ELISA measurement of IgG subclass production in culture supernatants using monoclonal antibodies

A coordinated cytotoxic effect of IFN-gamma and cross-reactive antibodies in the pathogenesis of Helicobacter pylori gastritis

BACKGROUND

Helicobacter pylori (H. pylori) infection is associated with chronic infiltration into the stomach by T cells and plasma cells producing IFN-gamma and antibodies of various specificities, respectively. It is unknown whether these lymphocyte-products may play coordinated roles in the gastric pathology of this infection.

AIMS

To know how IFN-gamma may relate to anti-H. pylori antibodies in their roles in pathogenesis, we determined the isotype subclass of those antibodies as well as their cross-reactivity and cytotoxicity to gastric epithelium.

METHODS AND RESULTS

We infected BALB/c mice with H. pylori (SS1, Sydney Strain 1) and generated monoclonal antibodies, which were comprised of 240 independent clones secreting immunoglobulin and included 80 clones reactive to SS1. Ninety percent of the SS1-reactive clones had IgG2a isotype. Two clones, 2B10 and 1A9, were cross reactive to cell surface antigens in H. pylori and to antigens of 28 KDa and 42 KDa, respectively, which were present on the cell surface of and shared by both mouse and human gastric epithelial cells. The antigens recognized by these monoclonal antibodies localized a distinctive area in the gastric glands. In the presence of complement, 2B10 showed cytotoxicity to gastric epithelial cells. The effect was dose dependant and augmented by IFN-gamma. Finally, administration of 2B10 to mice with SS1 infection aggravated gastritis by increasing cellular infiltration.

CONCLUSION

IFN-gamma by gastric T cells may participate in pathogenesis of the H. pylori infected stomach by directing an isotype-switch of anti-H. pylori antibodies to complement-binding subclass and by augmenting cytotoxic activity of a certain autoantibody. This may explain a host-dependent diversity in gastric pathology of the patients with H. pylori infection.

Placental transfer of IgG subclasses in a Japanese population

BACKGROUND

Maternal immunoglobulin G (IgG), transferred across the placenta to the fetus during intrauterine life, is an important component of the neonatal immunological defence mechanisms against infection. There is controversy with respect to differences in placental transfer of the different IgG subclasses, and no definite data are available on a Japanese population. Therefore, we investigated placental transfer of IgG subclasses in a Japanese population.

METHODS

A total of 228 matched pairs of cord and maternal serum samples (20-42 weeks gestation) were assayed for each IgG subclass by an enzyme-linked immunosorbent assay.

RESULTS

The mean values and hierarchy of cord/maternal concentration ratios of IgG subclasses at 40 weeks gestation were as follows: IgG1(1.47) > IgG3(1.17) = IgG4(1.15) > IgG2(0.80). The cord/maternal concentration ratios of all IgG subclasses were positively correlated to gestational age. The mean ratios for IgG1 and IgG4 nearly reached a plateau at 39 and 37 weeks gestation, respectively, while those for IgG2 and IgG3 increased until 41 weeks gestation. The ratios of all IgG subclasses for full-term deliveries were reciprocally correlated to the respective maternal IgG subclass serum levels.

CONCLUSIONS

The results suggest that although all four IgG subclasses are actively transferred across the placenta, the efficiency of their transfer ranks in the order IgG1 > IgG3 = IgG4 > IgG2. The different results as to placental transfer of IgG subclasses in the literature might be due, at least in part, to different maternal IgG subclass serum levels in the populations studied.

