Liliane Intrator

Extrahepatic Immunologic Manifestations in Chronic Hepatitis C and Hepatitis C Virus Serotypes

Extrahepatic immunologic abnormalities have been shown to occur frequently in patients with chronic hepatitis C virus (HCV) infection. Hepatitis C virus now appears to cause those cases of mixed cryoglobulinemia that were previously considered essential [1-5]. Indeed, HCV RNA has been detected in the serum specimens of about 90% of patients with essential mixed cryoglobulinemia [1, 2, 4]. In addition, cryoglobulin is found, usually at low levels, in the serum specimens of one third to one half of patients with chronic hepatitis C [6, 7]; rheumatoid factor, which may play a role in cryoglobulinemia, is present in the serum specimens of about 70% of patients [6]. Various autoantibodies have been seen in the serum of 40% to 50% of patients with chronic HCV infection [6, 8], and HCV has been associated with cases of autoimmune thyroiditis [9]. Salivary gland lesions, characterized by lymphocytic capillaritis, are seen in about half of patients and are sometimes associated with lymphocytic sialadenitis resembling that of the Sjogren syndrome [6]. Finally, HCV may cause the chronic liver disease frequently associated with lichen planus [10]. Recently, sequences of different HCV variants were classified into different genotypes on the basis of overall sequence similarity [11-22]. A consensus nomenclature for HCV genotypes has been proposed [23], in which the six HCV genotypes identified so far are numbered in the order of their discovery. Within each genotype, subtypes have been identified by lower case letters, which are also given in order of discovery [23]. Correspondence among the classifications reported so far is presented in Table 1. Different techniques for determining HCV genotype have been developed in recent months. Currently, in addition to sequencing the genome, investigators can use three techniques based on the polymerase chain reaction (PCR). The technique described by Okamoto and colleagues [24, 25] is based on a nested PCR amplification of the HCV genome and uses primers located in the core region: The first round of PCR uses a pair of universal (non-type-specific) primers and the second uses a pair of type-specific primers. The method of McOmish and colleagues [17, 18] is based on PCR amplification of the 5 noncoding region of the genome done with a pair of universal primers, followed by enzymatic digestion of the amplified products and analysis of their restriction fragment length polymorphism. Stuyver and colleagues described a line probe assay for the determination of HCV genotypes [22], in which a PCR amplification is done using universal primers located in the 5 noncoding region of the genome. This is followed by hybridization of the amplified products to oligonucleotide probes attached as parallel bands on nitrocellulose strips. On the other hand, a serotyping immunoenzymatic assay to detect genotype-specific antibodies directed to epitopes encoded by the NS4 region of the HCV genome has been developed [26]. This technique, in its present form, allows the differentiation of HCV serotypes 1, 2, and 3, which correspond to HCV genotypes 1, 2, and 3 in the consensus nomenclature [23]. Table 1. Correspondence between the Major Published Classification Systems for Hepatitis C Virus Genotypes* Several studies indicate that particular HCV genotypes are associated with more severe liver disease and poorer response to interferon- therapy [27-30]. The factors determining immunologic abnormalities in patients with chronic hepatitis C are largely unknown. We used a serotyping assay to study whether the occurrence of extrahepatic immunologic abnormalities in patients with chronic hepatitis C is serotype dependent. Methods Patients Fifty-nine consecutive patients with chronic hepatitis C were prospectively studied. Thirty-four were men and 25 were women; their mean age was 52 years (range, 18 to 77 years). In all cases, the diagnosis of chronic hepatitis C was based on long-term elevation of serum alanine aminotransferase levels in the blood, positive serologic markers of HCV infection (found using second-generation enzyme-linked immunosorbent assay and recombinant immunoblot assay, Ortho Diagnostic Systems, Raritan, New Jersey), and the absence of any other cause of chronic liver disease. Specimens obtained by percutaneous liver biopsy showed chronic active hepatitis in all 56 patients tested and associated cirrhosis in 15 of the 56 (27%). Before any treatment was given, serum specimens were tested for cryoglobulin, rheumatoid factor, and many antitissue antibodies, and biopsy of labial salivary glands was done. Hepatitis C virus serotype was determined in all patients by immunoenzymatic assay. Study Methods Detection of Cryoglobulinemia Venous blood (20 mL) was taken from fasting patients in a room at 37 C, allowed to clot at this temperature, and then separated by centrifugation. After centrifugation, the supernatant was removed from the