Diminished synthesis of immunoglobulin by peripheral lymphocytes of patients with idiopathic membranous glomerulonephropathy

Immunoglobulin G has a role for systemic protein modulation in vivo: a new concept of protein homeostasis

The constant level of various proteins including albumin and cellular components in intravascular pool in vivo is strictly controlled by an unknown homeostatic mechanism, although there are fluctuations seen in pathologic conditions. Because the majority of the IgG in the serum is regarded as self-reactive natural autoantibodies, IgG may have a role to react with all proteins in vivo. It is hypothesized that like an immune system, a homeostatic mechanism for the protein pool also has a sensitive role to identify and memorize the extent and repertoire of both normal and pathogenic proteins on an individual basis, and IgG may be one of the major players in performing these functions. This hypothesis may explain the unresolved clinical observations as followed: (1) the marked increased IgG levels observed in self-limiting diseases presumed to come from immunological insults such as acute poststreptococcal glomerulonephritis and Kikuchi-Fujimoto disease, (2) an immediate reduction of all protein levels except immunoglobulins after intravenous immunoglobulin (IVIG) treatment in Kawasaki disease, (3) a unified explanation for the variety of immunomodulating effects exerted by IVIG, (4) the IgG-enzyme complexes observed in benign conditions such as macroamylasemia and hyperphosphatasemia, and (5) the marked decreased IgG level, which is correlated with the albumin level in minimal change nephrotic syndrome. IgG may be a 'watch-dog' for the disturbances of protein homeostasis in vivo. IgG may control the pathogenic proteins that appeared in disordered states, and it may help prevent the loss of proteins in case of nephrotic syndrome.

Th2 cytokines increase and stimulate B cells to produce IgG4 in idiopathic membranous nephropathy

BACKGROUND

The predominant deposition of IgG4 in idiopathic membranous nephropathy indicates that its presence characterizes the systemic immune response of the disease.

METHODS

We analyzed the expressions of CD3, CD19, CD4, and CD8 on peripheral blood mononuclear cells (PBMCs) by flow cytometry, and the levels of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), interferon (IFN)-gamma, interleukin (IL)-4, IL-10, and IL-13 mRNAs in PBMCs using real-time reverse transcription-polymerase chain reaction (RT-PCR) in 14 patients with idiopathic membranous nephropathy and 14 normal control donors. The levels of IgG subclasses in the B-cell culture supernatant in the presence or absence of cytokines were quantified by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Idiopathic membranous nephropathy patients showed an increased CD4(+)/CD8(+) ratio, although the numbers of peripheral T and B cells were comparable to those of the normal control group. IL-10 and IL-13 mRNA expression levels increased in the idiopathic membranous nephropathy group. The levels of spontaneous production of each IgG subclass by B cells were identical in the two groups. In the presence of Th2 cytokines, B cells from several individuals of the idiopathic membranous nephropathy group augmented the production of IgG4. When the individual levels of each IgG subclass in the presence of cytokines were compared with those in the absence of cytokines in each sample, a significant increase in the production of IgG4 in the presence of IL-4 was observed in the idiopathic membranous nephropathy group.

CONCLUSION

These results indicate that the altered functions of T cells to produce Th2 cytokines and the increased production of IgG4 by B cells in response to these cytokines characterize the immune response in idiopathic membranous nephropathy.

Dietary protein intake does not affect IgG synthesis in patients with nephrotic syndrome

BACKGROUND

Low plasma IgG levels have long been reported as an important complication of the nephrotic syndrome. Few studies in vivo have evaluated IgG synthesis in nephrotic patients and no data are available on the effect of dietary protein restriction on the rate of IgG synthesis.

METHODS

We compared the IgG synthesis rates of seven nephrotic patients who assumed, for 4 weeks, either a normal protein diet (NPD) (1.20+/-0.06 g/kg/day) or a low-protein diet (LPD) (0.66+/-0.04 g/kg/day) with those of seven normal subjects (matched for age and body mass index). The post-absorptive fractional synthesis rate (FSR) and absolute synthesis rate (ASR) of IgG were evaluated during the last 120 min of a 5 h 5,5,5-D3-l-leucine infusion.