Immunoglobulin production by cultured human lymphocytes

The synthesis and secretion of immunoglobulin induced in cultured B-lineage cells is of interest for several reasons: (i) analysing the B-cell repertoire, (ii) recall of immunological activity retained in the circulating lymphocyte population, and (iii) study of factors needed for clonal expansion, immunoglobulin class switching, IgV-region mutation and maturation of cells to Ig secretion. Methods available are outlined and alternative procedures for cell separation and purification, helper cell provision and Ab/Ig assay systems are discussed. The aim is to provide practical guidance for those who intend to begin work in what is a vitally important, but experimentally difficult, area. There are a bewildering number of methods described in innumerable publications, old and new. The review provides a personal assessment of the present state of knowledge and prospects for improvements when all the new observations relating to cell-cell interactions and cytokines are integrated into existing technologies. The survey is chiefly concerned with physiologically based procedures, but artificial auxiliary methods are also briefly mentioned.

Analysis of IgG subclasses in chronic active Epstein-Barr virus infection

BACKGROUND

Although elevated serum levels of immunoglobulins are frequently observed in patients with chronic active Epstein-Barr virus (EBV) infection, there have been no reports concerning levels of IgG subclasses.

METHODS

Serum levels of IgG subclasses were measured by the enzyme-linked immunosorbent assay (ELISA) in 30 children with severe chronic active EBV infection.

RESULTS

Serum levels of IgG1 were elevated in most patients, except for one who showed an abnormally low level of IgG1 and progressive hypogammaglobulinemia. Serum levels of IgG2, IgG3 and IgG4 in the patients were comparable to those in control children, while abnormally low levels of IgG2, IgG3 and IgG4 were observed in six, three and four cases, respectively.

CONCLUSION

Although not always susceptible to bacterial infections, low levels of IgG2 were frequently observed in patients with chronic active EBV infection and elevated IgG1 is responsible for the increase of serum IgG in these patients.

Early immunopathological events in experimental ovine paratuberculosis

An experimental oral infection of neonatal (< 2 weeks old) lambs with a cervine isolate of Mycobacterium avium subspecies paratuberculosis (M.a. paratuberculosis), the causal agent of ruminant paratuberculosis (Johne's disease) was used to investigate bacteriological, histopathological and immunological changes during the early (up to 8 weeks) post-infection phase. In vitro culture for mycobacteria was positive in one faecal and three mesenteric lymph node (MLN) samples from the eight infected lambs. All mycobacterial isolates from MLN were identified as M.a. paratuberculosis by polymerase chain reaction (PCR). Small-to-medium sized focal granulomata were observed in jejunal (JPP) and ileal Peyer's patches (IPP) from four of the eight infected lambs. Compared with controls, JPP from all infected lambs had significantly (p < 0.05) higher proportions of CD8+ and CD2+ lymphocytes, and there were significantly (p < 0.05) fewer cells expressing B lymphocyte-associated markers in IPP and MLN. The T/B cell ratio was significantly (p < 0.05) increased in both JPP and MLN from infected lambs. The expression of a range of genes for cytokines was examined using specific reverse transcriptase PCR (RT-PCR) amplification of messenger RNA (mRNA) template isolated from MLN, JPP and IPP from both groups of animals. Densitometric analyses indicated that, in infected animals, MLN expressed significantly (p < 0.05) more mRNA for TNF-alpha: JPP had significantly increased (p < 0.05) mRNA for GM-CSF and significantly decreased (p < 0.05) mRNA for IL-4 and IFN-gamma. Infected lambs had significantly (p < 0.05) decreased titres of both circulating IgG and gut mycobacteria-associated IgG antibody. Infection was not associated with any consistent changes in lymphocyte reactivity to specific mycobacterial antigens, IFN-gamma release into supernatants from in vitro intestinal lymphocyte cultures or gut IgA antibody levels.