serum, incubated at 4 C for 8 days, and examined daily for cryoprecipitation. Detection of Rheumatoid Factor Rheumatoid factor was measured using a nephelometer analyzer (BNA, Behring, Marburg, Germany); polystyrene particles coated with human globulin were agglutinated when mixed with samples containing rheumatoid factor. Normal values were those less than 18 IU/mL. Detection of Autoantibodies Antinuclear, anti-smooth muscle, type 1 anti-liver-kidney microsomal (anti-LKM1), and antimitochondrial antibodies were detected by indirect immunofluorescence using air-dried cryostat sections from rat or mouse livers and kidneys and HEp-2 cells (Kallestad, Chaska, Minnesota) as substrates. Antithyroid microsomal antibodies were detected by indirect immunofluorescence using surgical specimens of human thyrotoxic thyroid as substrate. In all cases, the classic Weller and Coon indirect immunofluorescence method was used with fluorescein-labeled goat immunoglobulin directed to IgG, IgA, and IgM (Pasteur Diagnostics, Marnes la Coquette, France) as a second layer [31]. The serum specimens were tested undiluted for anti-DNA antibodies, at a 1/5 dilution for antimicrosomal antibodies, and at a 1/10 dilution for other antibodies. The titers were established using increasing dilutions up to 1/2560. Antithyroglobulin antibodies were detected using an hemagglutination kit (Thymune-T, Wellcome Diagnostics, Dartford, United Kingdom). Labial Salivary Gland Examination All biopsies were done in macroscopically normal mucosa. The samples were fixed in Bouin fluid, embedded in paraffin, and stained with hematoxylin-eosin-safranin. All sections were examined blind by two pathologists and graded according to the Chisholm and Mason classification system [32]. Determination of Serotypes The 59 serum specimens in our study were tested for the presence of serotype-specific antibodies using the recently developed enzyme immunoassay [26]. A series of eight branched peptides, synthesized from two antigenic regions of HCV genotypes 1, 2, and 3, were used to coat polypropylene microtiter wells overnight at 4 C. After washing, the wells were blocked with 150 L of blocking solution (phosphate-buffered saline, 0.1% Tween 20, and 2% bovine serum albumin) for 1 hour at room temperature. Blocking assays were done using mixes of type-specific peptides at a final concentration of 1 mg/mL (for example, 100:1 excess over that used to coat the wells). Plasma specimens from the 59 patients were diluted in the blocking solution and 100 L were added to antigen-coated and blocked wells. The first incubation was done overnight at 4 C. Plates were washed four times in phosphate-buffered saline and 0.1% Tween 20 and then incubated with horseradish peroxidase-conjugated anti-human IgG (1/20 000 in phosphate-buffered saline and 0.1% Tween 20 for 1 hour at room temperature). The plates were finally washed four times in phosphate-buffered saline and 0.1% Tween 20 and incubated with substrate (50 g of O-phenylenediamine per milliliter and 0.1% H2O2 [30 volumes] for 30 minutes in the dark at room temperature). Optical densities were read at 490 nm; values ranged from 100 to 2000 mU. Results Prevalence of Immunologic Abnormalities Our results are presented in Table 2. Cryoglobulin was found in the serum specimens of 20 of the 56 patients tested (36%), and rheumatoid factor was present at abnormal levels in 42 of the 59 patients (71%). Table 2. Prevalence of the Different Immunologic Abnormalities according to Hepatitis C Virus Serotype At least one type of antitissue antibody was detected in the serum specimens of 24 of the 59 patients (41%). Thirteen patients (22%) had serum antinuclear antibodies and 13 (22%) had anti-smooth muscle antibodies at a significant titer (greater than 1/40). Anti-LKM1 antibodies were found in 3 patients (5%) and antithyroid antibodies were found in 5 (8%); 4 of these 5 had antithyroglobulin and 1 had antithyroid microsomes. No antimitochondrial antibodies were found. Labial salivary gland biopsies were done in those 49 of the 59 patients who had no contraindication and who gave informed consent; lesions were found in 24 of them (49%). In all patients, these lesions were characterized by lymphocytic capillaritis, as previously described [6]. In 7 patients (14%), they were associated with more severe lesions, grades 3 and 4 by the Chisholm and Mason classification (lymphocytic sialadenitis) [32], and resembled the lymphocytic sialadenitis of the Sjogren syndrome (14%). Only one of the patients with salivary gland lesions had a mild case of the ocular sicca syndrome shown by the Schirmer test. The prevalences of the different immunologic abnormalities did not vary significantly according to the presence of cirrhotic findings in liver specimens. Hepatitis C Virus Serotypes Thirty-five of the 59 patients (59%) were infected with HCV serotype 1, 6 (10%) were infected with serotype 2, and 7 (12%) were infected with serotype 3 (serotypes are here described using the proposed consensus nomenclature [23]). Two

