII induced a decrease of HSPG synthesis with decreases in N-sulfation of the glycosaminoglycan side chains. ELISA measurements with a heparan sulfate (HS)-specific monoclonal antibody confirmed that AngII decreased HS production. AngII increased TGF-beta production in a dose-dependent fashion. Specific mRNA for the large basement membrane HSPG (perlecan) decreased, whereas mRNA for TGF-beta increased after incubation with AngII. Blockade of the Subtype 1 Ang-II receptor (ATR1) reversed both the effects of AngII on HSPG and TGF-beta production. Coincubation of the mesangial cells with neutralizing antibodies against TGF-beta significantly reduced the production of HS as compared with control and AngII. These results indicate that the decrease in HS synthesis induced by AngII is not mediated by an increase in TGF-beta, but on the contrary, the increase in TGF-beta partially counteracts the inhibition of HS production by AngII. Considering the important role of HSPG in maintaining the glomerular charge barrier, cell proliferation, and matrix interaction, downregulation of the production of this molecule by increased local AngII concentrations could have important consequences, such as albuminuria and matrix expansion.

Transforming growth factor-beta (TGF-beta) expression and interaction with proteinase 3 (PR3) in anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis

TGF-beta is a multifunctional cytokine modulating the onset and course of autoimmune diseases as shown in experimental models. The aim of this study was to investigate TGF-beta expression in ANCA-associated vasculitis (AAV), and the possible interactions of this cytokine with lysosomal enzymes identified as ANCA autoantigens (e.g. PR3). This included TGF-beta effects on the translocation of the lysosomal enzymes to the cell surface of polymorphonuclear neutrophils (PMN), and the presumed activation of non-bioactive, latent TGF-beta by these enzymes. Patients with various types of systemic vasculitis (SV) were studied, including three different types of AAV (Wegener's granulomatosis (WG), Churg-Strauss syndrome (CSS) and microscopic polyangiitis (MPA)). Regardless of the type of assay applied, the TGF-beta 1 isoform was found to be over-expressed in SV, including AAV, and to correlate with disease activity as shown for WG. Mean TGF-beta 1 plasma levels in AAV patients ranged from 8.9 ng/ml (WG) to 13.3 ng/ml (CSS) (control 4.2 ng/ml; P < 0.01), while TGF-beta 2 levels were not elevated. Flow cytometry analysis showed TGF-beta 1 to be a potent translocation factor for PR3 comparable to other neutrophil-activating factors such as IL-8. PR3 membrane expression on primed PMN increased by up to 51% after incubation with TGF-beta 1. PR3 itself was revealed as a potent activator of latent TGF-beta, thus mediating bioeffects of this cytokine. These findings, together with other features of TGF-beta such as induction of angiogenesis and its strong chemotactic capacity, indicate that TGF-beta might serve as a proinflammatory factor in SV, especially in AAV.

Immunoglobulin D enhances the release of tumor necrosis factor-alpha, and interleukin-1 beta as well as interleukin-1 receptor antagonist from human mononuclear cells

Immunoglobulin D (IgD) is normally present in only low concentrations in serum. In the hyper-IgD and periodic fever syndrome (HIDS), however, serum levels exceed 140 mg/l. This syndrome is further characterized by recurrent inflammatory febrile attacks together with an acute phase response and appearance of cytokines in the circulation. The role of IgD in the pathogenesis of HIDS and its relation to the increased cytokine concentrations is unclear. Therefore, we tested whether IgD, IgG and alpha 1-acid glycoprotein (AGP) isolated from human serum influence the synthesis of interleukin-1 beta (IL-1 beta), tumour necrosis factor-alpha (TNF-alpha), and IL-1ra, as measured by specific radioimmunoassays, in human peripheral blood mononuclear cells (PBMC). Incubation of PBMC with IgD and AGP for 24 hr led to increased release of IL-1 beta, TNF-alpha, and IL-lra. The magnitude of stimulation of IgD exceeded that of AGP; the effect by IgD was dose-dependent and showed a 30-fold (TNF-alpha) to almost 150-fold (IL-1 beta) increase at the highest concentration (50 mg/l), while AGP (750 micrograms/ml) only increased the cytokine secretion fourfold (TNF-alpha) to almost 30-fold (IL-1 beta). The effect of IgD on IL-1ra was less dramatic but a fivefold increase was observed at 50 mg/l compared with a 2.5-fold increase with AGP. IgD potentiated the effect of lipopolysaccharide (LPS) on secretion of both IL-1 beta and TNF-alpha, although the effect was most apparent for TNF-alpha. Apart from inducing IL-1ra synthesis, IgG did not influence cytokine release in human PBMC. These data indicate that IgD is a potent inducer of TNF-alpha, IL-1 beta and IL-1ra and thus may contribute to the pathogenesis of HIDS.

