Dot-immunobinding assay as an accurate and versatile technique for the quantification of human IgG subclasses

IgG2 Deficiency in Young Children Treated with Continuous Ambulatory Peritoneal Dialysis (CAPD)

In most series of children treated with continuous ambulatory peritoneal dialysis (CAPO), the incidence of peritonitis is higher than in adults. This phenomenon has been insufficiently explained. In the serum of 12 young children treated with CAPO, the serum immunoglobulins IgA, IgM, and IgG, as well as the IgG subclasses, were evaluated. In 11 of them, IgG2 was not detectable. Total IgG was also slightly decreased in these patients. In control groups, consisting of children before CAPO was started, children treated with hemodialysis, and adult CAPO patients, no clear abnormalities were found. It is concluded that in young patients peritoneal dialysis causes IgG loss leading to IgG2 deficiency.

Immunoglobulins in children with epilepsy: the Dutch Study of Epilepsy in Childhood

In an unselected cohort of 282 children, serum immunoglobulin (Ig) concentrations were determined shortly after the first presentation with one or more unprovoked epileptic seizures and before the start of treatment with anti-epileptic drugs (AEDs), and after 9-18 months of AEDs use. At intake, IgA, IgG1, IgG2 and IgG4 concentrations were significantly higher than published reference values in healthy age-matched controls. In a subset of 127 children, Ig levels at intake were compared with those after AEDs use for 9-18 months. IgA and IgG4 levels had decreased significantly to normal concentrations, but IgG1 and IgG3 levels increased significantly. To determine the influence of AEDs, Ig levels in children who used carbamazepine or valproic acid monotherapy were analysed separately. The use of carbamazepine was associated with a significant decrease of IgA and IgG4 levels, and the use of valproic acid with a significant decrease of IgA and increase of IgG1 levels. In conclusion, humoral immunity is already altered in children shortly after the first presentation with epileptic seizures. Whether this is the consequence of an exogenous event, and to what extent this is related to an interaction of the central nervous system and the immune system, remains to be evaluated. Treatment with AEDs, such as carbamazepine and valproic acid, is associated with significant changes of Ig (sub)class concentrations.

Frequency of clonal dominance in the specific antibody response to DNP-HSA in CBA and C57BL mice reflects their susceptibility to age-associated development of monoclonal gammopathies

The effects of age, genetic background, and neonatal thymectomy on the levels and the heterogeneity of the specific antibody response were investigated in an experimental mouse model. Both intact and neonatally thymectomized (NTx) C57BL/KaLwRij (C57BL) and CBA/BrARij (CBA) mice were immunized at the age of 3 ("young") or 22 months ("old"). Highly sensitive antigen-specific immunoblotting techniques (ABL), in combination with agar-electrophoresis and isoelectric focusing (IEF), were used to investigate total specific antibody levels, the number of responding antigen-specific clonotypes, and the dominance of responding B cell clones in the antibody response against dinitrophenylated human serum albumin. After immunization, the specific antibody levels progressively increased in all experimental groups with the exception of old C57BL mice. All mice responded with a specific polyclonal heterogeneous response. In addition, some mice showed a clonal dominance of antibody-producing cells, as is reflected in the appearance of distinct homogeneous antibody components (H-Ab) in the sera. This clonal dominance was scarce in CBA mice but frequent in C57BL mice. Age at time of immunization and NTx had little if any additive effect on the incidence of H-Ab in either mouse strain. All dominant clones showed different electrophoretic mobility, indicating the proliferation of various clonotypes and not a strain-specific dominance of one clone. In old C57BL mice the specific antibody response was more restricted in heterogeneity, as is illustrated by more visible spectrotype bands in IEF and subsequent ABL. Hence, in old C57BL mice smaller amounts of specific antibodies were produced by fewer clones. Still, the incidence of H-Ab in this group was the same as that in the group of young C57BL mice. This indicates that at old age the responding B cell clones are more prone to becoming clonally dominant in C57BL mice. This tendency correlates with the high incidence of spontaneously developing monoclonal gammopathies in aging C57BL mice.

Manipulating blood T cells and B cells from squirrel monkeys: some technical considerations

The squirrel monkey Saimiri sciureus is an experimental host for a range of human pathogens, and for the assessment of vaccine candidate antigens and vaccine strategies. This experimental host is thus particularly suitable for the follow-up of humoral responses. To understand some of the mechanisms that underlie the defense against experimental pathogens, there is a need of basic knowledge on cellular immune effectors also. The authors report here their experience in characterizing squirrel monkey blood T and B lymphocytes, and in studying in vitro induced activation and proliferation of T and B cells. Particular emphasis is given to the in vitro differentiation of squirrel monkey B cells into immunoglobulin secreting cells, with respect to Plasmodium falciparum antigens.

