Molecular size heterogeneity of immunoglobulins in health and disease

Significance of Glomerular Immune Reactivity in Time Zero Biopsies for Allograft Survival Beyond IgA

The quality of a renal transplant can influence the clinical course after transplantation. Glomerular immune reactivity in renal transplants has previously been described, focusing particularly on IgA, and has been shown to disappear in most cases without affecting the outcome. Here, we describe a cohort of time zero biopsies with regard to glomerular immune reactivity and implications for histomorphology and follow-up. 204 Time zero biopsies were analyzed by immunohistochemistry for glomerular immune reactivity. Time zero and 1-year biopsies were evaluated for histomorphological changes, which, together with clinical and follow-up data, were assessed for associations with glomerular immune profiles. Nearly half of the analyzed time zero biopsies showed glomerular immune reactivity with mesangial C3 being the most common (32.9%), followed by IgA (13.7%) and fullhouse patterns (6.9%). Strong C3 deposits (C3high) were only observed in deceased transplants. In the majority of cases immune reactivity was undetectable in follow-up biopsies and had no adverse effect on transplant function in follow-up of 5 years. In kidney pairs transplanted to different recipients a strong concordance of immune profiles in both kidneys was observed. Moreover, an association of male donor sex and deceased donor transplantation with the presence of immune reactivity was observed. In conclusion, glomerular immune reactivity is a very frequent finding in time zero biopsies, which seems to be determined by donor parameters including male sex and deceased donor transplants. It had no adverse impact on transplant function in 5-year follow-up. Glomerular immune reactivity in time zero biopsies, therefore, does not appear to indicate an inferior quality of the transplant.

Dialysis and plasmapheresis for schizophrenia: a systematic review

Increasing evidence suggests that circulating factors and immune dysfunction may contribute to the pathogenesis of schizophrenia. In particular, proinflammatory cytokines, complement and autoantibodies against CNS epitopes have recently been associated with psychosis. Related concepts in previous decades led to several clinical trials of dialysis and plasmapheresis as treatments for schizophrenia. These trials may have relevance for the current understanding of schizophrenia. We aimed to identify whether dialysis or plasmapheresis are beneficial interventions in schizophrenia. We conducted a systematic search in major electronic databases for high-quality studies (double-blinded randomised trials with sham controls) applying either haemodialysis or plasmapheresis as an intervention in patients with schizophrenia, published in English from the start of records until September 2018. We found nine studies meeting inclusion criteria, reporting on 105 patients in total who received either sham or active intervention. One out of eight studies reported a beneficial effect of haemodialysis on schizophrenia, one a detrimental effect and six no effect. The sole trial of plasmapheresis found it to be ineffective. Adverse events were reported in 23% of patients. Studies were at unclear or high risk of bias. It is unlikely that haemodialysis is a beneficial treatment in schizophrenia, although the studies were of small size and could not consider potential subgroups. Plasmapheresis was only addressed by one study and warrants further exploration as a treatment modality in schizophrenia.

Comparative Structural Study of Terminal Ends of Lipoarabinomannan from Mice Infected Lung Tissues and Urine of a Tuberculosis Positive Patient

Mycobacterium tuberculosis lipoarabinomannan (LAM) is a biomarker for active tuberculosis (TB) disease. The presence of LAM in the urine of TB patients, whether HIV positive or negative, has been validated by a gas chromatography/mass spectral method with good specificity (84%) and sensitivity (99%). However, point-of-care (POC) methods to detect TB LAM in urine using immunoassays have poor sensitivity and are limited to only HIV coinfected TB diagnosis. We hypothesized that these disappointing results with the POC methods may be due to the antibodies used in the immunoassays as there could be structural differences between LAM in vivo and LAM in vitro. To address this issue, we infected C3HeB/FeJ mice with M.tb W. Beijing SA161 and purified LAM from the lung. Analysis of these sources of LAM using a panel of existing mAbs revealed differences in epitope patterns. Conventionally, the non-reducing termini of LAM are identified by their release with endoarabinanase. These epitopes correspond to linear tetra-(Ara₄), branched hexa-(Ara₆) arabinofuranosides, and their mannose-capped versions. We discovered two distinct epitopes. In the first case, it was found that the non-reducing termini of LAM from M.tb strain SA161 are highly succinylated, especially when the LAM was isolated from the mouse lungs. In the second case, it was found that Cellulomonas endoarabinanase digestion of LAM from both SA161 and LAM from a TB+ HIV- patient's urine yielded epitopes based on 5 arabinoses as major components and a profound lack of Ara₆. The epitopes based on 5 arabinoses from M.tb SA161 and from the LAM in human urine must result from underlying structural and thus epitope differences. These results suggest approaches to develop specific antibodies for POC tests for LAM in the urine of suspected TB patients.

