Long-term audiological follow-up of children with congenital cytomegalovirus

OBJECTIVE

To evaluate the audiological outcome of children with congenital cytomegalovirus infection.

METHODOLOGY

In a prospective study, the hearing of 98 congenitally cytomegalovirus-infected children born between January 2003 and July 2009 was systematically evaluated until the age of six using the Flemish CMV protocol. Symptomatic children with hearing loss at birth were treated with ganciclovir, if parents consented.

RESULTS

Seventy children passed initial screening, 28 had unilateral or bilateral hearing loss. In the normal hearing group, one asymptomatic and two symptomatic children developed late-onset hearing loss. Eight children in the group with hearing loss at birth received ganciclovir. Nine symptomatic and 11 asymptomatic children did not receive ganciclovir. In the treated group, 37.5% of the children had stable hearing loss, and 37.5% had progressive and/or fluctuating hearing loss. First progression or fluctuation always occurred after the age of one year. The hearing threshold improved in 25.0%. The improvement took place during or shortly after treatment. Hearing loss remained stable in 33.3% of the untreated symptomatic children, while progression or fluctuation occurred in 55.5%. In the asymptomatic group, hearing loss was most commonly stable (63.6%). The first change in the hearing threshold was almost always detected before the age of one year in both untreated groups.

CONCLUSIONS

Hearing loss caused by congenital cytomegalovirus infection cannot be defined unequivocally either with respect to the level of hearing loss or its evolution over time. Treating symptomatic children with ganciclovir leads to a better prognosis during the first year of life, after which progression or fluctuation again becomes more likely. However, overall, progression is more common in the untreated symptomatic group. Asymptomatic children with SNHL are more likely to have a stable hearing status.

Novel IgE peptide-based vaccine prevents the increase of IgE and down-regulates elevated IgE in rodents

BACKGROUND

Immunotherapy with anti-IgE antibodies for treatment of allergy is promising but a short half-life and extremely high cost limit its application.

OBJECTIVE

We sought to develop IgE vaccines that induce longer-lasting auto-antibodies to neutralize self-IgE as an alternative therapy.

METHODS

The vaccine was made by conjugating three synthetic peptides corresponding to human IgE receptor-binding sites to a carrier, hepatitis B surface antigen. To test the immunogenicity of the vaccine, rats were immunized with the vaccine or hepatitis B surface antigen as control. Serum IgG titres to human IgE and the IgE of other species were measured. The inhibition by rat antisera of the binding of human IgE to its receptor was assessed by ELISA, flow cytometry analysis, and passive cutaneous anaphylaxis (PCA), and its ability to recognize receptor-bound IgE was examined. The in vivo effect of the vaccine was evaluated in trichosanthin-sensitized mice and rats. In the preventative study, vaccination started before sensitization commenced, while in the treatment study, vaccination started after sensitization. Sensitized mice and rats receiving injections of the carrier served as controls. Trichosanthin-specific IgE was measured using PCA.

RESULTS

Sera from vaccine-immunized rats contained high titre antibodies that reacted with soluble and plate-bound but not with receptor-bound human IgE; they also reacted with mouse, rat, and dog IgE. Furthermore, the sera inhibited the binding of human IgE to its receptor in a dose-dependent manner. In preventative and treatment studies, serum trichosanthin-specific IgE levels were significantly reduced in vaccinated groups compared with controls.

CONCLUSION

Antibodies against self-IgE can be induced by IgE peptide-based vaccines, which are effective in preventing the increase of IgE and in down-regulating IgE in sensitized animals.

Regulation of B16F1 melanoma cell metastasis by inducible functions of the hepatic microvasculature

