Progress in Molecular and Genetic Studies of IgA Nephropathy

Several new findings emerged recently from biochemical, genetic, and molecular studies of patients with IgA nephropathy. It appears that immunoglobulin A1-secreting cells of IgA nephropathy patients produce increased amounts of aberrantly glycosylated IgA1 in which the O-linked glycans in the hinge region are deficient in the content of galactose. The galactose-deficient IgA1 in the circulation is recognized by naturally occurring antibodies with anti-glycan specificity, and immune complexes are formed. These circulating immune complexes escape hepatic degradation and eventually are deposited in the kidney mesangium. Resident mesangial cells bind the IgA-containing immune complexes with the involvement of a novel IgA receptor and become activated. A familial form of IgA nephropathy has been linked to chromosome 6q22-23. Recent progress in molecular analyses of IgA nephropathy thus defines this disease as an autoimmune process with a novel IgA mesangial receptor and certain genetically determined traits.     

IgA肾病患者血清IgA1对人肾小球系膜细胞转化生长因子β1/Smads信号通路的影响

目的 研究IgA肾病(IgAN)患者血清IgA1对人肾小球系膜细胞(HMC)转化生长因子β1(TGF-β1)、磷酸化Smad3(p-Smad3)和纤连蛋白(FN)的刺激作用,探讨IgA1对TGF-β1/Smads信号通路的影响.方法 体外培养HMC,分5组.即健康对照组、健康人IgA1(NIgA1)刺激组、健康人聚合IgA1(aNIgA1)刺激组、IgAN患者IgA1(PIgA1)刺激组和IgAN患者聚合IgA1(aPIgA1)刺激组.RT-PCR检测各组细胞TGF-β1、p-Smad3和FNmRNA的表达.Western免疫印迹检测HMC p-Smad3蛋白水平.ELISA检测HMC培养上清液中TGF-β1、FN蛋白水平.结果 PIgA1和aPIgA1能显著上调TGF-β1,P-Smad3、FN mRNA和蛋白的表达(P<0.05).aPIgA1上调三者mRNA表达的能力分别为PIgA1的1.5倍、1.3倍和1.5倍(均P<0.05).aPIgA1上调TGF-β1和p-Smad3蛋白表达的能力分别为PIgA1的2.1倍和1.6倍(均P<0.01).在aPIgA1刺激不同时间,TGF-β1和p-Smad3 mRNA表达于12 h达高峰(0.866±0.055和0.891±0.251),于24h回到基线水平.FNmRNA表达于24 h达高峰(0.968±0.031).TGF-β1和p-Smad3蛋白表达逐渐升高,TGF-β1于12 h达高峰[(246.960±1.270)ng/L],p-Smad3于6 h达高峰(0.490±0.046)后开始下降.FN蛋白表达逐渐升高,24 h达高峰[(1.804±0.038)mg/L](均P<0.01).结论 PIgA1和aPIgA1能显著上调HMC TGF-β1、p-smad3、和FNmRNA表达和蛋白水平.且aPIgA1的作用强于PIgA1,提示IgAN患者血清的IgA1,主要是aIgA1可通过TGF-β1/Smads信号通路在IgAN进展中起作用.     

IgA1 is the major immunoglobulin component of immune complexes in the acquired immune deficiency syndrome

Compared to a panel of healthy controls, sera from 13 of 23 (57%) patients with the acquired immune deficiency syndrome (AIDS) were shown to have elevated levels of circulating immune complexes (CIC) containing IgA. Levels of IgG-containing CIC were increased in seven patients (30%); no patients had elevated levels of IgM-containing CIC. Additional experiments showed that in all instances in which IgG CIC were demonstrable, IgA was also present; however, IgA CIC could be found that did not contain IgG. The IgA in the CIC was restricted to the IgA1 subclass. These data suggest selective abnormalities of IgA regulation in AIDS and raise questions as to the role in this disease of the immunoglobulin isotype usually thought to possess different protective mechanisms from those attributed to other isotypes.     

Host—Pathogen Interactions in the Immunopathogenesis of Lyme Disease

The immunopathogenesis of Lyme disease is complicated and requires a thorough understanding of the interaction among the causative organism, Borrelia burgdorferi, its tick vector, and its mammalian hosts. In vitro, animal and human studies have shown that the organism is capable of adapting to and utilizing elements from its environment to establish infection and persist despite a inducing a strong immune response. Indeed, the immune response may be responsible for many of the symptoms associated with Lyme disease. It appears that humoral immunity plays the greatest role in clearance of the organism. Cytokines released by Th 1 or Th 2 subsets of CD4+ cells have been shown to play an important role in determining outcome of the disease in animal models possibly through their effects on immuno-globulin class switching. In the small percentage of patients who have treatment resistant chronic Lyme disease, autoimmune mechanisms may play a role in persistant disease.     