IgG subclasses in patients with membranoproliferative glomerulonephritis, membranous nephropathy, and lupus nephritis

Primary glomerulopathy can be classified into seven essential patterns based on histopathological studies. The pathogenesis of membranoproliferative glomerulonephritis (MPGN), and membranous nephropathy (MN), which show glomerular IgG deposition and induce mainly nephrotic syndrome, is not known. To clarify the role of IgG subclass in glomerulonephritis, we compared serum concentrations of IgG subclasses, the ratio of serum IgG subclasses to total IgG (%IgG subclass), and glomerular deposition of IgG subclasses between 7 MPGN patients, 21 MN patients, and 9 lupus nephritis (LN) patients. Serum IgG subclasses and %IgG in all groups were almost within normal range based on the values in Japanese healthy adults. In the MPGN and MN groups, the IgG1 concentration was significant lower than that of the LN group (P < 0.001, P < 0.0001, respectively). The IgG2 concentration in the MPGN group decreased significantly compared with that in the LN group (P < 0.05). The %IgG2 of the LN group decreased significantly compared with that of the MN group (P < 0.05). The %IgG3 of the MPGN group was significantly higher that that of the MN group (P < 0.05). The glomerular immunofluorescent intensity of IgG1 and IgG2 were significantly stronger in the LN group than in the MPGN and MN groups (IgG1, P < 0.001, P < 0.01, respectively; IgG2, P < 0.0001, P < 0.0001, respectively). IgG3 in the MPGN and LN groups deposited significantly compared with that in the MN group (P < 0.0001, P < 0.01, respectively). The intensity of IgG4 in the MN group showed a significant difference compared with that in the MPGN and LN groups (P < 0.0001, P < 0.01, respectively). IgG3 is an important factor in the pathogenesis of primary MPGN, while IgG4 relates to glomerular IgG deposition in MN.

Analysis of the expression and secretion of isotypes of sheep B cell immunoglobulins with a panel of isotype-specific monoclonal antibodies

Monoclonal antibodies to sheep light chain, IgM and IgG were produced and used to assess total immunoglobulin (Ig) synthesis by sheep B cells in culture and antibodies to specific antigens. By using these antibodies in a dual fluorescence-activated cell sorting analysis of sheep efferent lymph B lymphocytes the percentage change in surface Ig isotype of B lymphoblasts from IgM to IgG after the antigenic stimulation of the local lymph node was measured. An extension of this analysis to paired blood and afferent or efferent lymph B cells made it possible to investigate the recirculation characteristics of B cells expressing different Ig isotypes.

IgG2 deficiency associated with defects in production of interferon-gamma; comparison with common variable immunodeficiency

We report a novel mechanism of IgG2 deficiency. Several investigators have reported patients with IgG subclass deficiencies due to homozygous deletion of immunoglobulin heavy chain constant region genes. However, it is unclear what mechanism is responsible for IgG subclass deficiency in cases where no gene deletions have been detected and which are accompanied by recurrent infections due to aberrant immunoregulation. In the present study, we have focused our attention on production by peripheral blood mononuclear cells (PBMCs) of interferon-gamma (IFN-gamma), which is known to induce IgG2 expression. PBMCs from four patients with IgG2 deficiency and their families were studied. Mitogeninduced IFN-gamma production by PBMCs was decreased in all of the patients, although the proliferative responses of PBMCs and the percentages of CD3, CD4, and CD8 T cell subsets were not decreased. IgG2 production by PBMCs was restored upon addition of IFN-gamma and mitogen to the PBMCs of the patients with IgG2 deficiency though it was not restored in the patients with common variable immunodeficiency. We conclude that defects in production of IFN-gamma play an important role in IgG2 deficiency.

A case of common variable immunodeficiency associated with cyclic thrombocytopenia

A 12 year old boy was found to be deficient in immunoglobulins (Ig) A, G2 and G4, and common variable immunodeficiency was diagnosed. He also had cyclic thrombocytopenia at intervals of approximately 28-30 days. His bone marrow revealed normocellular with slightly decreased megakaryocytes. In vitro colony assays showed markedly imparied megakaryocytopoiesis, erythropoiesis and granulopoiesis. Platelet-associated IgG was elevated at his thrombocytopenic phase. Direct Coombs' test was repeatedly positive. Although not defined at present, we suggest the autoimmune nature of the disease.