RESULTS

Compared with controls, in nephrotic patients the plasma IgG levels and pool were significantly reduced (P<0.05), while IgG FSR and ASR were increased by 4- and 2.5-fold, respectively (P<0.05). The LPD regimen did not affect plasma IgG FSR, ASR, circulating concentrations and intravascular pool (P = NS). There was a significant negative correlation between plasma IgG FSR and the IgG intravascular pool in nephrotic patients evaluated during both the NPD (r = -0.828; P<0.05) and LPD (r = -0.861; P<0.05) regimens.

CONCLUSIONS

Nephrotic syndrome patients with low plasma IgG levels have increased IgG FSR and ASR which are not affected by reduced dietary protein intake.

Short-term responsiveness of membranous glomerulopathy to cyclosporine

We administered a 12-week course of cyclosporine (CsA) (4 to 6 mg/kg/24 h) to nephrotic patients with membranous glomerulopathy (MG). Nephrotic patients with minimal change nephropathy (MCN) served as a comparison group. We evaluated the effects of CsA on proteinuria, glomerular function, and the release of cytokines by peripheral blood mononuclear cells in culture. Proteinuria was restored to normal levels within 2 to 4 weeks in MCN. Proteinuria declined from nephrotic to subnephrotic levels (< 3,500 mg/24 h) in 10 of 14 patients with MG, also within 2 to 4 weeks of onset of therapy. The four nonresponders exhibited a rapidly progressive and presumably irreversible form of MG culminating in renal failure. On average, fractional clearances of albumin and IgG declined by 59% and 73% in MG (P < 0.005); corresponding declines in MCN were by 99% (P < .0001). Corresponding rates of glomerular filtration in each glomerular injury remained unchanged. A strong trend for proteinuria to relapse after CsA was withdrawn was evident in both disorders. The release of tumor necrosis factor (TNF)-alpha by mononuclear cells in culture was enhanced in each glomerular injury, both before and after the course of CsA. We conclude that the proteinuria in most cases of MG exhibits a responsiveness to CsA that is qualitatively similar to, but less complete than, that in MCN. The rapidity with which barrier function improves suggests a possible role for cell-mediated immune injury in MG.

Decrease in serum antiphospholipid antibody levels upon development of nephrotic syndrome in patients with systemic lupus erythematosus: relationship to urinary loss of IgG and other factors

PURPOSE

Having observed a decrease in antiphospholipid antibodies (aPL) upon the development of nephrotic syndrome, as well as a negative association between nephrotic syndrome and secondary antiphospholipid syndrome, in patients with systemic lupus erythematosus (SLE), we sought to determine if this could be due to urinary loss of aPL and/or other factors.

SUBJECTS AND METHODS

IgG and IgM aPL as well as other autoantibodies were studied by enzyme-linked immunosorbent assay with cardiolipin as antigen in serum and urine from six patients with SLE who had elevated serum aPL levels and developed nephrotic syndrome (cases). For controls, we studied: (1) three SLE patients with nephrotic syndrome but low aPL levels; (2) three patients with non-SLE nephrotic syndrome; (3) three SLE patients with high-titer aPL but no proteinuria; and (4) 10 healthy volunteers.

RESULTS

We found urinary IgG, but no IgM, aPL in all cases and in one control from Group 2. Serum IgG aPL had gradually decreased after the development of nephrotic syndrome and had become normal. IgM aPL had also decreased in the four patients who had elevated levels, having reached normal levels at the time of the study in two. There was an apparent correlation between serum and urine IgG aPL levels but not between urinary IgG aPL and total proteinuria. By Farr's method, we found no urinary anti-DNA despite high serum titers in three cases. The two cases and one of the controls in Group 1 who had serum antibodies to extractable antigens also had these antibodies in the urine.

CONCLUSION

Urinary loss of IgG aPL during nephrotic syndrome does not completely explain the reduction in serum aPL, since IgM also decreases. There could also be decreased synthesis and/or increased catabolism of immunoglobulins.