Decrease in cellularity and expression of adhesion molecules by anti-tumor necrosis factor alpha monoclonal antibody treatment in patients with rheumatoid arthritis

OBJECTIVE

The effect of chimeric anti-tumor necrosis factor alpha (TNF alpha) monoclonal antibody (MAb) therapy on synovial inflammation was studied in order to address the hypothesis that anti-TNF alpha therapy leads to down-regulation of adhesion molecules and a decrease in inflammatory cell influx in synovial tissue (ST).

METHODS

The immunohistologic features of synovial biopsy specimens, both before and 4 weeks after anti-TNF alpha MAb (cA2) therapy, were studied in 14 patients with rheumatoid arthritis (RA). The patients either received a placebo (n = 2), or were given intravenous doses of cA2 at 10 mg/kg (n = 5) or 20 mg/kg (n = 7).

RESULTS

A significant (P < 0.03) reduction in the mean scores for T cells and for the adhesion molecules, vascular cell adhesion molecule 1 and E-selectin, was observed after therapy with 10 mg/kg or 20 mg/kg of cA2 in RA patients.

CONCLUSION

The reduced expression of adhesion molecules, and the decrease in cellularity of rheumatoid ST after cA2 administration support the hypothesis that the antiinflammatory effect of anti-TNF alpha therapy might be partly explained by down-regulation of cytokine-inducible vascular adhesion molecules in ST, with a consequent reduction of cell traffic into joints.

Persistent CD3-crosslinking down-regulates interleukin-2 responsiveness in interleukin-2-competent cloned T cells: the possible involvement of protein kinase C

To investigate the regulation of interleukin-2 (IL-2) responsiveness of T cells, a human CD4+ T-cell clone with constitutive expression of IL-2 receptors was stimulated with recombinant IL-2 (rIL-2) in the presence or absence of immobilized anti-CD3 monoclonal antibodies (alpha CD3imm MoAb). Incubation of T cells with alpha CD3imm MoAb decreased IL-2-induced proliferation which could not be ascribed to the modulation of IL-2 receptor expression nor to cell death. Phorbol-myristate-acetate (PMA), an activator of protein kinase C (PKC), also induced down-regulation of IL-2 responsiveness. The alpha CD3sol MoAb, inducing Ca(2+)-mobilization without activating PKC, did not inhibit IL-2 responsiveness whereas cyclosporine A (CsA), a drug that inhibits the Ca(2+)-dependent activation pathway, did not prevent the induction of IL-2 hyporesponsiveness induced by alpha CD3imm MoAb. It is concluded that modulation of IL-2 responsiveness of T cells via the T-cell receptor/CD3 complex (TCR/CD3) may be mediated by a PKC-activating signal.

Inhibition of the hemolytic activity of the first component of complement C1 by an Escherichia coli C1q binding protein