Human Serum Facilitates Hepatitis C Virus Infection, and Neutralizing Responses Inversely Correlate with Viral Replication Kinetics at the Acute Phase of Hepatitis C Virus Infection

ABSTRACT The factors leading to spontaneous clearance of hepatitis C virus (HCV) or to viral persistence are elusive. Understanding virus-host interactions that enable acute HCV clearance is key to the development of more effective therapeutic and prophylactic strategies. Here, using a sensitive neutralization assay based on infectious HCV pseudoparticles (HCVpp), we have studied the kinetics of humoral responses in a cohort of acute-phase patients infected during a single nosocomial outbreak in a hemodialysis center. The 17 patients were monitored for the spontaneous outcome of HCV infection for 6 months before a treatment decision was made. Blood samples were taken frequently (15 ± 4 per patient). Phylogenetic analysis of the predominant virus(es) revealed infection by only one of two genotype 1b strains. While all patients seroconverted, their sera induced two opposing effects in HCVpp infection assays: inhibition and facilitation. Furthermore, the ability of sera to facilitate or inhibit infection correlated with the presence of either infecting HCV strain and divided the patients into two groups. In group 1, the progressive emergence of a relatively strong neutralizing response correlated with a fluctuating decrease in high initial viremia, leading to control of viral replication. Patients in group 2 failed to reduce viremia within the acute phase, and no neutralizing responses were detected despite seroconversion. Strikingly, sera of group 2, as well as naïve sera, facilitated infection by HCVpp displaying HCV glycoproteins from different genotypes and strains, including those retrieved from patients. These results provide new insights into the mechanisms of viral persistence and immune control of viremia.

High-Dose Immunoglobulin Therapy for Severe IgA Nephropathy and Henoch-Schonlein Purpura