A matched case-control study comparing features, treatment and outcomes between patients with non-IgM lymphoplasmacytic lymphoma and Waldenström macroglobulinemia

Cases of non-IgM lymphoplasmacytic lymphoma (LPL) are rare. We performed a case-control study comparing features and outcomes of 31 non-IgM LPL cases and 93 Waldenström macroglobulinemia (WM) controls matched by age, sex, and year of diagnosis. Odds of MYD88 mutations were lower (odds ratio (OR) 0.22, p = .05), and median time to treatment was shorter in cases than in controls (4 vs. 32 months; p < .001). Odds of extramedullary disease were higher (OR 4.20, p = .01), while odds of neuropathy (OR 0.22, p = .25), and hyperviscosity (OR 0.26, p = .26) were lower in cases than in controls. Odds of using chemoimmunotherapy were higher (OR 2.62, p = .11) while odds of using proteasome inhibitors (OR 0.35, p = .15) and BTK inhibitors (OR 0.17, p = .21) were lower in cases than in controls. There were no differences in response and overall survival (OS) between cases and controls. Despite clinicopathological differences, response, and survival outcomes are similar between non-IgM LPL cases and WM controls.

Proteomic Characterization of Immunoglobulin Content in Dermal Interstitial Fluid

Microneedles have been demonstrated to be a minimally invasive technique for sampling dermal interstitial fluid (ISF). Shotgun quantitative proteomics has already identified hundreds of proteins in ISF and quantitatively compared the proteome to matching serum and plasma. Interstitial fluid was determined to be a viable minimally invasive alternative to blood-derived fluids. In this communication, we re-examined the proteomic data from previous work to determine the diversity of immunoglobulins present compared with serum and plasma. Similar to our previous findings regarding the proteomic content across fluid types, ISF had a similar composition of IgG, IgA, IgD, and IgE antibodies as plasma or serum and lower quantities of IgM, which reflects the relative concentrations of dermal tissue T-cell and B-cell populations, indicating that the Ig's were likely locally derived. This work has significant implications for the utility of measuring Ig's in ISF for the clinical diagnosis of immunological diseases and skin infections. Data are available via ProteomeXchange with identifier PXD012658.

Raman spectroscopic screening of high and low molecular weight fractions of human serum

This study explores the suitability of Raman spectroscopy as a bioanalytical tool, when coupled with ultra-filtration and multivariate analysis, to detect imbalances in both high molecular weight and low molecular weight fractions of the same samples of human patient serum, in the native liquid form.

Lipoarabinomannan in urine during tuberculosis treatment: association with host and pathogen factors and mycobacteriuria

BACKGROUND

Detection of lipoarabinomannan (LAM), a Mycobacterium tuberculosis (Mtb) cell wall antigen, is a potentially attractive diagnostic. However, the LAM-ELISA assay has demonstrated variable sensitivity in diagnosing TB in diverse clinical populations. We therefore explored pathogen and host factors potentially impacting LAM detection.

METHODS

LAM-ELISA assay testing, sputum smear and culture status, HIV status, CD4 cell count, proteinuria and TB outcomes were prospectively determined in adults diagnosed with TB and commencing TB treatment at a South African township TB clinic. Sputum TB isolates were characterised by IS61110-based restriction fragment length polymorphism (RFLP) and urines were tested for mycobacteriuria by Xpert® MTB/RIF assay.

