Detection of circulating immune complexes in patients with glomerulonephritis

The Potential of Harnessing IL-2-Mediated Immunosuppression to Prevent Pathogenic B Cell Responses

Immunosuppressive drugs can partially control Antibody (Ab)-dependent pathology. However, these therapeutic regimens must be maintained for the patient's lifetime, which is often associated with severe side effects. As research advances, our understanding of the cellular and molecular mechanisms underlying the development and maintenance of auto-reactive B cell responses has significantly advanced. As a result, novel immunotherapies aimed to restore immune tolerance and prevent disease progression in autoimmune patients are underway. In this regard, encouraging results from clinical and preclinical studies demonstrate that subcutaneous administration of low-doses of recombinant Interleukin-2 (r-IL2) has potent immunosuppressive effects in patients with autoimmune pathologies. Although the exact mechanism by which IL-2 induces immunosuppression remains unclear, the clinical benefits of the current IL-2-based immunotherapies are attributed to its effect on bolstering T regulatory (Treg) cells, which are known to suppress overactive immune responses. In addition to Tregs, however, rIL-2 also directly prevent the T follicular helper cells (Tfh), T helper 17 cells (Th17), and Double Negative (DN) T cell responses, which play critical roles in the development of autoimmune disorders and have the ability to help pathogenic B cells. Here we discuss the broader effects of rIL-2 immunotherapy and the potential of combining rIL-2 with other cytokine-based therapies to more efficiently target Tfh cells, Th17, and DN T cells and subsequently inhibit auto-antibody (ab) production in autoimmune patients.

Dysregulation of T Follicular Helper Cells in Lupus

Although multiple and overlapping mechanisms are ultimately responsible for the immunopathology observed in patients with systemic lupus erythematosus, autoreactive Abs secreted by autoreactive plasma cells (PCs) are considered to play a critical role in disease progression and immunopathology. Given that PCs derive from the germinal centers (GC), long-term dysregulated GC reactions are often associated with the development of spontaneous autoantibody responses and immunopathology in systemic lupus erythematosus patients. In this review, we summarize the emerging evidence concerning the roles of T follicular helper cells in regulating pathogenic GC and autoreactive PC responses in lupus.

High titer anti-basement membrane antibodies in a subset of patients with pediatric systemic lupus erythematosus

BACKGROUND/AIMS

There is a critical need for more noninvasive biomarkers to identify nephritis in patients with systemic lupus erythematosus (SLE). Recent studies in a model mouse and an adult SLE patient cohort suggest that anti-basement membrane antibody levels correlate well with lupus activity and kidney injury. The purpose of this study was to assess the anti-basement membrane reactivity in pediatric SLE (pSLE) patients with or without nephritis.

METHODS

Auto-antibodies to basement membrane antigens were assessed using an anti-matrigel ELISA. Endpoint titers were measured in pSLE patients and healthy children, as well as in autoimmune and non-immune mice, with good reproducing capabilities. Findings were also analyzed with respect to the presence or absence of nephritis, dsDNA antibodies, and other manifestations of pSLE.

RESULTS

MRL/lpr mice developed high-titer anti-matrigel antibodies, whereas C57BL/6 mice did not. In a cohort of 21 pSLE patients and 22 pediatric controls, high-titer anti-matrigel IgG, IgM and IgA antibody levels were specific for pSLE. High-titer anti-matrigel IgG3 levels could distinguish with good sensitivity the 13 pSLE patients with a history of nephritis from the 8 non-renal pSLE patients. High-titer anti-matrigel IgG, IgA, IgM or IgG3 did not correlate with positive anti-double stranded DNA, but defined an overlapping subset of patients.

CONCLUSION

The addition of anti-basement membrane antibody testing to serologic testing in pSLE may help to monitor disease activity or to define important subsets of patients with risks for specific disease manifestations.

Accelerated decay of the cell bound C4b2a complex by serum of patients with membranoproliferative glomerulonephritis and acute poststreptococcal glomerulonephritis

Serum from patients with membranoproliferative glomerulonephritis (MPGN) and acute poststreptococcal glomerulonephritis (APSGN) accelerated the decay of the cell bound C4b2a (C42) and C4b hemolytic activity relative to pooled normal human serum (pNHS) after 5 min incubation at 30 degrees C in EDTA-GVB. The accelerated decay of the C42 hemolytic activity was heat stable (56 degrees C 30 min) and was inhibited by monoclonal antibody against human C4 binding protein (MoAb:C4BP) or C4 binding protein (C4BP) depleted serum. C4 nephritic factor (C4NeF) was employed to stabilize the labile classical pathway C3 convertase C42 complex. Serum from patients with MPGN and APSGN reduced the C4NeF stabilizing activity. Sera from 32 of 46 patients with MPGN and all of 7 patients with APSGN reduced the C42 hemolytic activity relative to 50 normal human serum (NHS) after 5 min incubation at 30 degrees C in EDTA-GVB, and there was no relationship with the serum concentration of C4BP. In vivo, accelerated decay of C42 convertase might interfere with the clearing and processing mechanism of circulating immune complexes (IC) by reducing deposition of C3b on the IC lattice.