Molecular mimicry is a well established mechanism via which bacteria protect themselves from complement-mediated killing. We have previously demonstrated that a number of human cells express receptors for C1q (C1qR) and that the soluble form of this receptor inhibits activation of the classical pathway of complement. We now investigated whether Escherichia coli possesses a C1qR-like protein that protects these bacteria from complement-mediated injury. By FACS analysis it was shown that approximately 60% of the bacteria bound C1q directly in the absence of Abs. With ELISA we confirmed that the bacterial cell envelope was able to bind C1q in a dose-dependent fashion. We isolated a cell envelope associated C1q binding protein (C1qBP) by C1q affinity chromatography, then by anion exchange chromatography and gel filtration chromatography. On SDS-PAGE, the m.w. of C1qBP appeared to be 57 kDa and 51 kDa under reducing and nonreducing conditions, respectively. It was demonstrated that C1qBP specifically binds C1q and inhibits the hemolytic activity of C1q in both a dose- and time-dependent fashion. The binding of C1qBP to C1q is inhibited by C1q itself and also by the collagen-like stalks and the globular heads of C1q. In this respect, bacterial C1qBP is different from human C1qR because the binding of C1q to C1qR is only inhibited by the collagen-like stalks of C1q and not by the globular heads of C1q. C1qBP, when bound to C1q, prevents the assembly with C1r and C1s to form a functional C1 complex. The occurrence of C1qBP is not limited to certain E. coli strains, but is also found on Staphylococcus aureus, Citrobacter freundii, and Pseudomonas aeruginosa. Also, the binding of 125(I)-labeled C1q to these bacteria is specific because the binding of C1q to these bacteria is inhibitable with isolated soluble C1qBP. These findings provide evidence for the existence of a C1qR-like protein on bacteria that might protect them from complement-mediated damage.

Increased urinary excretion of monocyte chemoattractant protein-1 during acute renal allograft rejection

BACKGROUND

Acute rejection is characterized histologically by infiltration of the interstitium by mononuclear cells. Monocyte chemoattractant protein 1 (MCP-1) has recently been identified as a monocyte chemotactic factor. This study examined the possible role of MCP-1 in renal transplantation.

METHODS

The concentration of MCP-1 in urine and serum of 19 renal transplant patients was investigated using an inhibition radioimmunoassay. The patients were divided into a non-rejection (NRj) and a rejection (Rj) group. Normal healthy volunteers were included as controls. Immunoperoxidase staining for MCP-1 and CD14, as a marker for macrophages, was performed in renal biopsies of transplant patients with rejection and six biopsies from histologically normal kidneys, as controls. The size of urinary MCP-1 was determined by gel filtration chromatography and in a number of fractions assessed for monocyte chemotactic activity using a modified Boyden chamber assay.

RESULTS

Urinary excretion of MCP-1 in the Rj group ranged between 250 ng/mmol Cr and 3148 ng/mmol Cr with a median of 612 ng/mmol Cr. This is significantly higher than the results in the NRj group, ranging between 47 ng/mmol Cr and 288 ng/mmol Cr with a median of 229 ng/mmol Cr. In the normal control group, urinary MCP-1 levels ranged between 38 ng/mmol Cr and 74 ng/mmol Cr with a median of 50 ng/mmol Cr. The fractional excretion of MCP-1, calculated on the basis of MCP-1 and creatinine clearances, was found also to be significantly higher in the Rj group as compared to the NRj group. However, there was no significant difference in the serum levels of MCP-1 between the Rj, NRj, and normal control group. The intensity of MCP-1 staining in tubular epithelial cells and the degree of CD14+ cells in the interstitium was significantly higher in renal allograft biopsies than in the normal kidneys. In addition, MCP-1 isolated from urine of renal transplant patients with rejection was filtered with apparent molecular weight of 13 kDa and 11 kDa. Both sizes are chemotactically active for monocytes.

CONCLUSIONS

These data suggest that urinary excretion of MCP-1 can be used as a marker for the episodes of acute rejection. The increase of urinary excretion of MCP-1 most likely is the result of local production by tubular epithelia cells. MCP-1 produced locally may, at least in part, be responsible for the influx of macrophages into the interstitium during rejection.

Inhibition of the hemolytic activity of the first component of complement C1 by an Escherichia coli C1q binding protein

