Serum Secretory IgA Research Articles

Effects of Acanthopanax senticosus supplementation on innate immunity and changes of related immune factors in healthy mice.

Modern scientific research has shown that Acanthopanax senticosus (AS) can regulate the innate immunity of healthy animals, thus affecting the health of animals. However, there are few systematic reports on the changes of innate immune indices of healthy animals after consuming AS. The purpose of this project was to study the effect on healthy mice’s innate immunity and changes of related immune factors induced by feeding AS root powder supplementation. The results showed that the killing rate of natural cells increased in a dose-dependent manner in a certain time period. Compared to the control group, the treatment groups (T1, T2 and T3) improved significantly in the innate immune index (lysozyme, β-defensin-2 and duodenal secretory IgA (SIgA) to varying degrees) and induced corresponding changes of immune factors at certain time periods. The correlation between SIgA and IFN-γ in mouse serum was enhanced, and the higher the concentration of AS in the diet, the stronger the correlation was. However, there was no significant difference in growth performance among groups. It is proved that AS supplementation can enhance innate immunity and change several relevant immune factors and cells of healthy mice without affecting growth performance.

Influence of chronic stress on secretory immunity

The study describes the effect of presence of chronic stress caused by living in the combat zone, the concentration of secretory IgA in serum and oral fluid of 23 healthy blood donors living in Donetsk during the period of military conflict. It was found that long-term residents in the conflict zone are characterized by a significant decrease in the concentration of secretory IgA in serum and in oral fluid. At the same time, among the aforementioned group of people there is an increase in the frequency of registration of test subjects with the content of the marker <3 mg/l in serum and <200 mg/l in oral fluid, which is not typical for the persons surveyed during the period of peace. A significant correlation of sIgA with the concentration of the marker in oral fluid in both groups is noted.

IgA- and SIgA anti-PR3 antibodies in serum versus organ involvement and disease activity in PR3-ANCA-associated vasculitis.

Circulating immunoglobulin (Ig)A class anti-neutrophil cytoplasm antibodies (ANCA) directed against proteinase 3 (PR3) have been reported in ANCA-associated vasculitis (AAV) with mucosal involvement. However, secretory IgA (SIgA) PR3-ANCA has not been reported previously. In this study we compared serum levels of SIgA PR3-ANCA and IgA PR3-ANCA with IgG PR3-ANCA in relation to disease characteristics. Among 73 patients with AAV and PR3-ANCA at diagnosis, 84% tested positive for IgG PR3-ANCA, 47% for IgA-ANCA and 36% for SIgA PR3-ANCA at the time of sampling for the present study. IgA and IgG PR3-ANCA were represented similarly among patients with different organ manifestations, i.e. upper airway, lung or kidney at time of sampling. However, SIgA PR3-ANCA was significantly less represented among patients with upper airway involvement. During active disease, the proportions of IgA PR3-ANCA and SIgA PR3-ANCA-positive patients were significantly higher compared to inactive disease. Eight patients were sampled prospectively during 24 months from onset of active disease. In these patients, IgA PR3-ANCA and SIgA PR3-ANCA turned negative more often after remission induction compared to IgG PR3-ANCA. Our findings suggest that serum IgA PR3-ANCA and SIgA PR3-ANCA are related more closely to disease activity in AAV compared to IgG PR3-ANCA. Further studies are required to reveal if this has implications for disease activity monitoring. The mean number of PR3-ANCA isotypes increased along with disease activity, suggesting a global B cell activation during active disease.

Up-Regulation of CysLT2 Receptor Expression and Cysteinyl Leukotrienes-Induced Calcium Signaling By Th2 Cytokines in Human Endothelial Cells