Immunoregulation in Heymann nephritis. II. Functional studies

In this study, the functional properties of the cells involved in the immunoregulation of Heymann nephritis (HN) have been investigated. HN is a disease model in the rat where the pathology closely resembles membranous glomerulonephropathy (MGN) in man. This autoimmune model is induced by injection of renal tubular antigen (RTA) incorporated in Freund's complete adjuvant (FCA). The strong B cell and plasma cell response in the chronic phase of HN, as determined by cell marker analyses, is predominantly antigen-non-specific. The secondary response pattern found was not only to RTA upon repeated immunization, but also to non-related antigen (SRBC). Although cell marker studies have indicated no major quantitative changes in the T cell population throughout the development of HN, a severe deregulation of the cellular immune response is observed especially during the induction period of HN. This was shown by a strong decrease of the mitogen-induced proliferative response and IL-2 production. This phenomenon is caused by both defective cellular components and inhibitory serological factors. Finally, in the chronic phase, these aberrations gradually return to normal.

Immune mechanisms in idiopathic membranous nephropathy: the role of the interstitial infiltrates

Mononuclear inflammatory cells in renal biopsies from 36 patients with membranous nephropathy (MN) were analyzed, using monoclonal antibodies. In the interstitium, monocytes/macrophages and T cells were the predominant cell types (210 +/- 27 and 171 +/- 25/mm2, respectively); in contrast, very few intraglomerular leucocytes, mostly macrophages (1.0 +/- 0.7 cell/glomerular cross-section), were found. Among the interstitial T-cell population, helper/inducer cells (CD4+) predominated (CD4:CD8 ratio, 2.2 +/- 1.5). Natural killer (NK) cells and B lymphocytes were a minor component of the interstitial infiltrates and were almost absent in the glomeruli. Significantly higher numbers of DR-expressing cells were found in the interstitium (322 +/- 20/mm2) than in controls (109 +/- 30), but tubular DR expression was similar to controls (17 +/- 12 mm2). The numbers of total leukocytes and their subsets CD4+, CD8+, monocytes/macrophages, and B cells all correlated with the degree of renal impairment at the time of biopsy, but surprisingly there was no correlation between interstitial cell numbers and the histological severity of tubulointerstitial lesions. Progressive renal impairment over 5 years was associated with many interstitial T cells and monocytes/macrophages in the initial biopsy. Our results suggest that interstitial mononuclear cells may be important determinants in the pathogenesis of MN. Both cellular and humoral immune mechanisms may play a major role in the initiation of the disease, whereas progression toward renal failure seems to be determined mainly by cell-mediated immunity.

Hypogammaglobulinaemia in nephrotic rats is attributable to hypercatabolism of IgG

The effect of the nephrotic syndrome induced by puromycin aminonucleoside (PA) in rats on specific antibody responses to 2,4 dinitrophenyl (DNP) conjugated to either spider crab haemocyanin (MSH), a T cell-dependent antigen, or hydroxyethyl starch (HES), a T cell-independent type 2 antigen were studied. The serum IgG anti-DNP levels following immunization with both antigens were reduced in nephrotic animals compared with controls while IgM anti-DNP antibody titres were higher. The half-life of IgG anti-DNP antibodies passively transferred into non-immunized nephrotic rats was markedly reduced while the half-life of anti-DNP antibodies of the IgM class was comparable to that in controls. Low serum IgG and elevated IgM levels were seen in nephrotic animals compared to controls. Antibody-forming cells specific for DNP were demonstrated by immunohistology on rat spleens and the numbers of both IgG and IgM-producing cells were found to be significantly increased (P less than 0.05) in nephrotic animals in response to both DNP-HES and DNP-MSH. These data indicate that in nephrotic rats the alteration seen in the serum immunoglobulin levels is not attributable to reduced antibody production but increased catabolism of serum IgG antibodies.