Autoreactive mechanisms in infective endocarditis

Infective endocarditis is not a simple interaction between a microbial agent and a cardiac valve. For the infection of a non-bacterial thrombotic vegetation, predisposition is required which is at least partially operative by a decreased suppressor T cell activity. During infection, peripheral blood natural killer cell activity is decreased, but normalizes under anti-microbial therapy. Non-major histocompatibility complex-restricted lymphocytotoxicity to isolated heart cells can be present in one third of patients. Circulating immune complexes normalize during therapy. They may be the cause of many clinical symptoms of infective endocarditis. Anti-bacterial and also anti-sarcolemmal antibodies which are cross-reactive to the bacterium are secreted in a polyclonal immune response. Anti-sarcolemmal antibodies which are cytolytic in vitro in the presence of complement may partly explain the myocardial factor of heart failure in patients with only marginal valve incompetence due to the endocarditic vegetation.

Antibody to a cryptic, solid phase C1Q antigen in membranoproliferative nephritis

IgG containing material detected in membranoproliferative nephritis (MPGN) serum with a solid phase (sp) Clq ELISA has been presumed to be immune complexes. However, in serum from 13 MPGN patients containing large amounts of spClq-binding material, sucrose density ultracentrifugation and sieve chromatography showed spClq-binding protein to sediment at 7S or cofractionate with IgG. One serum (stored for 12 years) contained, in addition, spClq-binding material sedimenting at more than 19S. Isolated MPGN IgG was shown to bind to spClq. SpClq-binding material could be totally removed from MPGN serum by absorption with BSA-anti-BSA immune precipitates, and by acid elution of the precipitates IgG binding to spClq could be recovered. F(ab')2, isolated from pepsin digested MPGN IgG, continued to bind spClq. Binding of MPGN IgG or F(ab')2 to spClq was not inhibited by 2 M NaCl. Incubation of MPGN serum with 125I Clq followed by sucrose density ultracentrifugation resulted in a peak of radioactivity at 11S, the sedimentation rate of Clq, giving evidence that material binding fluid phase Clq is not present. SpClq-binding IgG was detected in 54% of 68 MPGN patients. These results indicate that the 7S spClq-binding IgG represents antibody to a cryptic antigen revealed only when Clq fixes to a solid surface.

Detection of bovine serum albumin in the circulating IgA immune complexes of patients with IgA nephropathy

Alimentary antigenic challenge has been postulated to have a role in the genesis of IgA circulating immune complexes (CIC), resulting in mesangial IgA disease. In this study, we examined the relationship between bovine serum albumin (BSA) and IgA CIC in patients with IgA nephropathy. Of the 47 patients studied, elevated IgA CIC levels were found in 32% by the F(ab')2 anti-C3 and Raji cell enzyme immunoassays (EIA). Elevated IgA anti-BSA antibody levels were found in 9 patients, and there was a positive correlation between these levels and IgA CIC as measured in the Raji cell EIA (R = 0.60, P less than 0.001). In 4 patients with elevation of both IgA CIC and IgA anti-BSA antibody levels, solubilization experiments were done to demonstrate the presence of BSA antigen in the IgA CIC. Using the Raji cell EIA, the IgA CIC levels decreased significantly after preincubating the sera with serial concentrations of excess BSA. No corresponding effect was seen with human serum albumin used as control. Hence, BSA may be the antigenic stimulus in the formation of IgA CIC in selected patients with IgA nephropathy. The pathogenic capacity of these IgA-BSA CIC remains to be determined.

Role of immune complexes in pathogenesis of renal disease

When judged by histological criteria, kidney tissue is practically devoid of immune tissue; as yet a broad spectrum of immunological diseases are targeted at the kidneys, especially at the glomeruli. Glomerular epithelial cells exhibit immune protein receptors and hence could clear immune complexes decorated with complement from the circulation. Alternatively, circulating immune complexes could become trapped in the glomerular filter and start off inflammatory reactions. Anti-glomerular basement membrane antibody reacts with glomeruli and causes glomerulonephritis. The present text is an analysis of the impact of immune complex formation on renal pathology and contains retrospective clinical data of our own hospital obtained on 192 patients undergoing diagnostic renal biopsy.