FEBRUARY 2015 AB60 Abstracts S A T U R D A Y 191 Serum Zinc and Secretory IgA Levels Are Important Factors in Children with Food Allergy Yosuke Baba, MD, PhD, Reina Yokota, MD, Hiromi Yagisawa, MD, Susumu Yamazaki, MD, Asuka Ishida, MD, Eisuke Inage, MD, PhD, Mari Mori, MD, PhD, Yoshikazu Ohtsuka, MD, PhD, Toshiaki Shimizu, MD, PhD; Department of Pediatrics and Adolescent Medicine, Juntendo University Faculty of Medicine, Tokyo, Japan, Department of Pediatrics, Juntendo University Shizuoka Hospital, Shizuoka, Japan. RATIONALE: Zinc is an essential nutrient and its deficiency causes malnutrition and results in defects in innate and acquired immune responses. Also, zinc is important for highly proliferating cells, especially in the immune system and influences both innate and acquired immune functions. However, the precise roles and molecular mechanisms of zinc’s function in allergic response have not been clarified. On the other hand, the IgA antibody is massively produced in the intestinal Peyer’s patches, and the secretory IgA (sIgA) plays an important role on mucosal immune responses. It is considered that sIgA regulates the cause of allergic reactions. We studied serum zinc levels and sIgA levels in children with food allergies and studied their relationship with allergy symptoms. METHODS: It is a retrospective study using medical records of infants (from 6 months to 6 years old) who had been admitted to our hospitals. We classified the groups according to the results of physical examinations with or without allergic symptom (eczema, wheezing, food allergy). In addition, we investigated thewhite blood cell counts (eosinophils and basophils) and the serum levels of specific IgE, total IgA, sIgA, TARC (thymus and activation-regulated chemokine), and zinc. RESULTS: Children who were low levels in sIgA and serum zinc have past histories of atopic dermatitis, and their serum levels of specific IgE was significantly higher (p50.013) but their serum IgA level was significantly lower (p50.038) compared with children who does not have allergic symptoms. CONCLUSIONS: Secretory IgA levels and zinc levels are also important to the onset of allergic reactions.

Decreased bacterial diversity characterizes the altered gut microbiota in patients with psoriatic arthritis, resembling dysbiosis in inflammatory bowel disease.

To characterize the diversity and taxonomic relative abundance of the gut microbiota in patients with never-treated, recent-onset psoriatic arthritis (PsA). High-throughput 16S ribosomal RNA pyrosequencing was utilized to compare the community composition of gut microbiota in patients with PsA (n = 16), patients with psoriasis of the skin (n = 15), and healthy, matched control subjects (n = 17). Samples were further assessed for the presence and levels of fecal and serum secretory IgA (sIgA), proinflammatory proteins, and fatty acids. The gut microbiota observed in patients with PsA and patients with skin psoriasis was less diverse when compared to that in healthy controls. This could be attributed to the reduced presence of several taxa. Samples from both patient groups showed a relative decrease in abundance of Coprococcus species, while samples from PsA patients were also characterized by a significant reduction in Akkermansia, Ruminococcus, and Pseudobutyrivibrio. Supernatants of fecal samples from PsA patients revealed an increase in sIgA levels and decrease in RANKL levels. Analysis of fatty acids revealed low fecal quantities of hexanoate and heptanoate in both patients with PsA and patients with psoriasis. Patients with PsA and patients with skin psoriasis had a lower relative abundance of multiple intestinal bacteria. Although some genera were concomitantly decreased in both conditions, PsA samples had a lower abundance of reportedly beneficial taxa. This gut microbiota profile in PsA was similar to that previously described in patients with inflammatory bowel disease and was associated with changes in specific inflammatory proteins unique to this group, and distinct from that in patients with skin psoriasis and healthy controls. Thus, the role of the gut microbiome in the continuum of psoriasis-PsA pathogenesis and the associated immune response merits further study.

Regulation of plasma cell IgA production through the B cell maturation antigen receptor (MUC8P.802)

Abstract B Cell Maturation Antigen (BCMA) is a receptor expressed on plasma cells (PCs) and is important for the survival of long-lived PCs in the bone marrow. Our laboratory has shown that autoimmune-prone mice deficient in BCMA (lpr.BCMA-/-) develop an exacerbated autoimmune phenotype, including increased numbers of PCs, T cells, and serum autoantibody IgG titers. We recently determined that these mice also have increased total and auto-antigen specific serum IgA titers. Because IgA is normally produced in the mucosa-associated lymphoid tissue, this observation suggests a loss of tolerance in the intestinal mucosa. Based on these data, we hypothesized that BCMA signaling regulates homeostasis between commensal bacteria and the protective intestinal IgA response. We found that lpr.BCMA-/- mice have increased serum secretory IgA and commensal-specific IgA levels compared to controls. However, this was not due to increased intestinal permeability as assessed by a serum FITC dextran assay. To determine if commensal bacteria regulate peripheral IgA responses, lpr.BCMA-/- mice were placed on a one month antibiotic regimen. This regimen ameliorated autoimmune disease and reduced IgA-producing PCs, including both autoantibody and commensal-specific IgA. These results suggest that BCMA is important for the regulation of intestinal mucosal tolerance in our models, elucidating a previously unknown role for BCMA in maintaining the balance between commensals and the adaptive immune response.