RESULTS

32/199 (16.1%) of patients tested LAM-ELISA positive. Median optical density and proportion testing LAM positive remained unchanged during 2 weeks of treatment and then declined over 24 weeks. LAM was associated with positive sputum smear and culture status, HIV infection and low CD4 cell counts but not proteinuria, RFLP strain or TB treatment outcome. The sensitivity of LAM for TB in HIV-infected patients with CD4 counts of ≥ 200, 100-199, 50-99, and < 50 cells/μl, was 15.2%, 32%, 42.9%, and 69.2% respectively. Mycobacteriuria was found in 15/32 (46.9%) of LAM positive patients and in none of the LAM negative controls.

CONCLUSIONS

Urinary LAM was related to host immune factors, was unrelated to Mtb strain and declined steadily after an initial 2 weeks of TB treatment. The strong association of urine LAM with mycobacteriuria is a new finding, indicating frequent TB involvement of the renal tract in advanced HIV infection.

A CMOS Electrochemical Impedance Spectroscopy (EIS) Biosensor Array

In this paper, we present a fully integrated biosensor 10 × 10 array in a standard complementary metal-oxide semiconducor process, which takes advantage of electrochemical impedance spectroscopy (EIS). We also show that this system is able to detect various biological analytes, such as DNA and proteins, in real time and without the need for molecular labels. In each pixel of this array, we implement a biocompatible Au electrode transducer and embedded sensor circuitry which takes advantage of the coherent detector to measure the impedance of the associated electrode-electrolyte interface. This chip is capable of concurrently measuring admittance values as small as 10(-8) Ω(-1) within the array with the detection dynamic range of more than 90 dB in the frequency range of 10 Hz-50 MHz.

Irreversible aggregation of the Fc fragment derived from polymeric but not monomeric serum IgA1—Implications in IgA-mediated disease

IgA is by far the most abundant immunoglobulin in humans. It is found in serum and in secretions (SIgA). Unlike any other class of immunoglobulin, each form of IgA occurs naturally in different polymerisation states. In serum, the predominant form of IgA is IgA1 of which around 90% is monomeric and 10% is dimeric or polymeric. The proportion of dimeric/polymeric IgA increases in a number of important diseases, such as IgA nephropathy and in chronic liver disease. In both, there is evidence that further aggregation of dimeric/polymeric IgA is the cause of the characteristic tissue deposition. To investigate the effect of role of IgA polymerisation on the structure and function of IgA, we purified different molecular forms of IgA1 from myeloma serum (monomer, dimer and trimer) and SIgA1 from colostrum. Structural features of these different IgA1 forms were examined following proteolysis using Neisseria gonorrhoeae IgA1 type 2 protease and Streptococcus pneumoniae IgA1 protease. These IgA1 proteases cleave IgA1 at the hinge region and produce Fcalpha and Fab fragments. Western blot analysis demonstrated that the Fcalpha fragments of serum dimeric and trimeric but not monomeric IgA1 aggregated to form multimers resistant to disruption in SDS-PAGE under non-reducing conditions. Size exclusion chromatography under native conditions of cleaved serum dimeric IgA1 demonstrated that aggregation occurs because of structural changes in the IgA per se and was not an effect of the SDS-PAGE system. In the same assay, SIgA1 (dimeric) did not aggregate after digestion. The results suggest an important, previously unrecognised, property of dimeric/polymeric serum IgA1, which might explain its propensity to aggregate and deposit in tissues.