Characterization of Raji cell binding IgG in patients with metastatic breast cancer

The aim of the present study was to isolate and characterize the immune complexes detected by the Raji cell assay in metastatic breast cancer. However, the Raji cell binding material could not be separated from monomeric IgG by Sephacryl S-300 gel chromatography in any of the 16 sera investigated. The parallel elution profile of monomeric IgG and the Raji cell binding activity suggested that anti-Raji cell antibodies, rather than immune complexes of low molecular weight, were present in these sera. This was further substantiated by pepsin digestion of the Raji cell binding IgG fractions. The binding of F(ab')2 fragments was quantitatively comparable to the binding of undigested IgG, and the bound F(ab')2 fragments could be visualized by immunofluorescence at the cell membrane. The presence of antibodies against Raji cells was further confirmed by the complement-dependent cytotoxicity assay. These antibodies did not react with untransformed lymphocytes and there was no correlation with anti-Epstein-Barr virus antibodies. The incidence of cytotoxic anti-Raji cell antibodies in breast cancer was 12% compared to 20% in malignant lymphoma, to 0% in normals and patients with degenerative cardiovascular diseases, and to 5% in patients with auto-immune diseases.

Lymphocyte subpopulations in Spanish parenteral drug addicts

Lymphocyte subpopulations were studied in 29 symptom-free Spanish prisoners who were active parenteral drug abusers. In 16/29 drug addicts (55%) the helper-inducer/suppressor-cytotoxic ratio (Leu 3a/Leu 2a) was less than 1. None of these 16 patients had lymphopenia and only 2 had a reduction in the number of Leu 3a cells. In drug addicts the number of lymphocytes (p less than 0.01) and the number and percentage of Leu 2a cells (p less than 0.001) were significantly raised. The addicts also had a higher absolute number of T cells when measured by their ability to react with the Leu 4 antibody (p less than 0.01). However, the E-rosette forming cells were significantly reduced. Thus the E-rosette test may lead to an overestimation of "null" cells. Furthermore drug addicts had a higher percentage (p less than 0.001) of Leu 7 positive cells (NK and K cells), but a normal percentage of B and phagocytic cells. Five drug addicts had generalized persistent lymphadenopathies, and 2 had skin anergy. We believe that most of the immunologic abnormalities seen in these apparently healthy drug abusers can be explained by an antigenic overload.

Effectiveness of cyclosporin therapy for Behçet's disease

Behcet's disease is a clinical entity with mouth and genital ulcers, skin lesions, and both anterior and posterior uveitis as its major criteria. It has been theorized that Behcet's disease is immune complex mediated, and is characterized by multiple attacks which often lead to severe visual handicap. Behcet's disease patients with severe ocular involvement and cytotoxic and/or systemic corticosteroid agent failures were treated with cyclosporin (CsA). CsA therapy effectively abrogated the acute phase of the ocular attack and either totally prevented, or markedly reduced, the recurrences of these attacks. Generally, patients tolerated the medication well; occasionally however, renal toxicity secondary to cyclosporin therapy prevented prescription of a maximally effective therapeutic dose of the drug. CsA levels in plasma were dose-dependent for each patient, but the dosage per kg of CsA needed to obtain a specific plasma level varied greatly from patient to patient. Circulating immune complex levels were not universally elevated during the acute ocular attack. However, increases in circulating immune complex concentrations were noted after treatment with CsA was begun and the disease became clinically inactive. These data, as well as the effectiveness of CsA, an agent with predominantly anti-T cell effects, raise a question as to whether circulating immune complexes are centrally relevant to the pathogenesis of this disorder, and if T cell mediation of this disease must be contemplated.

Nephrotic syndrome in two patients with cured Hodgkin's disease

Two cases of lipoid nephrosis (minimal change glomerulonephritis) in patients cured of Hodgkin's disease are reported and the literature is reviewed. Cases reported to date have shown a close temporal relationship between this renal lesion and the presence of Hodgkin's disease. The patients reported are 11 and 9 years without evidence of active malignancy after successful treatment for Hodgkin's disease. Each had abnormal immunologic parameters, depressed T4 (helper) cells and increased T8 (suppressor) cells, which may predispose to the development of the nephrotic syndrome. However, the advent of this complication is not necessarily a harbinger of recurrent lymphoma.