Improving potency of Chlamydia trachomatis major outer membrane protein muli-epitope DNA vaccine by fusion with human papillomavirues 6b L1

Effective adjuvants are needed to design effective vaccines against Chlamydia trachomatis (Ct). The aim of this study was to observe the immune response stimulated by inoculation of a DNA vaccine encoding a fusion protein comprising multiple Ct major outer membrane protein (MOMP) epitopes and human papillomavirus 6b L1 (HPV 6b L1) as the basis for designing a novel DNA vaccine against genital Chlamydia infections. The recombinant sequence encoding MOMP multi-epitopes was tandemly inserted and engaged downstream of HPV 6b L1 to construct a plasmid vaccine. COS-7 cells were transfected with pcDNA3.1(+)/Ct MOMP 168 encoding the Ct MOMP multi-epitope gene and co-expressed with the nucleic vaccine plasmid pcDNA3.1(+)/HPV 6b L1/Ct MOMP 168, which contains both the HPV 6b L1 and Ct MOMP multi-epitope genes. In addition, BALB/ c mice were inoculated intramuscularly (i.m.) with pcDNA3.1(+)/HPV 6b L1/Ct MOMP 168 or pcDNA3.1(+)/Ct MOMP 168. Serum IgG and secretory IgA (sIgA) in vaginal washes were then measured. The expression of HPV 6b L1/Ct MOMP multi-epitope was confirmed by western blotting, confocal microscopy and RT-PCR. Mice vaccinated with pcDNA3.1(+)/HPV 6b L1/Ct MOMP 168 had significantly higher IgG and sIgA antibody titers than pcDNA3.1(+)/Ct MOMP 16 controls. The results show that genetic fusion of the molecular adjuvant HPV 6b L1 to Ct MOMP 168 significantly increases the antigen-specific antibody response induced by the Ct MOMP 168 DNA vaccine.

Evaluation of efficacy of a new live Salmonella Typhimurium vaccine candidate in a murine model

Efficacy of a new live Salmonella Typhimurium vaccine candidate attenuated by two virulence gene deletions was evaluated in this study. Live form of the vaccine was orally administered and formalin-inactivated form was intramuscularly (IM) administered. 105 female BALB/c mice were used and divided into 5 groups, A to E, containing 21 mice per group. Serum IgG and secretory IgA titers and levels of serum IFN-γ, IL-4, TNF-α, IL-12 of the immunized groups, especially group C (oral prime-oral booster) significantly increased. In addition, all animals in groups C showed no clinical symptoms and survived the virulent challenges, whereas all or some of mice from the other groups died of the challenge. These indicate that the vaccine candidate can be an effective tool for prevention of Salmonella infections by inducing robustly protective immune responses and leading to the production of inflammatory cytokines. Booster immunization, especially via oral administration, is necessary to optimize its protection.

The level of serum secretory IgA of patients with IgA nephropathy is elevated and associated with pathological phenotypes

Mucosal infection associated episodic macroscopic haematuria is observed in many patients with IgA nephropathy (IgAN), however, the mechanism has not been elucidated. Recent study suggested that secretory IgA (SIgA) might play an important role in the pathogenesis of IgAN. The aim of this study is to investigate the level of serum SIgA and the deposition of SIgA in glomeruli in IgAN patients with different pathological phenotypes. The levels of serum SIgA were detected in 57 patients with IgAN and 48 normal controls. The associations between the levels of SIgA and the pathological phenotypes of IgAN as well as clinical parameters were investigated. Frozen renal sections from 34 of the 57 patients without IgM deposition were immunofluorescence stained and examined by confocal microscopy to detect the co-deposition of IgA and secretory component (SC). The association between deposition of SIgA and the level of serum SIgA was analysed. The level of serum SIgA in patients with IgAN was significantly higher than that of normal controls. The level of serum SIgA in patients with focal proliferative sclerosing IgAN (fpsIgAN) was much higher than that in patients with mild mesangial proliferative IgAN (mIgAN) (P<0.001). The level of serum SIgA correlated with the level of serum creatinine (R=0.509, P<0.001), degree of proteinuria (R=0.643, P<0.001) and creatinine clearance (R= -0.454, P=0.002) in patients with IgAN. Significant co-deposition of SC and IgA were found in 11 of the 34 patients. Although the level of serum SIgA in patients with SC deposits was higher than those without SC deposits, the difference was not significant. It was concluded that mesangial IgA, at least partly, was originated from mucosal immune sites. The levels of serum SIgA were significantly increased in patients with IgAN and were closely associated with pathological phenotypes.