Purification, Properties and Extended Solution Structure of the Complex Formed between Human Immunoglobulin A1 and Human Serum Albumin by Scattering and Ultracentrifugation

Immunoglobulin A (IgA) is unique amongst antibodies in being able to form polymeric structures that may possess important functions in the pathology of specific diseases. IgA also forms complexes with other plasma proteins, the IgA1-human serum albumin (HSA) complex (IgA1-HSA) being typical. We have purified this complex using a novel two-step purification based on thiophilic chromatography and gel filtration, and characterised this. HSA is linked covalently to the tailpiece of IgA1 by a disulphide bond between Cys471 in IgA1 and Cys34 in HSA. IgA1-HSA binds to IgA receptors on neutrophils and monocytes, and elicits a respiratory burst that is comparable in magnitude to that of monomeric IgA1. The solution arrangement of IgA1-HSA was identified by X-ray scattering and ultracentrifugation. The radius of gyration R(G) of 7.5(+/-0.3) nm showed that IgA1-HSA is more extended in solution than IgA1 (R(G) of 6.1-6.2 nm). Its distance distribution function P(r) showed two peaks that indicated a well-separated solution structure similar to that for IgA1, and a maximum dimension of 25 nm, which is greater than that of 21 nm for IgA1. Sedimentation equilibrium showed that the IgA1:HSA stoichiometry is 1:1. Sedimentation velocity resulted in a sedimentation coefficient of 6.4S and a frictional ratio of 1.87, which is greater than that of 1.56 for IgA1. The constrained modelling of the IgA1-HSA structure using known structures for IgA1 and HSA generated 2432 conformationally randomised models of which 52 gave good scattering fits. The HSA structure was located at the base of the Fc fragment in IgA1 in an extended arrangement. Such a structure accounts for the functional activity of IgA1-HSA, and supports our previous modelling analysis of the IgA1 solution structure. The IgA1-HSA complex may suggest the potential for creating a new class of targeted therapeutic reagents based on the coupling of IgA1 to carrier proteins.

Structural and functional consequences of cleavage of human secretory and human serum immunoglobulin A1 by proteinases from Proteus mirabilis and Neisseria meningitidis

The cleavage of human serum monomeric immunoglobulin A1 (IgA1) and human secretory IgA1 (S-IgA1) by IgA1 proteinase of Neisseria meningitidis and cleavage by the proteinase from Proteus mirabilis have been compared. For serum IgA1, both proteinases cleaved only the alpha chain. N. meningitidis proteinase cleaved only in the hinge. P. mirabilis proteinase sequentially removed the tailpiece, the CH3 domain, and the CH2 domain. The cleavage of S-IgA1 by N. meningitidis proteinase occurred only in the hinge and was as rapid as that of serum IgA1. P. mirabilis proteinase predominantly cleaved the secretory component (SC) of S-IgA1. The SC of S-IgA1, whether cleaved or not, appeared to protect the alpha1 chain. Purified Fc fragment derived from the cleavage of serum IgA1 by N. meningitidis proteinase stimulated a respiratory burst in neutrophils through Fcalpha receptors, whereas the (Fcalpha1)(2)-SC fragment from digested S-IgA1 did not. The loss of the tailpiece from serum IgA1 treated with P. mirabilis proteinase had little effect, but the loss of the CH3 domain was concurrent with a rapid loss in the ability to bind to Fcalpha receptors. S-IgA1 treated with P. mirabilis proteinase under the same conditions retained the ability to bind to Fcalpha receptors. The results are consistent with the Fcalpha receptor binding site being at the CH2-CH3 interface. These data shed further light on the structure of S-IgA1 and indicate that the binding site for the Fcalpha receptor in S-IgA is protected by SC, thus prolonging its ability to activate phagocytic cells at the mucosal surface.

Autoantibodies in endometriosis sera recognize a Thomsen-Friedenreich-like carbohydrate antigen

Autoantibody responses to endometrial antigens are a common feature of endometriosis. Antibody responses to a number of serum and tissue antigens such as alpha(2)-Heremans Schmidt glycoprotein (alpha(2)-HSG), transferrin, and carbonic anhydrase have been identified. The nature of the epitopes recognized on these proteins has not been determined. In this study we show that the serum antibody response to alpha(2)-HSG and carbonic anhydrase is against a common carbohydrate epitope which is also expressed on bovine fetuin. Removal of carbohydrate moieties from these antigens resulted in loss of antibody binding. Antibody reactivity with alpha(2)-HSG, fetuin and other antigens was removed by binding with the lectin jacalin. Jacalin specifically binds the Thomsen-Friedenreich antigen (Galbeta1-3GalNAc). Demonstrating that the autoantibodies also reacted with other Thomsen-Friedenreich antigen-bearing proteins, serum IgA1 and haemopexin confirmed an association with this epitope. These antigens have not been previously described as autoantigens in endometriosis and are of interest since they raise the possibility that this autoimmune response may either play a direct role in the disease process or reflect an abnormality of glycosylation in endometriosis. These results may also prove useful in the development of a serum diagnostic test for endometriosis.