Molecular mimicry is a well established mechanism via which bacteria protect themselves from complement-mediated killing. We have previously demonstrated that a number of human cells express receptors for C1q (C1qR) and that the soluble form of this receptor inhibits activation of the classical pathway of complement. We now investigated whether Escherichia coli possesses a C1qR-like protein that protects these bacteria from complement-mediated injury. By FACS analysis it was shown that approximately 60% of the bacteria bound C1q directly in the absence of Abs. With ELISA we confirmed that the bacterial cell envelope was able to bind C1q in a dose-dependent fashion. We isolated a cell envelope associated C1q binding protein (C1qBP) by C1q affinity chromatography, then by anion exchange chromatography and gel filtration chromatography. On SDS-PAGE, the m.w. of C1qBP appeared to be 57 kDa and 51 kDa under reducing and nonreducing conditions, respectively. It was demonstrated that C1qBP specifically binds C1q and inhibits the hemolytic activity of C1q in both a dose- and time-dependent fashion. The binding of C1qBP to C1q is inhibited by C1q itself and also by the collagen-like stalks and the globular heads of C1q. In this respect, bacterial C1qBP is different from human C1qR because the binding of C1q to C1qR is only inhibited by the collagen-like stalks of C1q and not by the globular heads of C1q. C1qBP, when bound to C1q, prevents the assembly with C1r and C1s to form a functional C1 complex. The occurrence of C1qBP is not limited to certain E. coli strains, but is also found on Staphylococcus aureus, Citrobacter freundii, and Pseudomonas aeruginosa. Also, the binding of 125(I)-labeled C1q to these bacteria is specific because the binding of C1q to these bacteria is inhibitable with isolated soluble C1qBP. These findings provide evidence for the existence of a C1qR-like protein on bacteria that might protect them from complement-mediated damage.

Expression of CD46, CD55, and CD59 on renal tumor cell lines and their role in preventing complement-mediated tumor cell lysis

Nucleated cells are protected from complement-mediated injury by the expression of membrane-bound regulators of complement activation (mRCA) CD46, CD55, and CD59. Increased expression of these mRCA may be a mechanism by which tumor cells protect themselves from complement-mediated injury and prevent an inflammatory response. In the present study, we have investigated whether human renal tumor cell lines and cultured proximal tubular epithelial cells express CD46, CD55, and CD59 and whether these mRCA influence complement-mediated lysis of these cells. The expression of CD46, CD55, and CD59 was measured by flow cytometry. To determine the effect of mRCA on lysis, tumor cells were opsonized with complement activating anti-HLA class l mAb. Lysis was measured in the presence or absence of anti-CD46, anti-CD55 or anti-CD59 mAb and serum as a source of complement, using a 51Cr release assay. Flow cytometric analysis revealed that renal tumor cell lines and proximal tubular epithelial cells all express CD46, CD55, and CD59. Lysis of renal tumor cell lines in the presence of rabbit serum depended on the number of HLA class I molecules expressed by the tumor cells. Using human serum, complement-mediated lysis was decreased by at least one-third as compared with rabbit serum. The susceptibility of renal tumor cells for complement-mediated lysis could be increased up to the level observed with rabbit serum by inhibiting the function of CD59. Inhibition of the function of CD46 or CD55 with mAb directed against these mRCA had no substantial effect on lysis. We conclude from this work that renal tumor cells and proximal tubular epithelial cells express CD46, CD55, and CD59. Of these mRCA, CD59 is most efficient in preventing complement-mediated lysis of these cells. Expression of mRCA on tumor cells may influence the effectiveness of immunotherapy with tumor-associated mAb.

Interstitial rejection, vascular rejection, and diffuse thrombosis of renal allografts. Predisposing factors, histology, immunohistochemistry, and relation to outcome

Histological and immunohistochemical analyses were made of biopsy specimens from 50 consecutive patients who experienced putative graft rejection. The mean age of the patients was 44.5 years (range, 17-69 years) and 26 were men. There were 67 evaluable allograft specimens, which were grouped according to the histological diagnosis: group 1, acute tubulointerstitial rejection (n = 42); group 2, acute vascular rejection (n = 18); and group 3, diffuse thrombosis (n = 7). Over a follow-up period of 21-57 months, the mean number of rejection episodes was 1.7, 2.8, and 3.3 in groups 1, 2, and 3, respectively. Allograft loss occurred in 7 out of 30, 10 out of 16, and 4 out of 4 patients in groups 1, 2, and 3, respectively. The following histological parameters differed significantly (P < 0.05) among the groups: interstitial edema, congestion of peritubular capillaries, glomerular thrombosis, and glomerular ischemia (group 3 > group 2 > group 1). Interstitial bleeding was seen more often in group 2 and 3 tissues than in group 1 specimens (P < 0.01). Immunohistochemical analyses showed that vascular rejection was associated with WT14 staining for monocytes and macrophages around the tubuli and with interstitial deposition of complement factor 3. With regard to serology, positive anti-endothelial cell antibody-dependent cellular cytotoxicity was associated with vascular rejection and thrombosis of the graft in all patients tested, and with graft loss in 75%. Pre-existent positive anti-IgG immunofluorescence on peritubular capillaries in pretransplant biopsy specimens incubated with patient serum was found in only 3 of the 50 patients, but was associated with graft loss in 2 of the 3. Cytomegalovirus infection was associated with a higher percentage of graft loss. There were significant intergroup differences in panel reactive antibodies before transplantation (P < 0.001), with higher titers in groups 2 and 3. The findings in relation to interstitial rejection are compatible with cellular rejection, while the data on vascular rejection support a humorally mediated pathogenesis.