We have previously shown that circulating intravascular cells generally arrest by mechanical restriction in the hepatic sinusoids, causing rapid release of nitric oxide (NO) which is cytotoxic to these cells and inhibits their growth into metastatic tumours. Here, we present evidence that these NO-dependent cytotoxic mechanisms are susceptible to upregulation by lipopolysaccharide (LPS). Five x 10(5) fluorescently labelled melanoma cells were injected into the mesenteric vein of C57BL/6 mice to effect their localisation in the hepatic microvasculature. Test mice were then given 1 mg/kg LPS intraperitoneally (i.p.) to activate the microvascular cells. By electron paramagnetic resonance (EPR) spectroscopy, the expression of NO in the liver was significantly increased by 8 h in the LPS-treated mice. The non-selective NO synthase inhibitor L-NAME inhibited the induction of NO by LPS, while its inactive enantiomer D-NAME had no significant effect. Using immunohistochemistry (IHC), iNOS-positive microvascular cells were detected in the terminal portal venule (TPV) region of the liver 8 h after LPS stimulation. LPS treatment also increased the retention of melanoma cells in the liver between 8 and 24 h, especially in the TPV region. Eight hours after cell injection, local expression of VCAM-1 and ICAM-1 was detected by double-label immunohistochemistry at the sites of tumour cell arrest. Expression of these adhesion molecules was enhanced in mice treated with LPS. Using flow cytometry, 98% of the B16F1 melanoma cells expressed VLA-4, the counter receptor of VCAM-1, and approximately 1.5% expressed LFA-1, the counter receptor of ICAM-1. LPS did not significantly alter the expression of either counter receptor on melanoma cells in vitro or in vivo. By DNA end-labelling, the rates of melanoma cell apoptosis were significantly increased from 8 to 24 h in the TPV region (but not in the sinusoids) of LPS-treated mice. Fourteen days after tumour cell injection, the LPS-treated mice had a significantly smaller hepatic metastatic tumour burden than the control mice. These data suggest that LPS can inhibit the metastasis of melanoma cells in the liver by inducing the expression of NO and adhesion molecules by the hepatic endothelium. The induction of iNOS and the inducible cytotoxic effect of LPS appear to be primarily located within the TPV region of the liver acinus.

Functional status of the immune system after chronic administration of 2'-deoxycoformycin in the BB rat

Insulin-dependent diabetes mellitus (IDDM) is caused by autoimmune destruction of pancreatic beta cells with the primary mechanism being cell mediated. The BB rat develops insulitis and IDDM with many features analogous to the disease in man. In previous studies we reported that weekly administration of 2'-deoxycoformycin (dCF) for four months reduces significantly the incidence of IDDM in the BB rat by 70%, and that the animals remain free of diabetes for a minimum of two months after drug withdrawal. Since the diabetes-prone BB rat is lymphopenic, with a reduction of both CD4 and CD8 cells, the continuous failure of dCF treated animals to develop diabetes may have been due to generalized immunosuppression. To test this possibility, the ability of dCF treated diabetes-free BB rats to mount an immune response after challenge with Ovalbumin was examined five months after drug withdrawal. The results showed that the post-immunization levels of total IgG and specific IgG in these animals did not differ from those observed in non-dCF treated controls nor those of control diabetes-resistant non-lymphopenic BB rats. Moreover, FACS analysis indicated no change in the percentages of total numbers of CD4+ or CD8+ cells between the two groups of animals. Histological assessment of the pancreata of the post-dCF treated animals showed varying degrees of mononuclear cell infiltrates in the islets. These data demonstrate that treatment by dCF is not permanent, and may require intermittent or continuous administration to prevent development of diabetes. Further studies are needed to determine the mechanism of action of dCF in this model of IDDM.

[Evaluation of the antinociceptive effect of systemic and epidurally applied xylazine in general anesthesia with isoflurane in dogs and the effect of atipamezole infection on postoperative analgesia]