Fc-specific reticulo-endothelial clearance in systemic lupus erythematosus and glomerulonephritis

Fc-specific reticulo-endothelial (R-E) clearance was determined in control subjects (n = 11) and in patients with immune complex (IC) glomerulonephritis (n = 22) and systemic lupus erythematosus (SLE) nephritis (n = 10). Clearance (t1/2) depended on the removal of autologous erythrocytes labeled with 51chromium and sensitized with anti-D IgG by fixed splenic macrophages bearing receptors for the Fc portion of the IgG molecule. A significant difference in clearance rates was demonstrated between normal individuals with and without the HLA-B8, DR3 haplotype. Marked clearance defects were found in SLE (8/10), and t1/2 correlated with the levels of circulating IC. Delayed clearance was also observed in 6/11 patients with IgA nephropathy or Henoch-Schönlein purpura and in 4/11 patients with membranous nephropathy (MN). No correlation was found between circulating IC levels and t1/2 in these diseases. Clearance defects in these patients did not correlate with the presence of the HLA-B8, DR3 haplotype. This study demonstrates that some patients with IC glomerulonephritis have defective Fc-mediated clearance that does not appear to be secondary to IC blockade.

An extended C1q-binding assay using lactoperoxidase- and chloramine-T-iodinated C1q. Immediate distinction between immune-aggregate-mediated and non-immune-aggregate-mediated C1q binding

An extension of the C1q-binding assay for the detection of immune-aggregate-mediated and non-immune-aggregate-mediated C1q binding is reported. The assay involves the use of two different C1q preparations, one radioiodinated by means of lactoperoxidase (LPO-125I-C1q) and the other by means of chloramine-T (CT-125I-C1q). The treatment with CT for 20 min at room temperature before iodination for 1 min led to abolishment of the C1q-binding capacities to complexed IgG: approximately 50% of LPO-125I-C1q but only 2% of CT-125I-C1q bound to 80 micrograms/ml of IgG forming part of tetanus toxoid/anti-tetanus toxoid complexes or to 200 micrograms/ml of heat-aggregated human gamma globulin. Similar results were obtained with staphylococcal protein-A-aggregated IgG. CT-treated C1q was haemolytically inactive. In contrast to the results with complexed IgG, CT treatment did not markedly reduce binding capacities of C1q to heparin: approximately 55% of LPO- and CT-125I-C1q were bound by 127 U/ml of commercial heparin in normal human serum. Both C1q preparations bound to a comparable extent to fibronectin, fibrinogen, and various bacterial endotoxins. When the LPO- and CT-125I-C1q-binding patterns obtained on serum samples from patients with systemic lupus erythematosus, rheumatoid arthritis, or essential mixed cryoglobulinaemia were compared with binding patterns observed using laboratory reactants, an immediate detection of non-immune-aggregate-mediated C1q binding became possible.

A simple method for determining polymeric IgA-containing immune complexes

A simplified assay to measure polymeric IgA-immune complexes in biological fluids is described. The assay is based upon the specific binding of a secretory component for polymeric IgA. In the first step, multimeric IgA (monomeric and polymeric) immune complexes are determined by the standard Raji cell assay. Secondly, labeled secretory component added to the assay is bound to polymeric IgA-immune complexes previously fixed to Raji cells, but not to monomeric IgA immune complexes. To avoid false positives due to possible complement-fixing IgM immune complexes, prior IgM immunoadsorption is performed. Using anti-IgM antiserum coupled to CNBr-activated Sepharose 4B this step is not time-consuming. Polymeric IgA has a low affinity constant and binds weakly to Raji cells, as Scatchard analysis of the data shows. Thus, polymeric IgA immune complexes do not bind to Raji cells directly through Fc receptors, but through complement breakdown products, as with IgG-immune complexes. Using this method, we have been successful in detecting specific polymeric-IgA immune complexes in patients with IgA nephropathy (Berger's disease) and alcoholic liver disease, as well as in normal subjects after meals of high protein content. This new, simple, rapid and reproducible assay might help to study the physiopathological role of polymeric IgA immune complexes in humans and animals.