Studies on IgA class circulatory red cell antibodies--II. Properties of IgA class anti-A,anti-B

The properties of IgA class red cell alloantibodies were determined using an anti-A,anti-B preparation confirmed to be free from IgG and IgM. The following characteristics were found: a thermal optimum of 37 degrees C; saline agglutination enhanced by anti-human IgA; activity substantially unchanged after 1 year's storage at 4 degrees C, but reduced by papain and destroyed by pepsin and by reduction and alkylation; neutralization by AB blood group substance; an inability to activate complement; and a distinctive pattern of apparent molecular sizes (reflecting dimeric and monomeric forms and complexes with serum proteins) which was significantly altered by the action of enzymes and by reduction and alkylation.

Introduction of high molecular weight (IgG) proteins into receptor coupled, permeabilized smooth muscle

The permeability to high molecular weight (IgG, 150 kD) proteins of the plasma membrane of receptor-coupled smooth muscles permeabilized with beta-escin was determined using confocal microscopy of immunofluorescent tracers and measurement of lactate dehydrogenase (LDH, 135-140 kD) leakage. Permeabilized strips of rabbit portal vein and guinea pig ileum were incubated in a relaxing solution containing mouse anti-smooth muscle alpha-actin antibody and immunostained with F(ab')2 labeled with tetramethyl rhodamine isothiocyanate. Confocal light microscopy of Triton X-100 and beta-escin permeabilized cells showed homogeneous staining of the cytoplasm, whereas in alpha-toxin treated and intact preparations only damaged cells at the edges of the strips were stained. Both the Ca(2+)-sensitizing effect of phenylephrine, in rabbit portal vein, and Ca2+ release by carbachol in guinea pig ileum, were retained after permeabilization and the treatment with the primary antibody. During the 30 min permeabilization, 38%, and within the next 75 min an additional approximately 30%, of the total LDH leaked out from the beta-escin-treated group, but not from the alpha-toxin-treated group (3.2%). The responsiveness to agonist and maximum contractility was improved if the preparations were incubated during the introduction of proteins at 4 degrees C, rather than 24 degrees C. Ca(2+)-independent myosin light chain kinase (61 kD) contracted the permeabilized portal vein in the absence of free Ca2+ (pCa < 8). In conclusion, permeabilization with beta-escin allows the transmembrane passage of 150 kD proteins under our experimental conditions that also retain receptor-coupled signal transduction.

Low molecular weight IgM in the sera of patients with chronic lymphocytic leukemia

With the use of 2 independent techniques, circulating monomeric and oligomeric IgM were detected in the majority of 29 patients with chronic lymphocytic leukemia (CLL). In contrast it was detected only in trace quantities in a minority of healthy subjects. In the CLL group no significant correlation was observed between monomeric IgM and the total serum IgM level or the absolute lymphocyte count. Mitogen stimulated peripheral blood mononuclear cells from CLL patients were observed to secrete monomeric and oligomeric IgM in-vitro. Experiments manipulating the microenvironment of an IgM secreting cell line revealed that the addition of low concentrations of the reducing reagent 2-mercaptoethanol to the culture medium would enhance the proportions of monomeric IgM in the culture supernatant and the cellular cytoplasmic lysate. However the same concentrations would not directly reduce the secreted IgM. We conclude that the secretion of incompletely assembled IgM is commonly found in CLL and suggests an intrinsic defect(s) in the mechanisms involved in the polymerization of the monomeric units into the pentameric molecule.