The alpha 2-selective adrenergic agonist xylazine has a long lasting antinociceptive effect (> 4 hours) after lumbosacral injection in dogs (Rector, 1996). The present study was performed to find out if epidurally administered xylazine acts locally as well as systemically. In a clinical investigation 30 dogs anesthetized with isoflurane in oxygen (1.9 Vol.% ET) were examined before and after epidural and intramuscular injection of xylazine (0.25 mg/kg) during surgery and over a 240-minute postoperative period. All dogs underwent surgery caudal the costal arch. The surgical patients were divided into three groups: group I: xylazine (0.25 mg/kg) epidural and aqua pro injectione i.m. (n = 10 dogs); group II: aqua pro injectione epidural and xylazine (0.25 mg/kg) i.m. (n = 10 dogs); group III: aqua pro injectione epidural and aqua pro injectione i.m. (n = 10 dogs). The division of xylazine epidural or i.m. or aqua pro injectione only was randomized. Prior to surgery, in all three groups somatic stimuli were exerted by pressure on the nailbed of a hind- and a forelimb before and after the epidural injection under general anesthesia. Heart rate, mean arterial pressure and rate of ventilation were used to determine the analgesic effect. During surgery, heart rate and mean arterial pressure were measured every 15 minutes. At the end of the operation, all patients were treated with the (alpha 2-selective adrenergic-antagonist atipamezole. During a 240 minute post operative examination heart rate, mean arterial pressure, rate of ventilation and reaction to pressure on the surgery site were used to determine the analgesic properties of xylazine. In this study it could be shown, that the concurrent epidural (group I) or intramuscular injection (group II) of xylazine in isoflurane anesthetized dogs leads to a better analgesic effect than isoflurane alone (group III) after somatic stimulation of a hind- and forelimb. From the antinociceptive effect in the forelimb after epidural administration of xylazine it was concluded that xylazine acts both locally as well as systemically. This was also confirmed by the hemodynamic changes, which were similar in group I (xylazine epidurally) and group II (xylazine i.m.). In the two groups treated with xylazine (group I and II), bradycardia and AV-blocks I and II were observed in three dogs during the first 30 minutes after epidural and intramuscular injection of xylazine. Hemodynamic changes were seen at the time of maximal plasma xylazine concentrations. One dog in the control group also had a bradycardia in connection with an AV-block II. During surgery no hemodynamic differences could be observed between the three groups. Heart rate was within normal limits and mean arterial pressure showed a slight hypotension. In agreement with the investigation of Rector (1996) it was shown in this study that xylazine has a long lasting (> 4 hours) antinociceptive effect after lumbosacral injection in the epidural space (group I). This analgesic effect is of local, spinal cord origin, as it was impossible to antagonize the analgesia by systemic application of atipamezole. In contrast to this, atipamezole reversed all analgesic properties totally after systemically administered xylazine in group II. However, sufficient analgesic plasma xylazine concentrations could only be detected in group II up to 180 minutes after injection. After this time period, an analgesic effect could not be expected anyway, even without antagonization. It can be concluded that the epidural administration of xylazine offers advantages in contrast to a systemic administration, as a longer lasting analgesic effect can be observed (after the epidural application), and systemic side effects can be reversed without effecting spinal analgesia.

Airway smooth muscle cell proliferation: characterization of subpopulations by sensitivity to heparin inhibition

Growth and maturation state of airway smooth muscle cells (SMCs) are determinants of asthma pathophysiology. Heparin reduces airway SMC proliferation and arterial SMC replication and phenotypic modulation. Distinct arterial SMC subtypes, differing in heparin sensitivity, have been characterized. We assessed the cellular mechanisms underlying the growth and phenotype of heparin-treated canine tracheal myocytes in primary culture. Heparin reduced replication by 40%. Immunoblot assay of myosin, actin, and myosin light chain kinase revealed heparin had no effect on rapid spontaneous phenotypic modulation after the cells were plated. Heparin increased cellular protein and vimentin contents in confluent cultures, suggesting that it may induce hypertrophic growth. Cell cycle analysis revealed that heparin decreased serum-stimulated replicating myocyte number by 40%. Also, G2-M transit was 20% slower for the set of SMCs that proceeded past G1 in the presence of heparin. These data indicate that heparin does not inhibit airway SMC replication by blocking modulation from the contractile state. Moreover, airway smooth muscle is composed of distinct SMC populations differing in mitogen and antiproliferative mediator responsiveness. Identification of functionally divergent subgroups suggests that distinct sets of SMCs may contribute differentially to airway physiology and pathophysiology.

Peripheral blood lymphocyte beta 2 integrin and ICAM expression in inflammatory bowel disease