The major circulating immunosuppressive activity in American visceral leishmaniasis patients is associated with a high-molecular weight fraction and is not mediated by IgG, IgG immune complexes or lipoproteins

Opportunistic infections, due to disease-related immunosuppression, constitute the major cause of death in American visceral leishmaniasis (AVL). Sera from these patients (AVL sera) non-specifically inhibit the in vitro proliferative response of normal human lymphocytes to lectins or antigens. In the present work, the mediation of this inhibition by IgG, immune complexes and low- or very low-density lipoproteins was studied. AVL serum fractions containing proteins with the molecular weight of IgG, and IgG, purified from AVL sera by anion exchange chromatography, did not suppress the lymphoproliferation. Most of the suppressive activity of AVL sera was associated with a fraction containing molecules with molecular weights above 430 kDa. This would be compatible with it being due to immune complexes and/or lipoproteins, and not to soluble IL-2 receptors as reported previously. However, neither of the two possibilities seem to be the case, as (1) depletion of immune complexes by protein-A followed by protein-G chromatographies did not affect the serum suppressive activity, (2) no correlation between immune complex contents and suppressive activities in individual sera was observed, and (3) plasma lipoproteins (VLDL and LDL), purified from AVL patients and from healthy individuals, had the same degree of immunosuppressive activity.     

Immunoglobulin A nephropathy associated with Plasmodium falciparum malaria

Glomerulonephritis occurs as a rare form of renal manifestation in Plasmodium falciparum malaria. Herein, we report a case of falciparum malaria-associated IgA nephropathy for the first time. A 49-yr old male who had been to East Africa was diagnosed with Plasmodium falciparum malaria. Microhematuria and proteinuria along with acute kidney injury developed during the course of the disease. Kidney biopsy showed mesangial proliferation and IgA deposits with tubulointerstitial inflammation. Laboratory tests after recovery from malaria showed disappearance of urinary abnormalities and normalization of kidney function. Our findings suggest that malaria infection might be associated with IgA nephropathy.     

Synergistic platelet activation by aggregates of IgG and the phospholipid platelet-activating factor 1-O-alkyl-2-acetyl-SN-glycero-3-phosphorylcholine

Immune complexes and 1-O-alkyl-2-acetyl-SN-glycero-3-phosphorylcholine (AGEPC) are potent platelet-activating factors which interact with distinct receptors on human platelets. The mechanisms of platelet activation by these two stimuli were investigated by examining the effects of AGEPC on human platelets which had been preexposed to IgG aggregates (IgG-Agg). AGEPC and IgG-Agg in combination activated platelet aggregation synergistically, whereas release of the granular constituent serotonin was not increased. Synergy was maximal within 1 min of exposure of platelets to IgG-Agg and persisted for 5 to 10 min after exposure to IgG-Agg. Synergy was observed at concentrations of IgG-Agg which release platelet granular constituents with minimal aggregation. Monomeric IgG, which did not activate platelets, did not augment the platelet response to AGEPC. Platelet activation by AGEPC is enhanced by both the granular constituent adenosine diphosphate (ADP) and by arachidonic acid, suggesting that one or both agents may contribute to synergy between AGEPC and IgG-Agg. Indomethacin inhibited granule release by IgG-Agg and enhancement of AGEPC-induced platelet aggregation by IgG-Agg. The ADP scavengers creatine phosphate/creatine phosphokinase also blocked synergistic platelet activation. These data suggest that IgG-Agg releases platelet granule ADP by a cyclooxygenase-dependent mechanism and the released ADP, in combination with AGEPC, activates platelets synergistically.     

Immunopathogenesis of Ascaridia galli infection in layer chicken

Gastro-intestinal nematode infections in mammals are associated with local T lymphocyte infiltrations, Th2 cytokine induction, and alterations in epithelial cell secretion and absorption. This study demonstrates that Ascaridia (A.) galli infection in chicken also elicits local gut-associated immune reactions and changes in the intestinal electrogenic nutrient transport. In A. galli-infected birds we observed infiltrations of different T cell populations in the intestinal lamina propria and accumulation of CD4+ lymphocytes in the epithelium. The Th2 cytokines IL-4 and IL-13 dominated the intestinal immune reactions following A. galli infection. A. galli-specific systemic IgY antibodies were detected after two weeks post infection, and did only poorly correlate with detected worm numbers. Electrogenic transport of alanin and glucose was impaired in A. galli-infected chicken. Our data provide circumstantial evidence that local immune responses and electro-physiological intestinal functions may be connected and contribute to the elimination of worm infection.     