IgG2 deficiency in methicillin-resistant Staphylococcus aureus infections after esophageal surgery

We previously reported the selective development of methicillin-resistant Staphylococcus aureus (MRSA) infections following esophageal surgery in patients with a reduced ability to produce anti-pneumococcal polysaccharide (PPS) IgG. Since the response to the PPS vaccine is correlated to the serum IgG2 levels, we measured IgG2 in the same series of esophageal cancer patients. IgG subclasses were determined in 21 patients, 8 of whom developed MRSA infections. IgG2 was thus found to be significantly lower (P < 0.01) in patients with MRSA infections (453 mg/dl) than in those without such infections (666 mg/dl). There was also a significantly positive correlation (r = 0.61) between anti-PPS IgG and serum IgG2. Therefore, the preoperative measurement of serum IgG2 is considered to be useful in detecting patients who are at risk for developing an MRSA infection after esophageal surgery.

Efficiency of induction of immunoglobulin synthesis by autologous human T cells and T cell clones: relation to surface isotype of the B cell

Efficient immunoglobulin (Ig) production was induced when human B cells were cultured with autologous T cells activated by immobilized CD3 mAb in cultures supplemented with IL-2. Negatively purified B cells or B cells positively selected with mAb to CD19, CD21 or CD72 surface antigens produced IgM, IgG and IgA, whereas B cells selected for surface IgD or IgM produced predominantly IgM indicating that little or no isotype switching was occurring. Results are compared with reports describing high levels of mu to gamma and mu to alpha switching in single B cell systems. The limited proliferation of B cells in our culture system may account for the difference. When untreated T and B cells were cultured together in the presence of immobilized CD3 mAb, B cell numbers peaked at 6-10 days whereas T cells continued to proliferate maximally. All 52 T cell clones tested induced the production of IgM, IgG and IgA from unselected or CD19 selected B cells, but efficiency of production of Ig overall and of the different isotypes varied with different T clones. All T clones which induced high IgM, IgG and IgA production induced IgE production too, but some less active T clones also induced IgE production under non-switching conditions indicating that direct contact with activated T clone cells efficiently induces IgE as well as IgG and IgA production from B cells already expressing these isotypes. Less Ig was produced with optimal numbers of untreated T clone cells than with X-irradiated cells, confirming that proliferating T cells can inhibit as well as activate Ig production from B cells.

Cultivation of the hybridoma cell line MN12 in a homogeneous continuous culture system: effect of culture age

The stability of the hybridoma cell line MN12 in a long-term homogeneous continuous culture was studied using a panel of analytical methods. These include two flow cytometry methods, for the determination of relative cytoplasmic and membrane IgG content. In addition, the antibody production was determined by an ELISA, and the metabolic state of the cells was determined by means of glucose consumption and lactate production. These results indicate a possible selection of variants of MN12 hybridoma cells with an overall aerobic metabolism, but with a higher glucose consumption rate and a higher lactate production rate. These variants are mainly characterized by a different membrane IgG content and cytoplasmic antibody content. These changes may possibly be affected by the culture age.

Quantitation of monoclonal antibodies by ELISA. The use of purified mouse IgG and mouse IgM monoclonal antibodies as standards in a quantitative ELISA measuring monoclonal antibodies produced by cell culture

Murine monoclonal antibodies (MAbs) of IgG1, IgG2a and IgG2b subclasses and IgM class in hybridoma culture supernatants were quantified using a sensitive, reliable, optimized indirect double antibody sandwich ELISA. In the ELISA, the MAb in the culture supernatants was sandwiched between affinity isolated heavy chain specific polyclonal antibodies used for capture and detection. Quantitation was achieved by comparison with a standard curve produced by a purified MAb of the same class, subclass or ideally the same clone as the MAb to be quantified. These quantitative results were compared with those obtained using purified IgG and IgM polyclonal serum samples as standards and those obtained by total protein estimation using measurement at OD280nm. The IgG subclass MAbs used as standards were purified using protein G and the IgM class MAb was purified by ion exchange followed by gel filtration chromatography. Bovine IgG contamination of the MAb supernatants and the purified MAbs was also measured by a double antibody sandwich ELISA.