Dietary gluten challenge does not influence the levels of circulating immune complexes in patients with dermatitis herpetiformis

To examine the relationship between the gluten-sensitive enteropathy (GSE) and IgA circulating immune complexes (CIC) in dermatitis herpetiformis (DH) a series of dietary gluten-challenge studies were performed in patients with DH and patients with ordinary GSE. Serial serum samples were monitored for IgA-, IgG-, and IgM-containing CIC levels. In the first study, 9 DH patients and 5 controls were fed 20 g of gluten flour as a breakfast meal on 1 of 2 consecutive study days. DH patients did not develop or increase their levels of CIC after gluten-challenge or gluten-free meals. There was no significant difference between the DH patients and the control group in regard to development of CIC. To evaluate the effect of dietary gluten in another form, 8 DH patients were given meals containing 100 g of boiled Canadian cracked wheat. Two patients with ordinary GSE were also challenged with cracked wheat. Again there was no elevation or induction of CIC above baseline determinations by gluten-challenge meals. These studies suggest that dietary gluten does not induce the formation of CIC in patients with DH.

Circulating IgA immune complexes in patients with psoriasis

The sera of 21 patients with psoriasis were examined for the presence of IgA-containing circulating immune complexes (CIC) using the Raji IgA radioimmunoassay. In addition, the Raji IgG radioimmunoassay and 125I-Clq binding assay were used to detect IgG- and IgM-containing CIC. Twenty-five patients with other hyperkeratotic skin disorders were studied as controls. Patients were studied before institution of systemic therapy with etretinate (20 patients) or 13-cis-retinoic acid (1 patient). In addition, sera of 15 of the patients treated with etretinate were studied before, during, and after therapy. The extent of pretreatment disease involvement as well as response to therapy were evaluated in a blinded fashion. Fourteen of 21 (67%) patients with psoriasis had evidence of IgA-containing CIC at some time during the course of their disease, as compared to only 1 of 25 patients with other hyperkeratotic skin disorders. In contrast, only 2 of 19 (11%) had evidence of IgG-containing CIC using the Raji IgG assay, and only 1 of 19 (5%) had evidence of IgG- or IgM-containing CIC using the 125I-Clq binding assay. A positive correlation was found between the extent of pretreatment disease involvement and the level of IgA-containing CIC by linear regression analysis (p = 0.01). There was, however, no correlation between clinical improvement and the presence or level of IgA-containing CIC in 15 patients followed during therapy. Sucrose density gradient analysis of the IgA-containing CIC found in 2 of these patients demonstrated IgA-containing CIC in the 9S to 13S region. The finding of IgA-containing CIC in a significant number of patients with psoriasis and the relative absence of IgG- or IgM-containing CIC suggest that IgA-containing CIC may play a role in psoriasis. The lack of correlation with clinical improvement, however, suggests these IgA-containing CIC are not directly related to the cutaneous manifestations of psoriasis, but may be important in the modification of immune or inflammatory responses in these patients.

IgA-containing circulating immune complexes in patients with igA nephropathy

The role of circulating immune complexes in the pathogenesis of IgA nephropathy (Berger's disease) is controversial. Previous studies have shown that a minority of these patients have immune complexes, but the methods used have been able to detect only IgG- or IgM-containing circulating immune complexes. Using a sensitive specific Raji cell radioimmunoassay for IgA-containing circulating immune complexes, we have examined serum specimens from 12 patients with IgA nephropathy for the presence of IgA-containing circulating immune complexes. In addition, the Raji cell IgG assay and the 125I-C1q binding assay were used for the detection of IgG- or IgM-containing circulating immune complexes. Purified monoclonal antibodies against human IgA1 and IgA2 were used to determine the subclass of IgA present in renal biopsy specimens from five of these patients. Six of 12 (50 percent) patients had IgA-containing circulating immune complexes, whereas only two of 12 (17 percent) had positive results in the Raji IgG assay and one of 12 (8 percent) in the 125I-C1q binding assay. There was no correlation between serum IgA, C3 C4, or factor B levels and the presence or level of IgA-containing circulating immune complexes. None of the three patients with renal failure had circulating immune complexes of any type. Of the seven patents with disease duration of two years or less, five (71 percent) had IgA-containing circulating immune complexes and three (43 percent) had IgG- or IgM-containing complexes. In all five renal biopsy specimens examined for IgA subclass, diffuse heavy, mesangial deposits of IgA1 were seen, whereas IgA2 staining was absent or present in only trace amounts. These findings suggest that IgA1 is the predominant antibody in renal biopsy specimens from patients with IgA nephropathy. The finding of IgA-containing circulating immune complexes in these patients--and their more frequent occurrence in patients with early stages of the disease--suggests that IgA-containing circulating immune complexes may play a role in the pathogenesis of IgA nephropathy.