Proteinase 3, the major autoantigen of Wegener's granulomatosis, enhances IL-8 production by endothelial cells in vitro

Proteinase 3 is the major target antigen of antineutrophil cytoplasmic autoantibodies (ANCA) in Wegener's granulomatosis and is contained in the azurophilic granules of polymorphonuclear neutrophils, the dominant cell type in vascular lesions during the early stages of systemic vasculitis. This study questioned whether neutrophil lysosomal enzymes, once released at the site of inflammation, are able to potentiate the influx of additional neutrophils by enhancing the production of the chemotactic cytokine interleukin-8 (IL-8) by endothelial cells. Therefore, human umbilical vein endothelial cells in culture were incubated with varying concentrations of highly purified proteinase 3, human neutrophil elastase, and cathepsin G for different time periods. The supernatants were subsequently assessed for IL-8 antigen by using a sandwich ELISA. The presence of both proteinase 3 and elastase resulted in an increased production of IL-8, up to 15.6- and 4.2-fold, respectively, in a dose- and time-dependent fashion. Cathepsin G did not influence IL-8 production. Although the addition of an alpha 1-proteinase inhibitor completely abrogated elastase-mediated IL-8 production, it did not significantly influence the effect of proteinase 3. Both proteinase 3-and elastase-mediated production of IL-8 was inhibited by cycloheximide, indicating de novo synthesis. This was supported by the finding of increased IL-8 mRNA levels in proteinase 3-treated human umbilical vein endothelial cells by using Northern blot analysis. Taken together, the neutrophil lysosomal enzymes proteinase 3 and human neutrophil elastase may contribute to a self-perpetuating process of neutrophil recruitment in acute inflammation by increasing de novo synthesis of IL-8 by endothelial cells. The studies presented here also show that proteinase 3 mediates its effect independently of its enzymatic activity, indicating a hitherto unknown mode of action on endothelial cells.

Search for the antigen-specificity of homogeneous IgG components (H-IgG) after allogeneic bone marrow transplantation

After allogeneic BMT, transient homogeneous Ig components (H-Ig) can be detected in the sera of most graft recipients. So far, data on the antigen-specificity and therefore the function of these H-Ig are not available. Such information may be important for our understanding of the underlying mechanisms that are responsible for these excessive clonal B cell expansions, and it may help to delineate the functional antibody repertoire after BMT. In the present study, sera of 98 paediatric BM graft recipients were investigated for the potential presence of H-Ig of IgG isotype (H-IgG) with specificity towards a panel of antigens, including vaccine and herpes virus antigens, auto-antigens and allo-antigens. The vast majority of H-IgG in sera of BM graft recipients were unreactive when tested for this panel of antigens. However, in four cases, antigen-specificity of H-IgG to tetanus toxoid could be demonstrated after vaccination with that antigen. An explanation for the negative findings may be either that a restricted antibody production had been elicited by other non-tested antigens, eg substances of colonizing and translocating bacteria or of food antigens, or that the H-IgG components may have anti-idiotype or anti-'self' specificity.