IgA nephropathy (IgAN) is characterized by IgA and C3 deposits in the mesangium [1] and is the most common form of primary glomerulonephritis [2]. Chronic renal failure occurs in approximately 25% of patients 10 years after diagnosis and in as many as 40% to 50% after 20 years [2-4]. Idiopathic Henoch-Schonlein purpura (HSP) is a more severe and systemic form of IgAN [4]. The causes of IgAN are still poorly understood. Glomerular damage might be related to deposits of IgA-containing immune complexes [4, 5], resulting from an uncontrolled mucosal immune response to chronic exposure to environmental antigens or from an anomaly of the medullary IgA system, which is thought to be a second line of defense against foreign antigens [6]. Studies have identified factors associated with poor outcome, such as heavy proteinuria, hypertension, altered renal function, and high histologic grade [2, 4, 7, 8]. Although renal insufficiency develops slowly in most patients, a subset of patients experiences a more severe disease course that requires dialysis within 1 to 5 years [2-4, 7, 9]. Unfortunately, despite the fact that glomerular injury is immunologically mediated, IgAN and HSP do not respond to steroids and immunosuppressive drugs [3]. We previously reported a partial IgG subclass deficiency (mainly involving IgG1) in proteinuric IgAN and HSP [10]. We postulated that such an IgG imbalance might favor viral and bacterial infections [11, 12], a known trigger of flare-ups in these diseases, or activate noxious isotypic compensatory mechanisms [13]. Because high-dose intravenous immunoglobulins are effective in some human immune-mediated diseases [14], we began a prospective trial of high-dose intravenous immunoglobulins in patients with severe IgAN and HSP who had indicators of poor prognosis. Methods Patients Ten men and one woman were enrolled in the study. The criteria for eligibility were idiopathic IgAN or HSP at histologic stage II/III, III, III/IV, or IV; proteinuria level greater than 2 g/d; and glomerular filtration rate greater than 35 mL/min per 1.73 m2. The local ethics committee approved the trial and all patients gave informed consent. Nine had IgAN and two had HSP. Five patients with IgAN were referred by their general practitioner for heavy proteinuria, whereas the remaining four were referred for severe IgA nephropathy by the nephrology units of two general hospitals. One patient with HSP was found to have nephritis while being treated in the dermatology unit of our institution, and the second was referred to our nephrology unit by his general practitioner for HSP with renal involvement. The median age was 24 years (range, 18 to 36 years). The median time between diagnosis and therapy was 5 months (range, 1 to 18 months) (Table 1). All patients had been treated for focal infections and had tonsillectomy for chronic tonsillitis or for reasons of immunity [15]. Two patients were treated unsuccessfully with high-dose steroids at least 3 months earlier. No patient received nonsteroidal anti-inflammatory drugs in the year before the trial. Nine of the 11 patients were treated for hypertension before entry into the trial, and their blood pressure levels rapidly returned to normal during therapy with -blockers alone (atenolol or betaxolol) or combined with prazosin; these drugs were pursued during the trial. None of the patients had severe hypertension: Results of the fondus oculi, hemogram, and heart ultrasound examinations were normal. Treatment of hypertension did not reverse the decline in renal function, despite prolonged follow-up before immunoglobulin therapy. Nine of the 11 patients had altered renal function (median glomerular filtration rate of the group, 57.5 mL/min per 1.73 m2; range, 39 to 134 mL/min per 1.73 m2). The median monthly rate of renal function decline before therapy was 3.78 mL/min (range, 13.80 to 0 mL/min) (Table 1), with a median total decline in renal function before therapy of 27.5 mL/min (range, 55 to 0 mL/min). All patients had heavy proteinuria (median protein level, 5.20 g/d; range, 2.37 to 10.70 g/d) (Table 1), a high histologic grade (1 with stage II/III; 4 with stage III; 3 with stage III/IV; 3 with stage IV), a high histologic index of activity (median, 5; range, 2 to 10), and a moderate histologic index of sclerosis (median, 4; range, 0 to 9) (Table 1). All had dense IgA and C3 mesangial deposits; four patients also had IgA deposits along the glomerular capillary wall. Immunoglobulin G deposits were absent, whereas mild IgM deposits were found in 5 of the 11 patients. The two patients with HSP also had articular effusion, extensive cutaneous purpura, abdominal pain, and diarrhea. Table 1. Changes in Renal Function and Urinary Variables with Immunoglobulin Therapy* Intervention The patients received 1 g/kg of body weight per day (in a 12-hour infusion) of pepsin-pH 4 intravenous immunoglobulins (Biotransfusion, Roissy, France) on 2 successive days each month for 3 successive months, followed by intramuscular immunoglobulins (Polygamma, 16.5%; Association Nationale pour la Distribution des Fractions Plasmatiques Humaines, Paris, France) at a dose of 0.35 mL/kg of body weight twice each month for another 6 months. To avoid serum sickness related to formation of immune complexes between free circulating environmental antigens and infused IgG, a complication previously reported with IgG deficiency [16], the first intravenous immunoglobulin infusion was preceded by single 3-L plasmapheresis with albumin replacement. We examined patients monthly during their hospital stay for the first 3 months, as outpatients from the third to the eighth month, and in the hospital at the end of the study (ninth month). After the 9-month trial, patients received the same maintenance therapy (0.35 mL/kg of intramuscular immunoglobulins twice each month) and were examined every 3 months as outpatients. Angiotensin-converting-enzyme inhibitors, calcium channel blockers, corticosteroids, and nonsteroidal anti-inflammatory drugs were not allowed during the trial. The patients ate a normal protein diet (1.5 to 2 g/kg per day of protein). Follow-up We assessed clinical, renal, viral, and immunologic tolerance at each visit during the 9-month study period and then every 3 months thereafter. Measurements Renal Histologic Findings Global Histologic Grading: We used the grading system of Lee and associates [7], which requires that at least nine glomeruli be scored. Biopsy specimens were blindly scored in five grades of increasing severity [7], accounting for both cellular proliferation and sclerosis. Stage I corresponded to normal glomeruli or occasional segmental mesangial thickening with or without cellularity. In stage II, fewer than one half of the glomeruli showed localized mesangial proliferation and sclerosis. Stage III was characterized by diffuse mesangial proliferation and thickening with focal and segmental variation, and focal interstitial edema and infiltrates may be present as small crescents and adhesions. In stage IV, marked diffuse mesangial proliferation and sclerosis were evident, with crescents in as many as 45% of the glomeruli. Partial or total glomerulosclerosis was frequently seen as tubular atrophy and interstitial infiltrates. Lesions classified as stage V were the same as in stage IV but more severe. Some biopsy specimens were given intermediate scores. Histologic Activity Index: We noted proliferation of mesangial and epithelial cells blindly using a final scale of 14 points; we required that at least nine glomeruli be examined. In evaluating mesangial cell proliferation, we accounted for the intensity (absent = 0; mild = 1; moderate = 2; severe = 3) and extent of the lesions (no glomeruli affected = 0; <25% of glomeruli = 1; >25% but <50% = 2; >50% but <75% = 3; >75% = 4). We noted epithelial cell proliferation in the same way. Histologic Sclerosis Index: We evaluated two parameters blindly (mesangial plus glomerular sclerosis, and interstitial sclerosis) and required that at least nine glomeruli be scored. Mesangial sclerosis accounted for both the intensity (absent = 0; moderate = 1; severe = 2) and extent of the lesions (no glomeruli affected = 0; <25% of the glomeruli = 1; >25% but <50% = 2; >50% but <75 % = 3; >75% = 4). With regard to interstitial sclerosis, we evaluated interstitial fibrosis on a 2-point scale (absent = 0; moderate = 1; severe = 2) and tubular atrophy in the same way (absent = 0; moderate = 1; severe = 2). Immunofluorescence Studies: We used a direct immunofluorescence technique with fluorescein-labeled goat antisera derived from the same batches (Institut Pasteur, Marnes la coquette, France, and Behring Institut, Marburg, Germany) directed against IgA, IgG, IgM, C1q, C3, and C4. The fluorescence intensity was scored blindly from 0 to 3. Biochemical Measurements of Renal Disease Activity We assayed protein levels at 24 hours using a dye-based method derived from Bradfords technique. We determined the proteinuria selectivity index by studying the IgG:albumin clearance ratio, which we measured using a nephelometer and specific polyclonal antisera (Behring Institut). We measured urinary erythrocyte and leukocyte counts during a 3-hour morning rest period and assayed urinary fibrin-fibrinogen degradation products according to the method of Merskey and Kleiner [17]. Using a specific enzymatic method, we measured plasma creatinine. We assessed global renal function through measurements of creatinine clearance (according to Cockroft and Gault [18]) and an inulin analog clearance (polyfructosan). Because evaluation of renal function decline with both the 1/creatinine ratio and the slope of the glomerular clearance curve was recently criticized (because the decline in renal function is not always linear [19, 20]), we evaluated the rate of renal function decline as follows: loss in glomerular filtration rate during the period studied (mL/min per 1.73 m2) divided by