Secretory immunoglobulin A (sIgA) deficiency inserum of patients with GALTectomy (appendectomy and tonsillectomy)

Introduction In adult human beings, 80–85% of the immune cells are located in the digestive tract mucosa; hence the importance of the Gut Associated Lymphoid Tissue (GALT) in host defence. We studied the influence of the surgical removal of two important parts of the gut associated with lymphoid tissue (tonsillectomy and appendectomy) on immune parameters. Methods One hundred and sixty patients were enrolled in this study. They were divided into four groups of forty patients each and matched for gender and age: group 1, appendectomized and tonsillectomized; group 2, only appendectomized; group 3, only tonsillectomized; and group 4, control group, neither tonsillectomized nor appendectomized. We analysed in blood: hemogram, protein electrophoresis, lymphocytic populations (T4 cells, T8 cells, NK cells), IgG, IgM, IgA immunoglobulin, and their fractions IgA1, IgA2, and secretory IgA. Results Levels of secretory IgA in serum of patients in group 1 were significantly lower than in the other three groups (1.89 mg/dl, group 1; 2.32 mg/dl, group 2; 2.19 mg/dl, group 3 and 4.97 mg/dl, group 4; p < 0.0001). Also, the values found in the two groups that had undergone only one of the operations were clearly lower than in control patients ( p < 0.0001). In this study, the reduction was sustained for a period of between 3 months and 3 years in appendectomized patients, and more than 20 years in tonsillectomized patients. In summary GALTectomy (appendectomy and tonsillectomy) significantly decreases secretory IgA levels in serum. The decrease is more intense when both operations have been done.

A pathogenic role for secretory IgA in IgA nephropathy

IgA nephropathy (IgAN) is characterized by deposits of IgA in the renal mesangium. It is thought that deposits of IgA mainly involve high molecular weight (HMW) IgA1. However, there is limited information on the exact composition of HMW IgA in these deposits. In this study, we investigated the presence of secretory IgA (SIgA) in human serum and in the glomerular deposits of a patient with IgAN. Furthermore, we analyzed the interaction of SIgA with mesangial cells. With enzyme-linked immunosorbent assay, SIgA concentrations in the serum of IgAN patients and healthy controls were measured. Both patients and controls had circulating SIgA that was restricted to the HMW fractions. Patients tended to have higher levels of SIgA, but this difference was not significant. However, in patients with IgAN, high serum SIgA concentrations were associated with hematuria. Binding of size-fractionated purified serum IgA and SIgA to mesangial cells was investigated with flow cytometry. These studies showed stronger binding of SIgA to primary mesangial cells compared to binding of serum IgA. Importantly, after isolation and elution of glomeruli from a nephrectomized transplanted kidney from a patient with recurrent IgAN, we demonstrated a 120-fold accumulation of SIgA compared to IgA1 in the eluate. In conclusion, we have demonstrated that SIgA strongly binds to human mesangial cells, and is present in significant amounts in serum. Furthermore, we showed that SIgA is accumulated in the glomeruli of an IgAN patient. These data suggest an important role for SIgA in the pathogenesis of IgAN.

Involvement of tonsils in IgA nephropathy

This study was intended to clarify the involvement of tonsils in the pathogenesis of IgA nephropathy. In 62 patients with IgA nephropathy and 20 patients with other renal diseases, their tonsils were stimulated by an ultra short wave. Forty of 62 patients with IgA nephropathy (65%) showed a deterioration of urinary findings after the stimulation compared with six of 20 patients with other renal diseases (30%). Previous episodes of gross hematuria following upper respiratory tract infections existed in 17 of 40 patients (Group A) who showed a deterioration of urinary findings after tonsil stimulation (43%) as against in four of 22 (Group B) without the deterioration (18%). The level of serum secretory IgA was higher in Group A than in Group B. It is suggested that chronic tonsillitis may play an important role in the development of IgA nephropathy. Thirty-six patients received tonsillectomy from 1980–2002. The frequency of gross hematuria at upper respiratory infection decreased in 56% of the patients. The amount of urinary protein decreased in 33% of the patients and RBC counts decreased in 56% of the patients. Eight patients with tonsillectomy were followed up longer than 16 years. Two of them went to hemodialysis and five of them showed no urinary abnormalities at present. The effect of tonsillectomy in the long term was not clarified in this study.