The tetracycline derivative minocycline differentially affects cytokine production by monocytes and T lymphocytes

Minocycline is a tetracycline derivative that has beneficial effects in noninfectious forms of arthritis and dermatitis. To investigate whether this effect may be attributed to interference with cytokine production, we studied the effect of minocycline on cytokine production by T cells and monocytes. Minocycline exerted an inhibitory effect on tumor necrosis factor alpha (TNF-alpha) and gamma interferon production by stimulated T cells, whereas the production of interleukin 6 (IL-6) remained unaffected. The effect of minocycline on TNF-alpha mRNA synthesis by T cells was shown to be stimulus specific. T cells stimulated by a Ca2+-independent mode exhibited a decrease in TNF-alpha mRNA in the presence of minocycline, whereas the TNF-alpha mRNA level remained unaffected by minocycline when cells were stimulated in a Ca2+-dependent manner. In contrast to the effect on T cells, addition of minocycline to lipopolysaccharide-stimulated monocytes led to a dose-dependent increase in TNF-alpha and IL-6 production which was paralleled by an enhancement of TNF-alpha mRNA synthesis. These results indicate that minocycline exerts differential effects on the regulation of cytokine production by T cells and monocytes that are partly reflected at the mRNA level. Given the pleiotropic effects of minocycline, it is suggested that the immunostimulatory effect on monocytes might counteract its beneficial properties in the treatment of several forms of chronic inflammation.

Effects of high glucose on the production of heparan sulfate proteoglycan by mesangial and epithelial cells

Changes in heparan sulfate metabolism may be important in the pathogenesis of diabetic nephropathy. Recent studies performed on renal biopsies from patients with diabetic nephropathy revealed a decrease in heparan sulfate glycosaminoglycan staining in the glomerular basement membrane without changes in staining for heparan sulfate proteoglycan-core protein. To understand this phenomenon at the cellular level, we investigated the effect of high glucose conditions on the synthesis of heparan sulfate proteoglycan by glomerular cells in vitro. Human adult mesangial and glomerular visceral epithelial cells were cultured under normal (5 mM) and high glucose (25 mM) conditions. Immunofluorescence performed on cells cultured in 25 mM glucose confirmed and extended the in vivo histological observations. Using metabolic labeling we observed an altered proteoglycan production under high glucose conditions, with predominantly a decrease in heparan sulfate compared to dermatan sulfate or chondroitin sulfate proteoglycan. N-sulfation analysis of heparan sulfate proteoglycan produced under high glucose conditions revealed less di- and tetrasaccharides compared to larger oligosaccharides, indicating an altered sulfation pattern. Furthermore, with quantification of glomerular basement membrane heparan sulfate by ELISA, a significant decrease was observed when mesangial and visceral epithelial cells were cultured in high glucose conditions. We conclude that high glucose concentration induces a significant alteration of heparan sulfate production by mesangial cells and visceral epithelial cells. Changes in sulfation and changes in absolute quantities are both observed and may explain the earlier in vivo observations. These changes may be of importance for the altered integrity of the glomerular charge-dependent filtration barrier and growth-factor matrix interactions in diabetic nephropathy.

1,25-dihydroxycholecalciferol enhances the expression of MHC class II antigens and intercellular adhesion molecule-1 by human renal tubular epithelial cells

PURPOSE

Beside its role in calcium and phosphorus metabolism, 1,25-dihydroxycholecalciferol (1,25-D3) exerts multiple effects on cytokine and major histocompatibility complex (MHC) class II expression in monocytes and lymphocytes. In different renal diseases tubular epithelial cells express MHC class II molecules and cell adhesion molecules,, such as intracellular adhesion molecule-1 (ICAM-1). Therefore, modulation of MHC class II and ICAM-1 expression in renal tubular epithelial cells by 1,25-D3 may be relevant to lymphocyte adhesion to tubular epithelial cells and immune mediated renal injury. However, the expression of MHC class II antigens and cellular adhesion molecules by renal tubular epithelial cells in response to 1,25-D3 has not been investigated.

MATERIALS AND METHODS

We generated human renal tubular epithelial cells and SV40 transfected tubular epithelial cells to investigate immune modulation of 1,25 on renal epithelial cells. Major histocompatibility complex class II molecules and ICAM-1 were detected by a specific enzyme linked immunoassay.