Detection of Actinobacillus pleuropneumoniae serotype 2 antibodies in pig sera by an inhibition enzyme immuno assay (EIA)

An inhibition Enzyme Immuno Assay (EIA) for detection of antibodies against A. pleuropneumoniae serotype 2 (App-2) in pig sera, based on the inhibition of the binding of an App-2 specific monoclonal antibody was established. The monoclonal antibody (mAb 102-G02) was found to be directed against an epitope on the O-chain of App-2 LPS. Some App-2 isolates did not react with the mAb 102-G02. These isolates are referred to as App-2X. In the inhibition EIA highly purified App-2 LPS ws used to coat microtiter plates. Serial dilutions of pig sera were added to the plates prior to the mAb 102-G02. The degree of binding of App-2 antibodies from pig sera was determined as the percentage inhibition of the mAb 102-G02. Pig sera from specific pathogen free (SPF) herds, from experimentally infected animals, and from conventionel herds were tested. A serum dilution of 1/200 was found to be optimal, when using 50% inhibition as the discriminating inhibition percentage. Serum from App-2X infected herds showed a lower reactivity as compared to serum from App-2 infected herds. No crossreactivity was observed with serum from pigs infected with other App serotypes. The sensitivity and specificity were 100% and 98.9%, respectively.

A dot-immunobinding assay for the demonstration of soluble Fc gamma receptors

We have developed a sensitive dot-immunobinding assay to demonstrate and characterize the functional activity of soluble Fc gamma receptors (FcR). Samples containing soluble FcR were immobilized on a nitrocellulose membrane. Immune complexes of horseradish peroxidase and rabbit IgG antibodies to horseradish peroxidase (HRP) were allowed to react with nitrocellulose-bound FcR, and the immune complexes were visualized by HRP developer. The intensity of the grey dots reflected the amount of immune complex bound. Binding of immune complexes to placental extract containing soluble FcR was inhibited completely by IgG and Fc fragments, but not by F(ab')2 fragments, IgA and IgM. The method was used to characterize the subclass specificity of solubilized placental FcR. Human Fc fragments, and intact IgG1 and IgG3 proteins inhibited the binding whereas preparations of F(ab')2, IgG2 and IgG4 did not. In conclusion, the dot-immunobinding assay described is a rapid and simple method for the demonstration and characterization of functionally active soluble FcR.

Squirrel monkey (Saimiri sciureus) B lymphocytes: secretion of IgG directed to Plasmodium falciparum antigens, by primed blood B lymphocytes restimulated in vitro with parasitized red blood cells

Blood B lymphocytes obtained from Plasmodium falciparum-immune Saimiri monkeys were assayed for their in vitro differentiation in immunoglobulin-secreting cells upon restimulation with P. falciparum-parasitized Saimiri red blood cells. Selected culture conditions enabled appropriately stimulated blood B cells to secrete 3F11/G10+ IgG, detected in the supernatants by means of a dot immunobinding assay. Primed blood B lymphocytes from P. falciparum-immune Saimiri monkeys were thus able to secrete IgG when restimulated by parasitized red blood cells in the presence of T cell- and monocyte-derived cytokines (recombinant human cytokines). These primed blood B cells, which were able to differentiate, were shown to secrete antibodies reactive with P. falciparum-infected red blood cells, as detected by means of an indirect immunofluorescence assay, and reactive with P. falciparum-infected red blood cell extracts, as detected by means of Western blot analysis. Furthermore, due to the possibility of discriminating between IgG subtypes in the squirrel monkey (3F11/G10+::3A2/G6+ IgG [associated with protection against the blood stages of P. falciparum] vs. 3F11/G10+::3E4/H8+ IgG [usually not functionally associated with protection]), we have attempted to estimate the respective proportions of each IgG subtype. In defined culture conditions, Saimiri monkey blood B cells preferentially secrete 3F11/G10+::3E4/H8+ IgG in response to parasitized red blood cells. We therefore discuss the conditions that would render this assay suitable for the selection, among P. falciparum blood stage antigens, of those that have major B-cell epitopes.

Quantitation of IgE and carcinoembryonic antigen (CEA) by optical beam deflection (OBD) measurement of dot-immunobinding assay patterns visualized by an ELISA technique

Dot-immunobinding assays of IgE and CEA were performed by a conventional dot-ELISA technique with diaminobenzidine staining, and the quantitative results were compared by densitometry and a new, spectroscopic, optical beam deflection (OBD) method using the same membrane. It was possible with the OBD method to detect quantities of these substances at least ten times smaller than with densitometry. Better intra-assay reproducibility for IgE and CEA measurements was obtained by the OBD method. The measurable ranges of the OBD method was broader than that of densitometry, because dark bands caused OBD in proportion to their color densities. When the dot-immunobinding assay with OBD measurement for CEA was also compared with a microtube ELISA using biotin-avidin conjugates, the sensitivities and reproducibilities of the two methods were found to be similar, with a correlation coefficient of 0.991.