Immune stimulation. A new approach in the treatment of glomerulonephritis

We discuss here a new approach to the treatment of idiopathic membranous glomerulonephritis (IMGN). Steroids and cytotoxic drugs have been used during the last years for the treatment of this disease, but the results are controversial. We develop here the hypothesis that the pathogenesis of IMGN is a relative incompetence of the immune system in clearing foreign antigens. Therefore, most patients should benefit from immune stimulation in the direction of a greater and more avid immune response.

Glomerular and serum immunoglobulin G subclasses in membranous nephropathy and anti-glomerular basement membrane nephritis

The distribution of human IgG subclasses among the glomerular deposits of 53 patients with glomerulonephritis was examined by immunofluorescence (IF) with subclass-specific monoclonal antibodies (Mab). A subclass restriction was observed in idiopathic membranous nephropathy (MN) with glomerular deposits predominantly containing IgG4 (81% of the studied biopsies) and IgG1 (75%). In de novo MN, occurring after transplantation, the restriction was markedly different, with a predominance of IgG1 (100%) and IgG2 (69%). In anti-glomerular basement membrane (a-GBM) nephritis the restriction was considerable with deposits containing almost exclusively IgG1 (91%) and IgG4 (73%). The same restriction was observed for circulating anti-GBM antibodies detected by indirect IF assay. By contrast IgG1, IgG2, and IgG3 deposits were identified in lupus proliferative glomerulonephritis. Serum IgG subclass levels were measured in 29 patients with idiopathic MN and a-GBM nephritis by an indirect competitive immunoenzymatic assay using Mab. Mean percentage of IgG2 serum level was significantly lower in patients. In spite of high variations from patient to patient, a serum IgG subclass imbalance was clearly present in 10 cases with low IgG2 and high IgG1 and IgG3 levels. The imbalance in these patients was not due to urinary loss since it was observed with a similar frequency in hypo- and normoimmunoglobulinemic patients. In 5 out of these 10 patients IgG2 levels were very low, analogous to those observed in selective IgG2 deficiency. Whether the important subclass restriction of glomerular IgG (in which patterns differed according to the type of glomerulonephritis) and the serum subclass imbalances were due to a clonally restricted antibody response to a particular antigen or to a host immune response defect, or both, remains to be elucidated.

Experimental strategies for the study of cellular immunity in renal disease

This overview has examined some of the current experimental options available for the study of cellular immunity in the immunopathogenesis of renal disease. T cell immunity, where it has been examined, seems to have a particularly pivotal role in orchestrating and regulating functional patterns of renal injury. The use of the research methods presented here for the study of cell-mediated interactional events in kidney disease, however, has lagged behind similar efforts in other organ systems. We hope, therefore, this report will serve to stimulate and strengthen further interest in the cell biology of the nephritogenic immune response.

Evidence for an endothelial cell-derived factor which stimulates the growth of human peripheral blood mononuclear cells

Evidence is provided which demonstrates that conditioned media of cultured endothelial cells derived from human umbilical veins contained a factor which stimulated peripheral blood mononuclear cell [3H]thymidine uptake. A dose-dependent response in peripheral blood mononuclear cell [3H]thymidine uptake was obtained when cells were incubated with increasing concentrations of supernatant of endothelial cell cultures. Studies on temporal kinetics demonstrated that stimulatory activity was evident when mononuclear cells had been incubated with endothelial cell supernatant for 120 hr or more. Preliminary characterization showed the growth immunoregulatory factor to have a molecular weight greater than 100,000 Da.

Strong association of HLA-DR2 and MT1 with idiopathic membranous nephropathy in Japan

Fifty adult Japanese patients with biopsy-proven idiopathic membranous nephropathy (IMN) were typed for HLA-A, B, and DR antigens, and additional B cell alloantigens designated the MT system. The phenotype frequencies of HLA-DR2 (80.0 vs. 36.0%) and MT1 (96.0 vs. 49.5%) appeared to be significantly increased in the patient group when compared to those of a control. There were lower frequencies of DR4, DRw9, MT3, and MT4 in these particular patients. The decreases of MT3 and MT4 were statistically significant but those of DR4 and DRw9 were not. These results suggest that HLA-DR2 and MT1 antigens are related to the occurrence of IMN in the Japanese population.