Human rotavirus specific T cells: quantification by ELISPOT and expression of homing receptors on CD4+ T cells

Using an intracellular cytokine assay, we recently showed that the frequencies of rotavirus (RV)-specific CD4(+) and CD8(+) T cells secreting INFgamma, circulating in RV infected and healthy adults, are very low compared to the frequencies of circulating cytomegalovirus (CMV) reactive T cells in comparable individuals. In children with acute RV infection, these T cells were barely or not detectable. In the present study, an ELISPOT assay enabled detection of circulating RV-specific INFgamma-secreting cells in children with RV diarrhea but not in children with non-RV diarrhea without evidence of a previous RV infection. Using microbead-enriched CD4(+) and CD8(+) T cell subsets, IFNgamma-secreting RV-specific CD8(+) but not CD4(+) T cells were detected in recently infected children. Using the same approach, both CD4(+) and CD8(+) RV-specific T cells were detected in healthy adults. Furthermore, stimulation of purified subsets of PBMC that express lymphocyte homing receptors demonstrated that RV-specific INFgamma-secreting CD4(+) T cells from adult volunteers preferentially express the intestinal homing receptor alpha4beta7, but not the peripheral lymph node homing receptor L-selectin. In contrast, CMV-specific INFgamma-secreting CD4(+) T cells preferentially express L-selectin but not alpha4beta7. These results suggest that the expression of homing receptors on virus-specific T cells depends on the organ where these cells were originally stimulated and that their capacity to secrete INFgamma is independent of the expression of these homing receptors.     

Induction of unresponsiveness against IgA in IgA-deficient patients on subcutaneous immunoglobulin infusion therapy

Patients with IgA deficiency often demonstrate circulating antibodies against IgA, which have been suggested to be associated with transfusion reactions. Sera from three patients with common variable immunodeficiency (CVID) and one with a selective IgA deficiency with anti-IgA antibodies receiving subcutaneous gammaglobulin replacement therapy were analysed for serum levels of IgG, IgA and anti-IgA before and during a treatment period of 4–7 years. Treatment with gammaglobulin preparations containing significant amounts of IgA (< 5 mg/ml) resulted in a decrease or disappearance of the anti-IgA antibodies. Analysis of serum fractions, however, revealed anti-IgA activity in the complex-containing fractions. In vitro experiments gave similar results with a shift of anti-IgA activity from the monomeric to the complex-containing fractions (that could not be detected in whole serum). When the patients were subsequently switched to treatment with a preparation containing less IgA (< 80 μg/ml) or made an interruption in the treatment schedule, the anti-IgA antibodies reappeared. Importantly, however, one of the patients lost his anti-IgA activity during a 3-month period on the preparation containing the higher IgA levels, and these antibodies did not reappear after switching to the low IgA-containing preparation. After 5 years on this preparation, anti-IgA can still not be detected, suggesting induction of unresponsiveness.     

Etiology of IgA nephropathy syndrome

Since Berger's original paper on mesangial IgA-IgG deposition with hematuria, there have been a number of clinical and pathological studies regarding IgA immune complexes, the mechanisms of glomerular IgA deposition leading to glomerular injury and animal models of IgA nephropathy. During the last quarter of this century, glomerular changes such as IgA nephropathy have also been observed in cases associated with other diseases, such as systemic lupus erythematosus, Schoenlein-Henoch purpura, liver cirrhosis and chronic inflammatory diseases of the lung. This evidence supports the idea of an IgA nephropathy syndrome. On the other hand, IgA is thought to be an important humoral factor at the mucosal immune system and appears to have an antibody function against various etiologic candidates of extrinsic or intrinsic substances at the mucosal and systemic immune system. Glomerular IgA deposition in IgA nephropathy syndrome is thought to result from elevated levels of circulating immune complexes or aggregated IgA due to an overproduction of polymeric IgA as antibodies in the serum and due to the clearance impairment of IgA immune complexes in the hepatic and splenic phagocytic system. The glomerular IgA subclass is not one-sided, but should be evaluated in comparison with the age of patients at renal biopsy; this indicates the approximate age of onset. Cirrhotic IgA glomerulonephritis is not related to Hepatitis B or C virus infection, but to the pathophysiologic condition of liver cirrhosis. Various etiologic candidates such as viral, microbial, dietary antigens or auto-antigens have been listed and experimental models of IgA nephropathy syndrome have provided some clues in understanding the etiology of primary IgA nephropathy. However much still remains to be clarified and some specific epitopes common among these etiologic candidates will have to be identified.     