RESULTS

We found a dose-dependent increase of both constitutive and induced MHC class II and ICAM-1 expression in tubular epithelial cells stimulated with 1,25-D3. Dose-dependent stimulation of MHC class II and ICAM-1 expression was not restricted to primary human renal tubular epithelial cells but was also detected in SV40 transfected cells.

CONCLUSIONS

Expression of MHC class II and ICAM-1 is crucial for antigen presentation by and lymphocyte adhesion to renal tubular epithelial cells. Modulatory effects of 1,25-D3 on immune accessory function of renal tubular epithelial cells may be of clinical significance in renal diseases.

Both IgG- and C1q-receptors play a role in the enhanced binding of IgG complexes to human mesangial cells

The presence of immunoglobulin G (IgG) in the mesangial area in kidneys of patients with different forms of glomerulonephritis suggests a role for IgG in the inflammatory process. This study investigates whether IgG is able to bind to cultured human mesangial cells (MC) in vitro. Incubation of MC with 125I-aggregated IgG(125I-AIgG), as a model for immune complexes (IC), at 4 degrees C resulted in a time- and dose-dependent binding of 125I-AIgG to MC. The binding of 125I-AIgG to MC was inhibited by excess AIgG or Fc-fragments and not by F(ab')2-fragments or human serum albumin (HSA). Scatchard analysis revealed the presence of 2.8.10(6) receptors/cell with an affinity of 9.7.10(7) M-1. Incubation of MC with 125I-C1q resulted in a time- and dose-dependent binding of 125I-C1q to MC. The binding of 125I-C1q was inhibited by excess C1q or C1q talls and not by HSA. Scatchard analysis revealed the presence of 3.2.10(7) binding sites/cell with an affinity of 1.4.10(7) M-1. Immunoprecipitation of 125I-labeled MC membrane proteins with C1q or monoclonal antibodies directed against human C1q-R revealed a single 66 to 68 kd band under reducing conditions. Fluorescence-activated cell-sorter analysis revealed an average of 60.1% +/- 5.4% of the cells positive with a mean channel of fluorescence of 592. A cooperative effect between C1q-R and Fc gamma-R in the binding of 125I-AIgG to MC, was assessed by incubation of 125I-AIgG in the presence of increasing concentrations of C1q, C1q talls, or delta C1q. Only intact C1q showed a 6- to 11-fold enhancement in binding of 125I-AIgG to MC. These studies demonstrate the occurrence of C1q-R and Fc gamma-R on MC and indicate that binding of IC is enhanced after interaction of IC with C1q.

Differential expression of complement components in human fetal and adult kidneys

Various studies have shown that complement components are synthesized by renal cells and that mRNA for a number of complement components is detectable in renal tissue. The present study shows that complement proteins are present both in fetal and adult human kidneys. The localization of the complement components was compared with the localization of other proteins for which specific expression in defined renal cell types is known from the literature. In adult human kidneys C3, factor B and factor H were detected in the mesangial area by immunohistochemistry, whereas C2 and C4 were present in the proximal tubuli. In fetal kidneys C3 and factor B were expressed in glomeruli of kidneys of 11 weeks of gestation. In kidneys of 13 to 19 weeks of gestation no staining for C3 was found in the glomerulus, whereas for factor B glomerular staining was found in all fetal kidneys examined. Factor B was also detected in fetal tubuli and in the interstitium. Factor H was expressed in fetal tubuli starting at 13 weeks of gestation. For both C3 and C2 weak tubular staining was found in all fetal kidneys investigated. C4 could not be detected in any of the fetal kidneys. While not all the complement proteins investigated were detectable by immunohistochemistry, by RT-PCR analysis, mRNA expression for C3, factor B, factor H, C2 and C4 was found in all adult and fetal renal tissue. The finding of mRNA for the complement components in the fetal and the adult kidneys indicates that local synthesis of complement occurs both in the adult and in the fetal kidney. Next to the in situ expression of complement components in fetal kidneys the synthesis of complement proteins in vitro by fetal renal cells was investigated. Four different primary mesangial cell lines were shown to synthesize all complement proteins investigated. Although a specific role for complement during the development of the kidney is not known, it is possible that certain complement components may play a role during renal differentiation.