T cell subset modulation of immunoglobulin production in IgA nephropathy and membranous glomerulonephritis

Monoclonal antibodies directed against T cell subset antigens have been used to deplete peripheral blood human mononuclear cells from helper (OKT4+) and suppressor/cytotoxic (OKT8+) cells. Unfractionated cells and depleted cells were assayed for their capacity to modulate pokeweed mitogen (PWM)-driven IgG, IgA, and IgM production by autologous B lymphocytes. Immunoglobulin production in the presence of these various cell preparations paralleled the OKT4+/OKT8+ ratio defining the population. Importantly, there was no clear relationship between the level of PWM-driven Ig production by unfractionated cells and their initial relative content in OKT4+ and OKT8+ cells. Patients with IgA nephropathy and membranous glomerulonephritis showed a statistically significant increase of OKT4+/OKT8+ ratio, suggestive of suppressor T cell deficiency. There was no increase in IgA production in patients with IgA nephropathy, even in those showing high serum IgA level. A special feature found in patients with IgA nephropathy, irrespective of OKT4+/OKT8+ ratio in unfractionated cells, was a particularly intense enhancement of IgA production after OKT8+ cell depletion in some of the patients, contrasting with a particularly low effect of such depletion on the synthesis of all Ig classes in other patients. In patients with membranous glomerulonephritis there was no obvious abnormality in the modulation of Ig production by T cell subsets, with the exception of a weak suppressor activity with respect only to IgM production in a significant number of patients.

Immunoregulation in glomerulonephritis, Henoch--Schonlein purpura and lupus nephritis

Immunoregulation was examined in normal controls and in patients with immune complex glomerulonephritis and lupus nephritis (SLE) using OKT monoclonal anti-bodies against helper (OKT4) and suppressor (OKT8) T cell subsets. Functional studies assessed T cell control of in vitro immunoglobulin synthesis by cultured peripheral blood mononuclear cells (PBMC). IgG and IgA synthesis was measured in unstimulated, pokeweed mitogen (PWM) stimulated and PWM + concanavalin A (Con A) stimulated cultures. Patients with primary membranous nephropathy (MN) and mesangial IgA nephropathy (IgA GN) were found to have elevated T4/T8 ratios secondary to a deficiency of the T8+ subset. Patients with SLE had low T4/T8 ratios. B cell activation with high spontaneous immunoglobulin synthesis was present in cell cultures from patients with SLE, IgA GN and Henoch-Schonlein purpura (HSP). Defective Con A inducible suppression of in vitro immunoglobulin synthesis was found in SLE, HSP and to a lesser extent, primary MN. Functional Con A inducible suppressor defects correlated with elevated T4/T8 ratios only in patients with MN. All four disorders appear to share disturbances of cellular immune response with various degrees of defective immune suppression; however, it is not clear from these studies whether the defects are primary or secondary phenomena.

Identification of a monocyte phagocytic defect in a subpopulation of patients with nephritis

Experimental studies have demonstrated the cardinal role played by the mononuclear phagocyte system in the removal of antigen-antibody complexes. To assess the functional capacity of phagocytes in patients with renal disease, 33 normal subjects, 10 patients with mesangial proliferative glomerulonephritis, 8 patients with membranous nephropathy, and 8 patients with moderately severe chronic renal failure were studied by an in vitro assay, measuring the ability of isolated monocytes to ingest sheep erythrocytes coated with IgG antibody and to phagocytize latex beads. Monocytes from four patients with mesangial proliferative glomerulonephritis and one patient with membranous nephropathy exhibited a subnormal capacity to ingest the antibody-coated erythrocytes. Additionally, monocytes from two of the four patients with mesangial proliferative glomerulonephritis and a defect in ingesting sensitized erythrocytes had a subnormal capacity to phagocytize latex beads. The results are interpreted in the context of a hypothesis which suggests that patients with immune nephritis show various forms of immune deficit.