IgG4 deficiency with Rothmund-Thomson syndrome: a case report

We describe a patient with Rothmund-Thomson syndrome and IgG4 deficiency. In vitro examination of his peripheral mononuclear cells revealed impaired IgG4 synthesis. Susceptibility to sinus and pulmonary infections was cured by monthly immunoglobulin infusions.

Normal levels of IgG subclass in childhood determined by a sensitive ELISA

Normal values of all IgG subclasses were determined using a sensitive ELISA in children aged from newborn to 14 years. The upper and lower limits of normal values of all IgG subclasses were obtained in all the age groups using 29 umbilical cord blood samples from full-term newborns and 308 venous blood samples from normal infants and children. The trends in the levels of IgG1, IgG2 and IgG3 with age were almost similar to previous reports. IgG4 levels decreased gradually until reaching the lowest level at 7 to 12 months and increased gradually with age, reaching a plateau at 12 to 14 years of age. Thus, the lower limit of serum IgG4 levels was determined using our method.

Serum immunoglobulin G subclasses and serum immunoglobulin A in acute bronchiolitis in infants

Serum IgG subclasses and Serum IgA were studied in 43 infants with acute bronchiolitis and 20 healthy infants. IgG subclasses were determined by a capture ELISA and IgA was quantified by turbidimetry. IgG1 concentrations were significantly lower in infants with bronchiolitis than in normal infants. The other IgG subclasses and IgA did not differ between the groups. The subgroups of infants with bronchiolitis who had previously suffered from otitis media or bronchitis, had significantly lower IgG2 than the other infants with bronchiolitis. The same was found for infants with bronchiolitis who had suffered from three or more lower respiratory tract infections. In infants who had suffered from upper or lower respiratory infections before the acute bronchiolitis, IgA was significantly higher than in infants without previous respiratory infections. Ten infants with bronchiolitis (23%) had IgG1 deficiency, that is values below the lower reference limit calculated in a population of healthy Norwegian infants. No healthy infants had any IgG1 deficiency. No infant with bronchiolitis had IgG2 or IgG3 deficiency. The low IgG1 values found in infants with acute bronchiolitis, may be one cause for infants to be more susceptible to RS virus infections.

C-fms protein expression by B-cells, with particular reference to the hairy cells of hairy-cell leukaemia

Although the hairy cells (HCs) of hairy cell leukaemia (HCL) are now thought to be a form of activated B cell, they have long been known to possess certain monocytoid characteristics. Since the proto-oncogene c-fms is a feature of cells of the monocyte/macrophage lineage, we examined HCs for c-fms expression. We found that approximately 80% of peripheral blood HCs expressed the c-fms protein (8/8 cases). Expression of the 150 kD protein by HCs was shown using three different techniques, APAAP, immunofluorescence and immunoprecipitation, using two different antibodies. Other mature B cell lymphoproliferative disorders examined (PLL, CLL and multiple myeloma) did not express c-fms. We also examined the c-fms expression of normal B-cells: both the in vivo activated (low density) fraction of tonsil B cells and tonsil B cells activated in vitro with SAC plus IL-2 expressed the c-fms protein. As in the case of monocytes c-fms expression by HCs was shown to be down regulated by its ligand M-CSF, and by TNF alpha, both caused a decrease in the receptor expression from 80% to 30% and in the intensity of staining from 6 to 3 x 10(4) molecules/cell. However, as for monocytes, GM-CSF treatment of HCs had no effect on the expression of c-fms; alpha IFN also had no effect. M-CSF treatment of HCs also induced phosphorylation of c-fms, and a number of other proteins, on tyrosine. However, M-CSF was unable to induce HC proliferation either alone or in combination with IL-2, IL-4 or IL-6; in addition it had no effect on HC proliferation induced by SAC, anti-mu or TNF alpha. In addition, M-CSF either alone, or in combination with the above cytokines, had no effect on the differentiated state of HCs as shown by both immunoglobulin secretion and surface antigen expression. M-CSF also had no effect on the morphology or long-term survival of HCs in culture. This study therefore demonstrates that both HCs and activated B-cells express c-fms, and that M-CSF binds to and activates its receptor on HCs. Although c-fms and several other proteins were shown to be phosphorylated in response to M-CSF, the functional consequences of this phosphorylation remain unclear.