The beta 2 integrin intercellular adhesion molecule (ICAM) adhesion pathway is likely pivotal in the immunopathogenesis of inflammatory bowel disease (IBD). We have undertaken a comprehensive study of peripheral blood lymphocyte (PBL) expression of all beta 2 integrins and ICAMs in patients with IBD using flow cytometry and assessed our data on the basis of IBD diagnosis, disease state of activity, and use of corticosteroids. Blood was collected from patients with Crohn's disease (N = 49), ulcerative colitis (N = 43), and normal control volunteers (N = 15). Mononuclear cells were separated using a Ficoll-Hypaque gradient and prepared for flow cytometry. The data were analyzed for percentage expression, mean fluorescent intensity (MFI) as well as for histogram patterns. The analysis was stratified for disease diagnosis, disease activity level, and for use of prednisone among patients with active disease. There was decreased percentage expression of CD11a, CD18, and ICAM-3 in Crohn's disease and ulcerative colitis compared with normal, but an increased MFI for these molecules among patients with Crohn's disease. Active Crohn's disease showed a greater change in this pattern compared with both inactive disease and active ulcerative colitis. CD11a and CD18 histograms typically had two peaks of expression. The predominance of one peak over the other varied with disease diagnosis and activity. CD11b and alpha d expression patterns were not different in IBD compared with normal. CD11c was not expressed by PBLs and, ICAM-2, typically an endothelial ligand, was expressed on PBLs. There were changes in the expression of beta 2 integrins in IBD, which were more evident in Crohn's disease than ulcerative colitis. We hypothesize that the decreased percentage expression and increased MFI of CD11a, CD18, and ICAM-3 may suggest that cells up-regulate these ligands following activation and are egressing into tissue.

Characterization of molecular determinants of smooth muscle cell heterogeneity

Broad diversity in contractile and pharmacological properties of different smooth muscles is well recognized. Differences in proliferative capacity, electrophysiology, phenotypic marker protein content, matrix synthesis, and expression of cell-specific transcription factors between individual smooth muscle cells (SMCs) have also been reported. Precise developmental and molecular mechanisms underlying heterogeneity are not known; however, their elucidation is the thrust of much current research involving vascular smooth muscle. In contrast, limited studies of heterogeneity of subtypes of airway SMCs are available. In this report, we review molecular aspects of differentiation that may determine phenotypic heterogeneity of SMCs and also present data from our own studies characterizing heterogeneity in the proliferative capacity and marker protein content of airway SMCs. Using flow cytometry, cell cycle transit was monitored for cultured canine tracheal SMCs. Only 70% of arrested cells responded and traversed the cell cycle when stimulated with 10% fetal bovine serum. Furthermore, heparin inhibited 40% of serum-responsive cells from entering the cell cycle, suggesting that both serum- and heparin-sensitive and -insensitive airway SMCs exist. Flow cytometric analysis of contractile protein and DNA content in freshly dissociated canine tracheal SMCs revealed that diploid (approximately 87%) and tetraploid (approximately 13%) populations exist. Clusters of SMCs having "high" or "low" smooth muscle myosin or alpha-actin content were also discerned, indicating that distinct subtypes of SMCs exist in mature airways. Diversity of SMCs may be a critical factor determining specific responses of smooth muscles to a number of physiological or pathophysiological stimuli that may include, for example, inflammatory mediators in asthmatic airways.

[Evaluation of the antinociceptive effect of xylazine after epidural administration in dogs under general anesthesia with isoflurane]

Seven dogs anaesthetized with isoflurane in oxygen (1.9 Vol.-% ET) were examined before and after lumbosacral injection of xylazine (0.25 mg/kg) into the epidural space. Over a 240 minute period the dogs were first stimulated in a visceral manner (extension of the colon descendens by a balloon-catheter) every 15 minutes. In a second part, the dogs were stimulated somatically by pressure to the interdigital skin of a hindlimb. Heart rate and mean arterial pressure were used to determine the analgesic properties of epidurally injected xylazine. Furthermore, plasma xylazine concentration was controlled in both series. Before epidural anaesthesia, heart rate and mean arterial pressure increased during stimulation significantly in both groups. After epidural injection of xylazine, hemodynamic reactions were distinctly diminished, in the somatically stimulated group more than in the viscerally stimulated group. Up to 30 minutes after epidural injection, plasma xylazine concentrations of about 100 ng/ml were found in both groups. Up to 60 minutes after epidural injection, plasma xylazine concentrations of more than 60 ng/ml still were found. From the 120th minute on, xylazine concentration decreased below 30 ng/ml. From these results, it can be concluded that there is a well-suited analgesic effect of epidurally applicated xylazine for approximately 240 minutes.

[Pharmacokinetics and effects of xylazine (Rompun) in dogs]

Six beagle dogs were treated with xylazine hydrochloride (1 mg/kg i.m.). The plasma xylazine concentration was measured by HPLC. Additionally, clinical effects were registered (cardiac rate, respiratory activity, electrocardiogram, body temperature, motoric activity, attention, analgesia). Maximum plasma concentrations were measured after 15 minutes (476 ng/ml). The plasma half-life was 24 minutes. Sedation was registered over one hour (xylazine concentration of more than 150 ng/ml). Within the first 30 minutes after treatment (xylazine concentration of more than 300 ng/ml), a low-grade analgesia was observed. In contrast, cardiac and respiratoric depression and also significantly diminished body temperature were registered over 2 to 3 hours.