Secretion of suppressor factors by mouse lymphocytes on contact with syngeneic and xenogeneic red cells

During incubation of spleen cells of immune micein vitro with syngeneic and xenogeneic red cells a factor (or factors) with immunosuppressive activity is secreted into the medium. Secretion of the suppressor factor by spleen cells of nonimmune mice takes place only on contact with xenogenic red cells.Department of Immunology, Scientific-Research Center Attached to the N. I. Pirogov Second Moscow Medical Institute. (Presented by Academician of the Academy of Medical Sciences of the USSR Yu. M. Lopukhin.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 83, No. 3, pp. 308–310, March, 1977.     

Individual variations of the immune response in BALB/c mice

The nature and the causes of variations of the immune response to thyroid hormones are analyzed in BALB/c mice. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 119, N ^o 1, pp. 80–82, January, 1995 (Presented by Yu. A. Romanov, Member of the Russian Academy of Medical Sciences)     

Inhibitory effect of C-reactive protein on streptolysin O-mediated hemolytic activity. Comparison of conformational variants

It is shown that C-reactive protein binds to streptolysin O, an exotoxin of hemolytic streptococcus, and neutralizes its hemolytic activity. Incubation of C-reactive protein with the working dose of streptolysin O for 15–20 min at 37°C abolished the hemolysis of subsequently added erythrocytes. The concentration of C-reactive protein that reduced hemolysis by 50% was on average equal to 2.28±0.19 μg/ml. C-reactive protein antihemolytic activity was not affected by blocking of its phosphorylcholine-specific sites with free phosphorylcholine, but decreased as a result of blocking with pneumococcal C-polysaccharide and, particularly, with L-α-phosphatidylcholine. This indicates a hydrophobic nature of C-reactive protein-streptolysin O interaction. C-reactive protein subunits retained antihemolytic activity, while the aggregated C-reactive protein lost part of it. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 119, N ^o 5 pp. 506–509, May, 1995 Presented by A. A. Totolyan, Member of the Russian Academy of Medical Sciences     

Inhibition of Natural Killer Cell Activity by Antigen-Antibody Complexes

The natural killer (NK) cell activity of human peripheral blood mononuclear cells was found to be inhibited by precipitated tetanus toxoid anti-tetanus toxoid complexes (Te/aTe) as well as soluble Te/aTe. Preincubation of the immune complexes with protein A decreased the inhibition of NK cell activity. When mononuclear cells were preincubated with interferon (IF) or interleukin 2 (Il-2) before incubation with Te/aTe, the immune complex-induced inhibition was decreased, while IF or Il-2 added after incubation with the immune complexes had no effect. Using NK cell-enriched suspensions in a single cell agarose assay, the immune complexes were shown to inhibit NK cell activity by inhibiting the formation of effector/target cell conjugates.     

Induction of IgA against Haemophilus parainfluenzae Antigens in Tonsillar Mononuclear Cells from Patients with IgA Nephropathy

Much evidence suggests that IgA production in vivo and in vitro is enhanced in patients with IgA nephropathy (IgAN). We have demonstrated glomerular deposition of the outer membranes of Haemophilus parainfluenzae (HP) antigens (OMHP) and the presence of HP-specific IgA in the serum of patients with IgAN. In this study, we investigated the production of IgA and several cytokines by tonsillar mononuclear cells (TMC) from IgAN patients induced by stimulation with OMHP. The spontaneous production of total IgA and TGF-β by TMC from IgAN patients was higher than that by TMC from patients with chronic tonsillitis (CT) (P < 0.05). Stimulation with OMHP in vitro enhanced the production of HP-specific IgA by TMC from IgAN patients (P < 0.01), but not by TMC from CT patients. OMHP stimulation also enhanced the production of TGF-β and IL-10 by TMC from IgAN patients (P < 0.001). These results suggest that the infection of HP in the tonsil may be involved in the etiology of IgAN.     

Immunological reactivity under conditions of prolonged exposure to ozone

Immune status of 158 workers exposed to ozone in a maximal permissible concentrations (0.1 mg/ml) for a long time was evaluated using a turbidimetric method. A tendency to decrease in IgA concentration in subjects with longer service was detected. The ranges of IgM and IgG levels were determined, which probably reflect individual differences. The concentration of circulating immune complexes in the blood was increased. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 128, No. 10, pp. 422–424, October, 1999     

Immunological aspects of alisat in patients with diabetes mellitus

The effect of long-term (12 months) therapy with the garlic-containing preparation. Alisat on some parameters of immunity is studied in 52 patients with noninsulin-dependent diabetes mellitus (type II). It was found that Alisat increases natural resistance in the beginning of therapy and induces no remote immunopathological responses. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 124, No. 11, pp. 595–597, November, 1997