Secretory immunoglobulin A in pancreatic juice and pancreatic tissue of patients with chronic pancreatitis

Background—The predominace of secretory IgA (S-IgA) in intestinal secretions compared with blood is well established, but concentrations of this protein in pancreatic juice and its origin, especially in chronic pancreatitis,...

Secretory IgA anti-HAV in bile of hepatitis A patients

To determine whether IgA with secretory component (secretory IgA) anti-hepatitis A virus (HAV) antibody, is present in the bile of hepatitis A patients. Bile samples from 21 patients with acute hepatitis A: five with acute hepatitis B; five with acute hepatitis C; and five with extrahepatic obstructive jaundice were tested for secretory IpA anti-HAV. Secretory IgA anti-HAV were measured using radioimmunoassay (RIA). The time course of serum secretory IgA anti-HAV in seven patients with acute hepatitis A was also investigated. Secretory IgA anti-HAV in bile juice was detected in 85.7% (18/21) of hepatitis A patients, but was undetected in 15 control cases. The titer was lower in the acute phase and became higher during convalescence. Serum secretory IgA anti-HAV was also detectable, however, only in the acute phase. We have confirmed the presence of secretory IgA anti-HAV in the bile juice of hepatitis A patients which may play an important role in protection against HAV infection through the bile duct or digestive tract.

Development of novel influenza virus vaccines and vectors.

Approaches to improve the efficacy of the current (killed) influenza virus vaccines include the generation of cold-adapted and genetically engineered influenza viruses containing specific attenuating mutations. It is hoped that these genetically altered viruses, in which the hemagglutinin and neuraminidase genes from circulating strains have been incorporated by reassortment, can be used as safe live influenza virus vaccines to induce a long-lasting protective immune response in humans. In addition, genetically engineered influenza viruses may provide a means for expressing foreign antigens. Immunization of mice with recombinant influenza and vaccinia viruses expressing specific antigens of Plasmodium yoelii resulted in a dramatic protective immune response against malaria in this model. Mice immunized with recombinant influenza viruses expressing human immunodeficiency virus (HIV) epitopes generated long-lasting HIV-specific serum antibodies and secretory IgA in the secretory nasal, vaginal, and intestinal mucosa. These results suggest that genetically engineered influenza viruses may be developed for use as live virus vaccines against influenza as well as other diseases.

Mucosal immune response to an HIV C4/V3 peptide following nasal or intestinal immunization of rabbits.

The HIV env-encoded synthetic peptide T1-SP10MN(A) contains immunodominant epitopes of the C4/V3 regions of gp120. The mucosal immunogenicity of this peptide in various vaccine preparations was first tested in rabbits using chronically isolated Thiry-Vella (T-V) ileal loops. Intestinal and serum samples collected from rabbits immunized via T-V loops demonstrated secretory IgA (S-IgA) and IgG anti-T1-SP10MN(A), respectively, when assayed by ELISA. Intranasal delivery of the peptide supplemented with cholera toxin (CT) resulted in serum IgG and S-IgA anti-T1-SP10MN(A) in vaginal and nasal secretions. This study further demonstrates the utility of rabbits as a convenient animal model for HIV vaccine research and the relationship between nasal immunization and vaginal immunity.

Biliary IgA secretion in obstructive jaundice: The effects of endoscopic drainage