Major histocompatibility complex class II-restricted cytotoxicity by self-myelin basic protein-reactive T-cell hybridomas: evidence for a tumour necrosis factor-independent nucleolytic mechanism

Direct cytotoxicity by class II-restricted T cells has been proposed as a potential mechanism in autoimmune tissue damage, as well as in immunoregulation. We used I-A(s)-restricted non-granular cytotoxic T-cell hybridomas (BP24.29 and BP47.7), specific for self-determinants on myelin basic protein (MBP), and different monoclonal targets, in order to characterize the mechanism of killing used by these cells. An early lesion at the level of the target cell nucleus was indicated by the fact that target DNA lysis ([3H]thymidine release) proceeded 2-2.5-fold as rapidly as cytoplasmic lysis (51Cr release) over the first 14 hr after stimulation. Cytotoxicity was relatively resistant to inhibition by anti-calcium agents (TMB-8 and verapamil), even under conditions which blocked interleukin-2 (IL-2) release. Although tumour necrosis factor (TNF) has been proposed as one mediator of class II-restricted cytotoxicity, these cells (i) released no detectable TNF after stimulation with antigen, concanavalin A (Con A), or anti-CD3, (ii) readily lysed TNF-resistant targets (A20 and LS-102.9), and (iii) had no cytotoxic effect on TNF-sensitive cells (L929). Substantial 'bystander' killing of I-A-mismatched targets was observed, which was 13-37% of the cognate (I-A(s)-restricted) cytotoxicity measured in parallel. This finding may indicate an effector mechanism in autoimmune demyelination, since the myelin-forming oligodendrocytes of the central nervous system are not inducible for major histocompatibility complex (MHC) class II expression.

Tumour necrosis factor alpha restores granulomas and induces parasite egg-laying in schistosome-infected SCID mice

Schistosomiasis (bilharzia) is a parasitic disease caused by several species of schistosome worms (blood flukes). The key pathogenic event in this disease is the formation of granulomas around schistosome eggs trapped in portal venules of the liver. Granulomas are a distinctive form of chronic inflammation characterized by localized aggregation of activated macrophages around an inciting stimulus. Each granuloma evolves to form a fibrous scar; in schistosomiasis, the result is widespread hepatic fibrosis and portal hypertension. To identify the specific immune signal molecules necessary for granuloma formation, we studied schistosome infections in severe combined immunodeficient (SCID) mice, which have normal macrophages but lack functional B or T lymphocytes. Here we report that the immunoregulatory cytokine tumour necrosis factor alpha is necessary and sufficient to reconstitute granuloma formation in schistosome-infected SCID mice. Moreover, we find that the parasitic worms require tumour necrosis factor alpha for egg-laying and for excretion of eggs from the host. The implication of this latter result is that the parasite has adapted so successfully to its host that it uses a host-derived immunoregulatory protein as a signal for replication and transmission.

Mapping of epitopes on Poa p I and Lol p I allergens with monoclonal antibodies

Allergen Poa p I isolated from the dialysed aqueous extract of Kentucky blue grass pollen by affinity chromatography with an anti-Lol p I murine monoclonal antibody (MAb) 290A-167 was previously shown to consist of a 35.8-kilodalton (kD) component with a pI of 6.4, designated as Poa p Ia, and a 33-kD component with a pI of 9.1, designated as Poa p Ib. The present study reports on the comparative antigenic analyses of these two components, using MAbs produced separately against Poa p I and Lol p I. Thus, anti-Poa p I MAbs 60 and 61 and anti-Lol p I MAb 290A-167 recognized Poa p Ia and Poa p Ib whereas anti-Poa p I MAbs 62, 63 and 64 and anti-Lol p I MAb 348A-6 recognized only Poa p Ia. The specificities of the MAbs were further resolved by comparing their respective abilities to inhibit the binding of 125I-Poa p I or 125I-Lol p I to the different MAbs prepared in the form of solid phase. These studies revealed that at least 4 distinct epitopes (designated as E1, E2, E3 and E4) were shared by both Poa p I and Lol p I. All 4 epitopes were present on Poa p Ia whereas only E1 and E3 were detected on Poa p Ib. E1 was recognized by MAbs 60 and 61, E2 by MAbs 62, 63 and 64, E3 by MAb 290A-167 and E4 by MAb 348A-6.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation and characterization of an alpha-satellite repeated sequence from human chromosome 22