T cell subset alterations in idiopathic glomerulonephritis

Peripheral blood lymphocytes from 15 healthy controls and 59 patients with idiopathic glomerulonephritis were studied to determine whether an imbalance exists among human T cell subsets in these diseases. Twenty of the patients studied had a minimal change nephropathy (10 with nephrotic syndrome and 10 in sustained remission); 27 had a membranous glomerulonephritis (12 with nephrotic syndrome, six with isolated proteinuria and nine in complete remission); 12 patients had an IgA glomerulonephritis with heamaturia and mild proteinuria. Monoclonal antibodies directed at human T lymphocyte subsets termed OKT3, OKT4 and OKT8 were used in an indirect immunofluorescence assay in all cases. Patients with minimal change nephropathy, with or without nephrotic syndrome and patients with IgA glomerulonephritis showed mean values of OKT3⁺ cells (total peripheral T cells), helper OKT4⁺ cells, suppressor OKT8⁺ cells and OKT4⁺/OKT8⁺ cell ratio, in the normal range. Only the group of patients with membranous glomerulonephritis and nephrotic syndrome presented a mean OKT4⁺/OKT8⁺ ratio greater than the normal group (percentages: 2·43±0·3 vs 1·6±0·1 s.e.m.; P<0·02). This increased ratio was due to a reduction in the OKT8⁺ cell subset compared to the healthy subjects (percentages: 27·6±2·9 vs 36·8±1·4 s.e.m.; P<0·01). Our data shows that the functional lymphocyte disorders previously described in minimal change nephropathy and IgA glomerulonephritis are not due to a numerical imbalance of lymphocyte subsets. Such an imbalance of lymphocyte subsets was specifically observed in membranous glomerulonephritis with nephrotic syndrome. The true significance of this finding has to be clarified by longitudinal studies and functional tests.

Angioimmunoblastic lymphadenopathy with hypogammaglobulinemia. Possible role of monocyte suppression

A patient wit angioimmunoblastic lymphadenopathy had low serum immunoglobulin values and no antibodies to injected immunogens. This occurred despite the proliferation of polyclonal B cells. T cells were deficient in number and in lymphoproliferative responses, but their helper and suppressor functions were maintained. Ia-antigen bearing leukocytes from the patient stimulated poorly in mixed leukocyte culture. In vitro immunoglobulin synthesis by mononuclear leukocytes form the patient was severely impaired. These leukocytes actively suppressed immunoglobulin synthesis by normal cells from healthy subjects in co-culture. The responsible cell had characteristics of a monocyte. The suppression was selective for humoral immunity and was manifest despite normal numbers of monocytes. It appears that heterogeneous immunoregulatory abnormalities can underlie the syndrome of angioimmunoblastic lymphadenopathy. Furthermore, monocyte suppressor abnormalities may be implicated in clinical disease phenomena.

Abnormalities of T-cell subsets in glomerulonephritis and systemic lupus erythematosus

In this study, three kinds of monoclonal antibodies directed at human T lymphocytes, produced by mouse hybridomas and termed OKT3, OKT4, and OKT8, were used in an indirect immunofluorescence assay, to analyze the distribution of peripheral T lymphocyte subsets in 41 patients with glomerulonephritis (GN) and 11 patients with systemic lupus erythematosus (SLE). As assessed by functional studies, OKT4 and OKT8 defined the helper and cytotoxic/suppressor T lymphocytes subsets, respectively, whereas OKT3 recognized all peripheral T-cells. Among GN patients, the ones presenting membranous GN (MGN), IgA disease, and lipoid nephrosis associated with segmental and focal hyalinosis (FGS) showed significant decrease of their peripheral cytotoxic/suppressive T cells. On the contrary, no significant alteration was found in the peripheral T cell distribution of patients with membranoproliferative GN (MPGN) and lipoid nephrosis associated with minimal-change GN (MCGN). Unexpectedly, there was a tendency for peripheral cytotoxic/suppressive T lymphocytes to be high in the majority of SLE patients, and only two of these subjects exhibited a relative decrease in peripheral OKT8 marked cells. The steroid therapy received by our patients might account for this discrepancy with previous reports of altered suppressor function in active SLE.