C1q binding and Raji immune complex assays: a comparison using defined immunoglobulin aggregates

Aggregated IgG is frequently employed as a standard in systems for the measurement of immune complexes in man and animals. In this paper aggregates prepared by heat or alkali denaturation of human IgG were fractionated by column chromatography through LKB AcA 22 Ultrogel. Heat aggregation yields preparations containing considerably more monomer than alkali treatment (47% and 6.3% respectively). The bulk of aggregated material prepared by both methods was of size 19 S or greater. Smaller aggregates were present in assayable quantities only in the alkali aggregated material. The sized fractions of aggregates IgG were tested in the presence of a human complement source for their efficiency in the C1q binding and Raji radioimmunoassay for immune complexes. Both techniques efficiently measured large aggregates (greater than or equal to 19 S) but the C1q binding assay measured smaller material with greater efficiency than did the Raji cell assay. Neither technique detected monomeric IgG. The date presented is relevant to the binding characteristics of the 2 assay systems studied and suggests that when used together they are capable of measuring immune complexes present over a wide range of sizes.

Antibody-mediated cellular cytotoxicity against Raji cells ADCC(Raji): evaluation of false positives in the detection of circulating immune complexes by Raji-cell assay

Raji-cell radioimmunoassay is a very sensitive and reproducible method for the detection of circulating immune complexes. Using a complement-independent, antibody-dependent cellular cytotoxicity assay against 51Cr-labeled Raji cells, there is no correlation between activity against Raji cells and positivity in Raji-cell radioimmunoassay for circulating immune complexes in three sets of sera (from renal transplantation patients, multiparous women, and patients suffering from systemic lupus erythematosus). We conclude that IgG antibodies to Raji membranes are not a significant cause of false-positive results in circulating immune complexes as detected by Raji-cell radioimmunoassay.

Circulating immune complexes in idiopathic glomerular disease

Circulating immune complexes (CIC) could be found in the majority of 271 sera from 131 patients with idiopathic minimal change, membranous and mesangial proliferative glomerulonephritis when a combination of CIC assays detecting different properties of CIC were used. In neither individual patients nor in any of the three groups as a whole did CIC levels reflect the state of the renal lesion. No correlation was found between the class of immunoglobulin in the CIC and that deposited in the kidney. With the exception of minimal change disease in which non-C1q binding IgG CIC predominated, a range of CIC was found in the patients examined. The pattern of CIC detected did not allow different forms of renal disease to be distinguished. IgA CIC could be found in mesangial proliferative glomerulonephritis both with and without IgA deposition and in some patients with membranous and minimal change disease, as well as in a high proportion of sera from 12 patients with the Henoch-Schönlein syndrome. CIC size was estimated in six patients, but only in one did a specific size of complex predominate. The CIC which may be found in the majority of sera from patients with idiopathic glomerulonepohritis provide little information of clinical value; no direct relationship can be demonstrated between the CIC found and the renal lesion.

Circulating immune complexes in membranoproliferative glomerulonephritis

Circulating immune complexes (CIC), measured by the solid-phase Clq method, were found to be in abnormal concentration in about half of 39 patients with membranoproliferative glomerulonephritis (MPGN). In contrast, they were present, usually in higher concentration, in nearly all patients with active lupus nephritis. Correlations between clinical course and CIC levels in patients with MPGN showed that complexes were always present when the disease was mild or "silent," but when renal impairment developed or was incipient, complexes were nearly always absent. In patients with disease of intermediate severity, characterized by definite proteinuria but without renal impairment, 50% had complexes. The presence of complexes when glomerular abnormality is relatively slight could be interpreted as indicating that the complexes measured were not nephritogenic, or that they program subsequent events that augment glomerular injury in the absence of complexes. The measurement of CIC in MPGN appears to have minimal value both in diagnosis and in determining prognosis.

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.

Studies of the pathogenesis of interstitial cystitis, obstructive uropathy, and intestinal malabsorption in a patient with systemic lupus erythematosus

A patient with systemic lupus erythematosus (SLE) is described who displayed the unusual extraglomerular syndromes of interstitial cystitis with obstructive uropathy and severe secretory-type diarrhea with intestinal malabsorption. Pathologic investigations into the nature of these events revealed immunofluorescent deposits in blood vessel walls of the small intestine and urinary bladder. The patient's malabsorption state and cystitis with urinary obstruction regressed with therapy of the SLE. We are postulating that immune complexes from the circulation may deposit in blood vessel walls, and may be responsible for tissue injury in these sites and the clinical manifestations of this patient.