Production and characterisation of a human monoclonal thyroid peroxidase autoantibody

A human-mouse hybridoma has been produced by fusion of Hashimoto thyroid lymphocytes with the mouse myeloma line X63-Ag8.653. The cloned hybridoma secreted 2.5 micrograms per 10(6) cells per day of an IgG kappa thyroid peroxidase (TPO) autoantibody (2G4) with high affinity (2.5 x 10(9) molar-1) and specificity for human TPO. 2G4 did not react with lactoperoxidase, horseradish peroxidase or human myeloperoxidase or with porcine TPO or with human thyroglobulin. Plastic tubes coated with 2G4 bound about 50% of 125I-labelled human TPO added and the binding was inhibited by IgGs prepared from 18/18 TPO autoantibody-positive sera. This indicated that all 18 sera contained autoantibodies which recognised the same (or closely related) epitope as 2G4. Plastic tubes coated with IgGs from different TPO autoantibody-positive patient sera also bound 125I-labelled TPO but inhibition by 2G4 in this system was not complete. This suggested that the sera contained at least 2 types of TPO autoantibodies, with only one type of autoantibody reactive with the same epitope as 2G4.

Abnormal immunoglobulin G subclass production in response to keyhole limpet haemocyanin in atopic patients

A proportion of patients with atopic dermatitis have elevated serum levels of IgG4. In order to investigate further this abnormality of IgG subclass production, atopic patients were immunized with the protein antigen keyhole limpet haemocyanin (KLH), and IgG subclass responses following primary and secondary immunization were analysed. In the primary response, titres of IgG1, 2 and 3 antibodies were lower in the atopic patients than in the controls. In contrast, titres of IgG4 were much higher for the patient group. In both patients and controls, the kinetics of IgG4 antibody production following the initial immunization with KLH showed a slow rise reaching a peak at 30 weeks. This time course indicated that the high IgG4 response was unlikely to be due to previous exposure of the patients to a cross-reacting antigen. A higher proportion of IgG4 was also seen in the atopic patients following secondary immunization; indeed, IgG4 was the major subclass in the secondary response in the patient group. In the controls, but not in the patients, titres of IgG4 anti-KLH correlated with total serum levels of IgG4, and some of the highest IgG4 antibody responses were detected in atopic patients whose serum IgG4 concentration was in the normal range. The results suggest that raised serum levels of IgG4 in atopy may reflect abnormal isotype regulation in response to protein antigens.

T-cell-dependent production of IgG by human cord blood B cells in reconstituted SCID mice

Reconstitution of severe combined immunodeficient (SCID) mice with human lymphocytes has recently allowed the elucidation of abnormalities of immune responses in various immunological disorders. In the present study, mononuclear cells (MNC) from neonatal cord blood and adult peripheral blood were intraperitoneally injected into SCID mice to examine induction of human Ig in respective mice recipients. Human IgG was consistently detected in the serum of SCID transferred with adult MNC, but only a few SCID recipients of cord blood MNC showed detectable but low levels of IgG in the serum. The combination experiments of isolated B and T cells disclosed that some interactions between B and T cells might be necessary for IgG production in transferred SCID mice. Notably, transfer of cord blood B cells with adult but not cord blood T cells resulted in efficient induction of IgG, associated with a change in subclass distribution. The results suggest that inability of neonatal B cells to produce IgG can be overcome by transfer with adult mature T cells into SCID mice.