Specific antiplatelet glycoprotein autoantibodies are associated with the thrombocytopenia of primary antiphospholipid syndrome

Thrombocytopenia is a frequent complication of primary antiphospholipid syndrome (PAPL) and has been attributed to antibodies directed against platelet glycoproteins (Gp) and also to antiphospholipid antibodies. We tested patients with PAPL with and without thrombocytopenia for specific antiplatelet autoantibodies. Platelet autoantibodies were detected by means of platelet immunoassays which included MAIPA with a panel of monoclonal antibodies directed against all the platelet Gps known to be possible targets for platelet autoantibodies. A high prevalence of serum platelet antibodies was found in patients with thrombocytopenia (73%, 11/15 patients) whereas antiplatelet antibody was detected in only one of the 10 control patients (P < 0.01). The antibodies mainly recognized GpIIbIIIa (n = 7), but also CD9 (n = 5), GpIaIIa (n = 4), GpIbIX (n = 3) and GpIV (n = 3). Platelet‐Gp antibodies eluted from the platelet surface had the same reactivity as those found in the original sera from three of the four patients tested, whereas no anticardiolipin activity was found in the platelet eluates, suggesting the absence of cross‐reactivity between anticardiolipin and antiplatlet antibodies. The MAIPA assay was also performed with F(ab′)2 fragments obtained by pepsin digestion of serum IgG from four patients. The same results were obtained with F(ab′)2 fragments and the original serum, demonstrating that platelet antibodies specifically bind in vivo to platelet Gps via their F(ab′)2 fragments. Our results suggest a link between specific platelet antibodies and the thrombocytopenia of PAPL.