Defective Fc-receptor functions associated with the HLA-B8/DRw3 haplotype: studies in patients with dermatitis herpetiformis and normal subjects

Dermatitis herpetiformis is associated with the HLA-B8/DRw3 haplotype in over 90 per cent of patients, and various percentages have been reported to have circulating immune complexes. Since removal of immune complexes from the circulation is thought to depend on the Fc-receptor function of tissue macrophages, we studied this function by measuring the clearance of IgG-sensitized autologous erythrocytes in 16 patients with dermatitis herpetiformis, in normal controls with the HLA-B8/DRw3 haplotype, and in randomly selected controls. All patients were HLA-B8 positive, and all of 12 patients tested were HLA-DRw3 positive. Erythrocyte clearance was reduced in eight of the 16 patients, but did not correlate with immune-complex levels. Four of eight controls with HLA-B8/DRw3 also had delayed Fc-receptor-mediated clearance as compared with normal controls. In addition, both patients and HLA-B8/DRw3-positive controls had decreased percentages and total numbers of T cells bearing Fc receptors for IgG. These findings indicate a functional Fc-receptor defect associated with the HLA-B8/DRw3 antigens.

Immunological function in glomerulonephritis

Aspects of humoral and cellular immunity and of the complement system were examined in 44 patients with glomerulonephritis, and in control subjects. A number of patients with glomerulonephritis were shown to have evidence of altered immunity which may reflect underlying mechanisms of glomerular injury. Mesangial IgA glomerulonephritis was associated with elevation of serum IgA levels (P less than 0 . 001), and focal sclerosing glomerulonephritis with raised serum IgM (P less than 0 . 001). Serum IgG levels were abnormal in 15 patients with glomerulonephritis. The haemagglutinating antibody response to tetanus toxoid was reduced in patients compared with controls. Levels of serum complement components were increased, with some exceptions, and C-reactive protein levels were also significantly raised (P less than 0.001), findings consistent with an ongoing inflammatory process. No impairment in response to recall antigens or sensitisation to dinitrochlorobenzene was found, but phytohaemagglutinin induced lymphocyte transformation was reduced in some forms of the disease.

Raji cell assay for immune complexes. Evidence for detection of Raji-directed immunoglobulin G antibody in sera from patients with systemic lupus erythematosus

We asked whether binding of human immunoglobulin (Ig)G antibody reacting with Raji cells could be distinguished from binding of IgG immune complexes. Using a standard Raji assay employing 125I-IgG goat anti-human Fc gamma, we found that digestion of Raji cells with pronase reduced by 95% their ability to bind complement-fixed aggregated human gamma globulin and complement-fixed tetanus toxoid-antitetanus toxin complexes. However, binding at 37 degrees C of IgG from the sera of 16 patients with systemic lupus erythematosus (SLE) to pronase-digested Raji cells was reduced much less consistently and extensively (9-100% reduction; mean reduction of 51%). In more detailed studies of two SLE sera, sucrose density gradient centrifugation showed that greater than 50% of the IgG binding to undigested Raji cells sedimented in the 7S region. Pepsin digestion of immunoglobulin fractions from four SLE sera caused a reduction in SLE IgG binding to undigested Raji cells when detected with 125I anti-Fc gamma, but an increase when binding was detected with 125I-anti-Fab, suggesting that substantial SLE IgG can bind through F(ab')2 regions. Binding of IgG from SLE sera was not directed at neoantigenic sites induced by pronase digestion because binding activity was adsorbed with undigested cells as readily as with digested cells. Moreover, sera from 10 SLE patients that had negative Raji assays contained no IgG that bound to pronase-digested Raji cells. We conclude that much of the IgG bound at 37 degrees C to Raji cells from the sera of many patients with SLE does not represent immune complexes but is probably antibody directed toward sites on the Raji cell.

The ER-rosette inhibition assay as a test for immune complexes

Soluble transferrin-anti-transferrin (TAT) complexes were shown by EA-rosette inhibition assay to block human lymphocyte receptors for the Fc of reacted IgG (Fc gamma) in vitro. These complexes, which provide a convenient and controlled source of Fc gamma receptor blocking material, were found to inhibit EA-rosette formation over a wide range of antigen: antibody ratios. Complexes were detected at both 37 degrees C and 4 degrees C although the range and sensitivity of the assay was markedly increased at 4 degrees C. The inhibitory capacity of TAT complexes was lost on pre-incubation with normal human serum suggesting that only non-complement fixing complexes are detected by EA-rosette inhibition. "False positive" inhibition by antilymphocyte antibodies occurs at 37 degrees C but not at 4 degrees C. Partial automation of the assay was achieved by calibrating a Coulter counter for rosette counting, thus obviating the requirement for tedious and subjective microscopic determinations.