Analysis of the IgG subclass production from rheumatoid arthritis synovial cell cultures

In man there are four subclasses of IgG which differ from each other with respect to their biological properties. Some evidence suggests that the production of IgG3 is unusually high in rheumatoid synovia. In this study secretion of IgG subclasses by synovial lymphocytes in vitro was measured using sensitive subclass-specific ELISAs. It was found that, in both synovial membrane- and synovial fluid-derived cell cultures, the general pattern of IgG subclass secretion was IgG1 greater than 2 greater than 3 greater than or equal to 4, and that, in most cultures, IgG3 was a minor subclass accounting, on average, for only 8% of the total IgG. This was similar to the percentage of this subclass in normal human serum and in culture supernatants from the patients' peripheral blood lymphocytes.

Selective IgG subclass deficiency: quantification and clinical relevance

Each of the four human IgG subclasses exhibits a unique profile of effector functions relevant to the clearance and elimination of infecting microorganisms. The quantitative response within each IgG subclass varies with the nature of the antigen, its route of entry and, presumably, the form in which it is presented to the immune system. This results in antibody responses to certain antigens being predominantly or exclusively of a single IgG subclass. An inability to produce antibody of the optimally protective isotype can result in a selective immunodeficiency state. This is particularly apparent for responses to certain bacterial carbohydrate antigens that are normally of IgG2 isotype. A failure to produce the appropriate specific antibody response may result in recurrent upper and/or lower respiratory tract infection. Careful patient investigation can identify such deficiencies and suggest appropriate clinical management. In this review we outline the biology and clinical relevance of the IgG subclasses and summarize current rational treatment approaches.

Quantitation of immunoglobulins produced by donor lymphocytes in transplant patients and the possible identification of donor cell-produced antiviral antibodies by imprint immunofixation

In the present study two patients were studied in detail to estimate the quantity of IgG of donor lymphocyte origin. Using IgG subclass quantitation and Gm haemagglutination inhibition titre, we estimated that up to 3% of IgG found after transplantation may be of donor lymphocyte origin. Analysis of viral antibody patterns by imprint immunofixation suggested polyclonal production of donor-derived antibodies.

Rat (and mouse) monoclonal antibodies. VIII. ELISA measurement of Ig production in mouse hybridoma culture supernatants

We describe a rat monoclonal antibody (MAb)-based solid-phase immunoenzymometric assay for the quantification of mouse hybridoma culture supernatant immunoglobulins (Igs). This assay involves the use of two rat MAbs, LO-MK-1 and LO-MK-2, which bind distinct mouse kappa light chain epitopes expressed by all murine kappa Igs. The assay permits reliable measurement of all murine kappa IgG subclasses in the 2-120 ng/ml range and murine kappa IgM class in the 2-30 ng/ml range. The intra- and interassay coefficients of variation in the measurement of Ig in mouse hybridoma culture supernatants averaged 7.5% and 5% respectively. The assay is simple, reproducible, rapid and does not require specific equipment. It is of potential value to all laboratories engaged in hybridoma technology.

The inductive effect of interleukin-4 on IgG4 and IgE synthesis in human peripheral blood lymphocytes

Using murine monoclonal antibodies against human IgG subclasses, specific and sensitive ELISAs assay to quantify the four human IgG subclasses in cell culture supernatants were established. The effect of human recombinant interleukin-4 (IL-4) on the regulation of IgG subclasses by normal peripheral blood lymphocytes was investigated. In addition to the enhancement of IgE synthesis, IL-4 preferentially induced IgG4 synthesis in vitro, whereas IL-4 had no effect on IgG1, IgG2, and IgG3 synthesis. IL-4-induced IgG4 production was blocked in a dose-dependent manner by recombinant interferon-gamma and anti-human IL-4 monoclonal antibody. Collectively, this data indicates that IL-4 plays an important regulatory role in both IgG subclass and IgE synthesis.