Immunomodulation with Low-Dose Immunoglobulins for Moderate IgA Nephropathy and Henoch-Schönlein Purpura

Recently, our group has shown that a 3-month course of intravenous immunoglobulin (2 g/kg/monthly) followed by 6 months of intramuscular immunoglobulins (IMIG, 16.5%, 0.35 ml/kg every 15 days) was able to slow or to stop the decline in the glomerular filtration rate, to reduce proteinuria, hematuria, leukocyturia and the histological index of activity on renal biopsy in patients with severe forms of IgA nephropathy (IGAN) and Henoch-Schönlein purpura (HSP). The aim of this open prospective trial was to evaluate the efficacy and safety of low-dose immunoglobulin therapy in moderate IGAN and HSP with permanent proteinuria. Fourteen patients with moderate IGAN [idiopathic IGAN: n = 11; chronic idiopathic HSP: n = 3] and permanent albuminuria were treated with polyvalent IMIG (16.5%) for 9 months (0.35 ml/kg once a week for 1 month, followed by 0.35 ml/kg every 15 days for a further 8 months). Eligibility criteria in the study were Lee histological stage I, II or III, albuminuria between 300 and 2,000 mg/day and a glomerular filtration rate > 70 ml/min/1.73 m2. IMIG were well tolerated and only 1 patient withdrew from the trial. No viral, renal or immunological side effects were observed. IMIG induced a significant decrease in albuminuria as well as in the histological activity index in the 11 cases in which a follow-up biopsy was performed. There was also a decrease in serum IgA, serum beta 2-microglobulin and IgA immune complex levels, and an increase in serum IgG1 levels. Twelve of the 13 evaluable patients improved during treatment.

Antiphospholipid antibodies in adults with immune thrombocytopenic purpura

To determine the clinical significance of antiphospholipid antibodies (aPL) in patients with immune thrombocytopenic purpura (ITP), anticardiolipin (aCL) (IgG and IgM) and lupus anticoagulant (LA) were sought at diagnosis in 215 ITP adults with platelets <50 × 109/l. aPL (aCL and/or LA) were detected in 55 patients (26%): aCL alone in 39 (18%), aCL and LA in 15 (7%) and LA alone in one (0·5%). LA was significantly associated with high IgG‐aCL levels (P = 0·001). Among age, sex, initial platelet count, bleeding score, acute or chronic ITP outcome, only younger age was significantly associated with LA‐positivity (mean age 29 ± 14 years vs. 45 ± 20 years, P = 0·002). After a median follow‐up of 31 months, 14/215 (7%) patients developed thrombosis (four arterial, 10 venous and/or pulmonary embolism); four of them (29%) had high aCL levels and LA. Multivariate analysis significantly associated thrombosis events only with age [hazard ratio (HR) = 1·6; 95% confidence interval (CI): 1·2–2·4], LA (HR: 9·9; 95% CI: 2·3–43·4) or high IgG‐aCL level (HR: 7·5; 95% CI; 1·8–31·5). Although the thrombosis rate was low, the significant associations between thrombosis and LA or high aCL level suggest that aPL should be tested at ITP diagnosis.

An Increase in Circulating IgA Antibodies to Gliadin in IgA Mesangial Glomerulonephritis

In IgA glomerulonephritis (GN), the pathogenic role of IgA is well documented, but the specificity of these IgA is unknown. Cases of celiac disease associated with IgA GN have been reported and led us to investigate the role of gliadin sensitivity. We measured IgA, IgG and IgM antibodies to gliadin, beta-lactoglobulin and ovalbumin by ELISA (results expressed as optical density; OD) in 27 patients with primary IgA GN, 14 with membranous GN (MGN), 21 with idiopathic nephrotic syndrome (INS) and 21 healthy controls. The normal value for antigliadin IgA was less than 0.650 OD. 19/27 patients with IgA GN had a raised level versus 2/14 in MGN and 2/21 INS (p less than 0.001: IgA GN vs. MGN, INS and controls). Antibodies to beta-lactoglobulin were rarely found and were not more frequent in IgA GN. Cross-reactivity with reticulin was investigated in 16 patients who were serum-positive for IgA antigliadin: no reticulin antibodies were detected by immunofluorescence. Antigliadin IgA are of diagnostic value for distinguishing IgA GN from other GN, with a sensitivity of 70%, a specificity of 89%, a positive predictive value of 83% and a negative one of 79%.