Background: Immunoglobulin A is the predominant immunoglobulin in the bile. Data on the effects of biliary obstruction on IgA secretion are few. Methods: The serum and bile IgA levels in patients with common duct stones (n = 27) or with malignant obstructive jaundice (n = 20) were collected by insertion of nasobiliary catheters. Single samples of common duct bile from patients with gallstones (n = 24) were collected as controls. Bile samples collected were measured for total IgA, secretory IgA, and free secretory component levels by sandwich enzyme-linked immunosorbent assays. Results: Bile total IgA, secretory IgA, and free secretory component in the common duct stones group (82.7 ± 11.4 μg/ml, 18.4 ± 1.7 μg/ml, 0.74 ± 0.15 μg/ml) and the malignant obstructive jaundice group (81.6 ± 10.7 μg/ml, 18.2 ± 2.4 μg/ml, 0.57 ± 0.12 μg/ml) were found to be significantly lower than those of the control gallstone patients (104.8 ± 3.4 μg/ml, 33.2 ± 2.9 μg/ml, 1.03 ± 0.12 μg/ml) (P < 0.05). Serum secretory IgA levels in the common duct stones (26.53 ± 1.75 μg/ml) and malignant obstructive jaundice groups (26.03 ± 3.48 μg/ml) were significantly higher than the gallstone group (18.45 ± 4.56 μg/ml). The bile-to-serum concentration ratio of total IgA, secretory IgA, and free secretory component levels rose significantly within 48 hours after relief of obstruction. Conclusions: Biliary obstruction secondary to both calculus or malignancy of the hepatobiliary system causes suppression of bile IgA secretion and elevated serum level of secretory IgA. Bile secretory IgA secretion recovers with endoscopic drainage of the obstructed system. (Gastrointest Endosc 1995;42:439-44.)

Reference interval for serum secretory IgA

Journal Article Reference interval for serum secretory IgA Get access M Negri, M Negri Search for other works by this author on: Oxford Academic Google Scholar A Gheller, A Gheller Search for other works by this author on: Oxford Academic Google Scholar M Zanini, M Zanini Search for other works by this author on: Oxford Academic Google Scholar S Tonni, S Tonni Search for other works by this author on: Oxford Academic Google Scholar M Caputo M Caputo Search for other works by this author on: Oxford Academic Google Scholar Clinical Chemistry, Volume 41, Issue 4, 1 April 1995, Page 634, https://doi.org/10.1093/clinchem/41.4.634a Published: 01 April 1995

Serum secretory IgA and secretory component in patients with non-cirrhotic alcoholic liver diseases

Elevated levels of secretory IgA in serum have been demonstrated in several liver dysfunctions such as hepatic cytolysis and cholestasis. However, these possible alterations at an eary stage of liver diseases have not yet been investigated. We studied a cohort of chronic alcoholic patients without cirrhosis in order to assess the changes in serum secretory IgA and other forms of secretory component, the split product of the polymeric Ig-receptor of epithelial cells. The possible diagnostic value of these measurements in the assessment of alcoholic disease was compared to that of serum gamma-glutamyl transpeptidase activity.Serum levels of secretory IgA and IgM and free secretory component, were quantified by an enzyme-linked immunosorbent assay in 71 patients with chronic alcoholic liver disease without cirrhosis and in 45 healthy controls. Patients were divided into two groups according to the severity of the liver abnormalities. In addition, the reversibility of serum secretory IgA, IgM and free secretory component abnormalities after alcohol withdrawal was evaluated in 15 patients.Serum levels of the three molecular forms of secretory component were significantly higher than those measured in control subjects, both in the whole population of patients and in the two groups of alcoholic patients without cirrhosis. In all groups, serum secretory IgA levels were correlated to free secretory component but not to total IgA levels. Serum secretory IgA levels were as discriminative as gammaglutamyl transferase activity in distinguishing between chronic alcoholic patients without cirrhosis and non-alcoholic subjects. The abnormalities of serum secretory IgA concentrations were reversible after alcohol withdrawal.The results of this study demonstrate that serum secretory IgA and free secretory component levels are significantly increased in patients with chronic alcoholic liver disease, even at a very early stage of the disease, and decrease after alcohol withdrawal. Serum secretory IgA could therefore be used as an additional marker of mild liver abnormalities in chronic alcoholic subjects, and of the effectiveness of alcohol withdrawal. Release of polymeric Ig-receptor into the serum could share a similar physiopathological mechanism with gamma-glutamyl transpeptidase.

Serum Secretory IgA and IgM and Free Secretory Component in IgA Nephropathy

IgA nephropathy (IgAN) is characterized by the presence of IgA and C3 deposits in the mesangium. Mesangial IgA is mostly dimeric IgA1 with a J chain, lacking a secretory component. In view of the recent demonstration of elevated serum levels of secretory component and secretory IgA in liver disease and HIV infection associated with hyper-IgA, we measured the serum secretory component in 50 IgAN patients and 45 controls. Free secretory component and secretory IgA and IgM levels were determined by enzyme-linked immunosorbent assay. Normal or low levels were found patients. These data support previous work suggesting that in IgAN circulating and probably mesangial IgA do not originate from the epithelial compartment of the mucosal immunoglobulins as it is the case in other hyper-IgA diseases.