Serum immunoglobulin class and IgG subclass levels and the occurrence of homogeneous immunoglobulins during the course of ageing in humans

Serum levels of IgM and IgA classes and of IgG subclasses were determined and related to the presence of homogeneous immunoglobulin components (H-Ig) in volunteers equally distributed in age groups from 25 to 98 years, who all met the Senieur admission criteria for immunogerontological studies. In addition, sera of non-Senieur volunteers aged 75 years and older were included. Furthermore, the amount of IgD was determined in sera of Senieur individuals equally distributed in age groups from 15 to 98 years. In the Senieur persons, the contribution of the IgG subclasses and the IgM and IgA classes to the pool of serum immunoglobulins remained relatively unchanged during the course of ageing. In comparison with Senieur individuals aged 25-34 years, a slight increase in IgM and IgA levels was observed from the age 35 to 44 onwards and in IgG1 from the age 55 to 64 onwards. The variability of the immunoglobulin concentrations increased during ageing. The most prominent observation was the continuous decline of serum IgD starting in young adults. The non-Senieur persons differed from their Senieur age-matched counterparts mainly by the elevated IgG2 and IgA levels. During the course of ageing, H-Ig mainly of low concentration were detected at an increasing frequency in the Senieur persons and even more frequently in the elderly non-Senieur volunteers. Although in some individuals the elevation of immunoglobulin levels correlated with the appearance of H-Ig within the corresponding isotype, this relationship was not conclusive for all sera investigated. These results suggest that the rise of serum levels of individual immunoglobulin isotypes associated with ageing is usually the consequence of a polyclonal B cell activation. The occurrence of H-Ig and the decline of serum IgD in aged Senieur persons indicate that these are, at least partly, true phenomena of ageing and not always the consequence of disease.

Antigenic specificities of glomerular-bound autoantibodies in membranous glomerulopathy induced by mercuric chloride

The present study describes the development of membranous glomerulopathy (MGP) with high proteinuria in DZB rats exposed to mercuric chloride (HgCl2). IgG1 and IgG2a antibodies, eluted from glomeruli with subepithelial immune deposits, bind to the interface of the GBM and epithelial cells. High reactivity to GBM was demonstrated by ELISA and Western blotting, which could be absorbed for 30% by laminin or laminin-associated extracellular matrix components. No reactivity was found with type IV collagen, fibronectin, heparan sulfate proteoglycans, or tubular brush border antigens. Absorption to GBM removed the reactivity to renal antigens. Passively transferred eluted antibodies bind in a predominantly linear pattern along the GBM, causing focal ultrastructural transformations of the podocytes. These results suggest that this type of HgCl2-induced MGP, associated with epithelial cell injury and proteinuria, is caused by autoantibodies to basement membrane components which are located at the epithelial cell-basement membrane interface and may be involved in cell-matrix binding.

IgG subclasses in bronchoalveolar lavage fluid from patients with asthma

We have measured Immunoglobulin G (IgG) subclasses in serum and bronchoalveolar lavage fluid (BALF) from 12 non-smoking patients with stable asthma and 9 non-smoking healthy volunteers to obtain information on their possible role in local immunological reactions. The quotients (concentration of IgG subclass in BALF)/(concentration of IgG subclass in serum) were calculated. In controls QIgG3 were lower than QIgG1, QIgG2 and QIgG4. The IgG subclasses in BALF and epithelial lining fluid (ELF) from patients with asthma were significantly higher than in controls, mainly due to increased leakage from the blood. Again QIgG3 were lower than Q of other subclasses. In the analysis of local production of IgG, albumin or ceruloplasmin was used as reference protein. Several patients showed a local production or a preferential accumulation of one or more IgG subclasses. We conclude that in healthy persons the IgG subclasses in ELF originate from the systemic circulation by passive permeation. In patients with asthma, the permeability of the respiratory membrane may be increased resulting in increased concentrations of subclasses in lung-lining fluid. In some patients with asthma, an additional local production of IgG subclasses occurs.