In situ formation of subepithelial glomerular immune complexes in passive serum sickness

Epimembranous glomerular deposition of circulating immune complexes in considered to be the pathogenesis of immune complex glomerulonephritis, based on experiments in serum sickness glomerulopathy. A subepithelial localization of immune aggregates, however, was never obtained after the intravenous injection of preformed immune complexes. Recent studies on heterologous immune complex glomerulonephritis provide evidence of in situ formation of subepithelial glomerular immune complex aggregates as a second pathogenetic mechanism. We investigated the existence of a comparable mechanism in a serum sickness model of glomerulonephritis. A passive immune complex glomerulopathy involving lysozyme/antilysozyme and bovine serum albumin (BSA)/anti-BSA was used to investigate this thesis. Alternating perfusion of a kidney with antigen and antibody resulted in a granular deposition of both components along the glomerular basement membrane (GBM). The deposits of immune aggregates were localized exclusively along the epithelial side of the GBM and were still present 3 days after the perfusion. Control perfusions with preformed immune complexes or with either BSA or anti-BSA alone did not result in subepithelial deposition. Conclusion. The alternating excess of antigen and antibody in the circulation might result in in situ formation of immune complexes localized at the epithelial side of the GBM.

Is autoimmunity a common denominator in immune complex diseases?

In normal circumstances, antibodies reactive with native DNA appear in the plasma during the course of many clinical conditions associated with inflammation. These antibodies seem to be elaborated in response to the release of exceptional amounts of DNA by nucleated cells. As a result, DNA/anti-DNA complexes can be demonstrated in the cryoprecipitable fraction of plasma from patients with various inflammatory diseases. A significant proportion of these immune complexes contain low-molecular-weight polynucleotide antigens. These polynucleotides are derived from DNA which has been degraded by plasma DNAase. Because of the digestion of DNA in the plasma a spectrum of antigen/antibody complexes forms. While large, relatively insoluble complexes would be expected to be rapidly cleared by the reticuloendothelial system, low-molecular-weight complexes are removed more slowly. It is proposed that the action of plasma DNAase upon both free and immune bound-DNA can lead to a preponderance of small, soluble, polynucleotide/anti-DNA complexes. Under appropriate conditions of vascular permeability, these soluble complexes may be deposited in vessel walls. Hence, regardless of the initiating infectious or inflammatory agent, polynucleotide antigen/anti-DNA antibody complexes form and can result in immune-mediated inflammatory phenomena in diverse disease states.

The detection of immune complexes of different immunoglobulin class

Immune complexes were detected in 51 sera from patients with a variety of immunological diseases; 14 systemic lupus erythematosus (SLE); 14 infectious mononucleosis (IM); 12 rheumatoid arthritis (RA) and 11 subacute bacterial endocarditis (SBE). Three methods were used to detect complexes: the fluid--phase Clq binding assay (Clq.BA); the solid--phaseClq binding assay (Clq.SP) and the Raji cell radio-immunoassay (RIA). Modification of the Clq.SP and the Raji cell RIA by use of monospecific antisera to immunoglobulins G, A and M enabled the class of antibody in the immune complexes to be determined. Antibodies of all three classes were found in each disease, the predominant ones being IgG and IgM in SLE and SBE, IgM and IgA in RA and IgM in IM.

Immune complexes in diabetes mellitus

Sera from 86 well controlled diabetics were examined for the presence of immune complexes. Thirty-six patients were receiving standard insulins, 19 monocomponent preparations, 24 oral hypoglycaemic agents and seven dietary restriction alone. Three methods were used to detect complexes: measurement of complement components, a Clq binding assay (BA) and the Raji cell radioimmunoassay (RIA). Complement components were normal in all patients. Eleven (31%) of the group on standard insulins had a positive Raji cell RIA; none had an abnormal Clq-BA. One patient on monocomponent therapy had a mildly positive Raji cell RIA; Clq-BA was negative in each patient of this group. Thirteen (54%) of the patients on oral hypoglycaemic agents were positive on one or both assays while one patient on diet alone was abnormal on both assays. These data show that immune complex production is common in both insulin-requiring and non-insulin-requiring diabetics and that this phenomenon is strikingly less frequent in patients on monocomponent insulins. Such observations could bear relevance to the pathogenesis of microvascular complications in diabetes.