Characterization of antibody labelled colloidal gold particles and their applicability in a sol particle immuno assay (SPIA)

This study describes the characterization of antibody labelled colloidal gold particles and their applicability in a sol particle immuno assay (SPIA) to quantify murine monoclonal antibodies of all IgG isotypes. Two physical methods (transmission electron microscopy (TEM) and dynamic light scattering (DLS], were used to obtain information about particle size and morphology of the gold sols, but only with DLS antibody labelling could be detected. In addition, electrophoretic methods like agarose electrophoresis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed also that antibody labelling was successful. The biological activity of the antibody gold conjugates was determined by using them in a SPIA and as an electrondense marker in an immunogold labelling procedure to visualize meningococcal surface exposed outer membrane proteins labelled with monoclonal antibodies. The SPIA was applicable to determine murine monoclonal antibodies of all IgG isotypes with a sensitivity of 20-80 ng/ml and a coëfficiënt of variation of 6.7 +/- 2.2%.

A human-mouse hybridoma which secretes monoclonal thyroglobulin autoantibody with properties similar to those of the donor patient's serum autoantibody

Human monoclonal antibodies produced by Epstein Barr (EB) virus transformation and/or cell fusion are frequently IgM antibodies which tend to cross react with a range of antigens and often bear little relationship to the highly specific IgG antibodies associated with human autoimmune disease. By fusing EB virus transformed B lymphocytes from a Hashimoto patient with a mouse myeloma line and selecting for synthesis of IgG class thyroglobulin (Tg) antibody, we have developed a hybridoma (VB/5) secreting Tg antibody of IgG2 subclass and lambda light chain type which has the characteristics of a monoclonal antibody on isoelectric focussing. The antibody has a high affinity for human Tg and recognises Tg from other primates but not non-primate Tg. However, it does not react with human thyroid peroxidase or a panel of other autoantigens. In terms of affinity constant, functional affinity and affinity heterogeneity, the antibody closely resembles the IgG2 lambda Tg antibody present in the serum of the Hashimoto patient whose B lymphocytes were used to develop the hybridoma. In addition to providing a useful reference standard for Tg antibody IgG subclass assays, VB/5 antibody and the hybridoma line provide a valuable starting point for detailed studies of Tg autoantibodies and the genes coding for the variable regions of their heavy and light chains.

The regulation of IgG subclass production in man: low serum IgG4 in inherited deficiencies of the classical pathway of C3 activation

Human serum IgG subclasses have been measured by a sensitive enzyme-linked immunoassay in 52 subjects with severe genetic deficiency of a complement component. The mean serum IgG4 in 4 subjects with C3 deficiency was 8.2 micrograms/ml and in 14 subjects with C1-4 deficiency was 27.9 micrograms/ml. These means are severely depressed compared with the mean normal IgG4 of 292 micrograms/ml. IgG4 levels in C5-9 deficiency (175 micrograms/ml) and C1INH deficiency (179 micrograms/ml) did not differ significantly from normal. Serum IgG2 was reduced significantly, but far less severely than IgG4, in C3 and in some cases of C1-4 deficiency. IgG1 and IgG3 levels were within the normal range in all complement-deficient groups. Age differences between the groups do not explain the very low levels of IgG4 in C1-4 and C3 deficiency. These data suggest that serum IgG4 synthesis is dependent on an intact classical, but not alternative, pathway for activation of C3 and that IgG4-committed B cells require a complement-dependent maturation pathway not required by B cells committed to other IgG isotypes. IgG4 antibody responses are associated with secondary responses to T-dependent antigens. The possibility that IgG4 may be the product of a memory B cell which has been through a stage of differentiation in a germinal centre is discussed.