A quantitative dot immunobinding assay for coagulation factor XII in plasma

A dot immunobinding assay on nitrocellulose (NC) membranes has been developed for the quantification of human coagulation factor XII (F XII). Plasma samples were dotted on to NC filters and F XII was detected using a polyclonal antiserum followed by a radiolabelled antigen overlay. Dilutions of either pooled normal human plasma (NHP) or purified F XII in F XII deficient plasma were used as standards. Quantification was performed by measuring the radioactivity of bound 125I-F XII. Precise measurements of F XII antigen (F XII: Ag) were possible with a sensitivity down to 0.12 ng. Thus, dotting samples containing 0.5 microliter of plasma permitted detection of a F XII concentration corresponding to 1% of the level in NHP. The intra-assay coefficient of variation (CV) was less than 5% and the interassay CV was less than 16%. F XII:Ag in plasma samples of 50 healthy adults ranged from 12 micrograms/ml to 47 micrograms/ml. A good correlation (r = 0.93) existed between F XII:Ag and F XII clot promoting activity (F XII:C) in these samples. NHP contained 24.1 micrograms/ml F XII:Ag confirming earlier results obtained by other methods. In 16 pregnant women levels of F XII:Ag as well as of F XII:C were elevated, but F XII:Ag was disproportionately higher compared with F XII:C. The immunobinding assay has the following advantages: (1) rapid quantification of large numbers of samples is possible, (2) the sensitivity down to 1% of NHP is better than that of several other methods, (3) only very small amounts of both test material and reagents are needed.

Production and characterization of a human monoclonal antibody, reactive with a conserved epitope on gp41 of human immunodeficiency virus type I

A human Epstein-Barr virus-transformed lymphoblastoid B-cell line was generated from peripheral blood mononuclear cells (PBMC) of an asymptomatic human immunodeficiency virus type I (HIV-1) seropositive donor, which produces a human monoclonal antibody K14 (IgG1), reactive with an epitope on the transmembrane part (gp41) of the envelope glycoprotein of HIV-1. This monoclonal antibody reacts with a lysate of HIV-1-infected H9 cells, gradient purified HIV-1, and a vaccinia recombinant HIV-1 gp160 protein, but not with HIV-2 antigens in an enzyme-linked immunosorbent assay (ELISA). When used as an immobilized ligand in an immune affinity column, K14 selectively purifies gp41 from a HIV-1-infected H9 cell lysate. Although no reactivity was observed in ELISA with a panel of partially overlapping synthetic nonapeptides spanning the whole length of HIV-1 gp41, it was shown to react with recombinant envelope proteins, provided that they did contain amino acids 643-692: deletion of this part resulted in the disappearance of the reactivity. Testing of an extensive panel of the sera from HIV-1 seropositive or seronegative donors from Europe and Africa, including a selected group of donors before and after HIV-1 seroconversion, in a competition ELISA with horseradish peroxidase-conjugated K14, showed that the epitope recognized on gp41 is immunodominant and conserved. K14 does not neutralize HIV-1 infectivity or virus-mediated cell fusion, and does not mediate antibody-dependent cellular cytotoxicity.

Specificity and cross-reactive idiotypes of anti-glomerular basement membrane autoantibodies in HgCl2-induced autoimmune glomerulonephritis

Mercury-induced autoimmune glomerulonephritis in the Brown-Norway (BN) rat is characterized by the successive appearance of linear and granular glomerular IgG deposits. Anti-laminin autoantibodies represent the major part of the anti-glomerular basement membrane (GBM) antibodies produced in this model. Fusions were performed in this model and four anti-GBM monoclonal antibodies (mAb) were obtained. Three of them were laminin specific. Using rabbit anti-idiotype antibodies, cross-reactive idiotypes (CRId) were characterized on anti-laminin antibodies. They were expressed on the three anti-laminin mAb, on kidney-eluted and circulating anti-laminin antibodies. CRId-bearing immunoglobulins were detected transiently in the circulation and paralleled the anti-laminin antibody activity. By immunofluorescence studies on kidney cryostat sections two different CRId were defined. One was localized close to the antigen-combining site since it was not revealed on kidney-bound antibodies, in contrast with the second CRId. This latter CRId was also found deposited in a typical linear pattern in the early phase of the disease and in a granular pattern in the late phase, demonstrating that these CRId are components of immune deposits. Taken together, these results suggest that in this model of T-dependent polyclonal B cell activation, restricted sets of V genes encode for at least a part of the anti-GBM autoantibodies.

Inheritance of a large deletion within the human immunoglobulin heavy chain constant region gene complex and immunological implications

A deletion of the immunoglobulin heavy chain (IgH) pseudo-gamma, gamma-2, gamma-4, epsilon, and alpha-2 constant region gene segments was found to segregate unchanged in three generations of a family. The IgG1 locus on the IgH allele carrying the deletion was expressed to the same extent as its normal counterpart. One individual who was heterozygous for the deletion had an IgG2 deficiency, whereas the four other heterozygous individuals had serum levels of IgG2 and IgG4 within the normal ranges. IgA2 levels were low or below the normal range in all heterozygous individuals. The data indicate that the expression of some Ig isotypes can be decreased by hemizygous deletions, possibly due to a lower probability for switching.