We constructed a library in lambda L47.1 with DNA isolated from flow-sorted human chromosome 22. Over 50% of the recombinants contained the same highly repetitive sequence. When this sequence was used to probe Southern blots of EcoRI-digested genomic DNA, a ladder of bands with increments of about 170 bp was observed. This sequence comigrates with satellite III in Ag+/Cs2SO4 gradients and may account for at least part of the 170 bp Hae III ladder seen in isolated satellite III DNA. Partial sequence analysis revealed homology to the 171 bp monomeric repeat unit of alpha-R1-DNA and the X specific alpha-satellite consensus sequence. After low stringency in situ hybridization, silver grains were found over the centromeres of a number of chromosomes. Under high stringency conditions, however, the labeling was concentrated over the centromeric region of chromosome 22. This localization was confirmed using DNA from a panel of human/hamster cell lines which showed that the homologous 2.1 and 2.8 kb EcoR1 restriction fragments were chromosome 22 specific. These clones therefore contain chromosome 22 derived alpha-satellite sequences analogous to other chromosome-specific satellite sequences described previously.

Detection and characterization of monoclonal antibodies specific to IgE receptors on human lymphocytes by flow cytometry

BALB/c mice were immunized with human lymphoblastoid cells (RPMI 8866 cells) expressing surface receptors for IgE (Fc epsilon R). Spleen cells from animals displaying high titres of anti-Fc epsilon R antibodies were fused with HGPRT-deficient NSI myeloma cells. Anti-Fc epsilon R antibodies were identified by a flow cytometric assay based on their ability to block the binding of IgE-coated fluorescent latex particles to Fc epsilon R-positive cells. Fourteen monoclonal hybridoma cell lines secreting antibody of the required specificity were amplified in tissue culture and then grown in the peritoneal cavity of BALB/c mice in order to obtain ascitic fluids with high antibody titres. The specificity of each monoclonal antibody (Mab) to lymphocyte Fc epsilon R was shown by the following observations: (i) the intact monoclonal antibody molecule or, in some cases, its F(ab')2 fragments blocked the binding of IgE to several Fc epsilon R(+) cell lines different from that employed for the initial immunization; (ii) the Mab bound directly to all the Fc epsilon R(+) cell lines tested, but not to several Fc epsilon R(-) cells as determined by indirect immunofluorescence; (iii) the binding of Mab to Fc epsilon R(+) cells was selectively blocked by IgE, but not by the other classes of Ig; and (iv) Mab had no effect on the binding of IgG to Fc gamma R on normal human peripheral blood mononuclear cells (PBMC).

In vitro synthesis of IgE by human lymphocytes. IV. Suppression of the spontaneous IgE synthesis by IgE-binding factors secreted by tunicamycin-treated RPMI 8866 cells

It was previously shown that RPMI 8866 cells released IgE-binding factors (IgE-BFs) capable of enhancing the spontaneous in vitro synthesis of IgE by purified B lymphocytes isolated from allergic individuals. In the present study, the influence of tunicamycin, an inhibitor of protein glycosylation, on RPMI 8866 cells was investigated with regard to: (i) the expression of surface receptors for IgE; (ii) the release of IgE-BFs into the culture supernatants, and (iii) the biological activity of IgE-BFs. After preincubation for 60 min with tunicamycin (1 microgram/ml), RPMI 8866 cells were cultured for 48 hr in HB 101 serum-free medium; the culture supernatant was then filtered, concentrated, and its biological activity was compared to that of a parallel culture supernatant from untreated RPMI 8866 cells. The results of these experiments indicate that exposure of RPMI 8866 cells to tunicamycin resulted in: (i) a reduction of surface Fc epsilon R; (ii) no effect on the release of IgE-BFs into the culture supernatant, and (iii) the conversion of IgE-potentiating factors into IgE-suppressing factors. The latter factors suppressed the IgE secretion by U266 myeloma cells and completely inhibited the activity of IgE-potentiating factors on B lymphocytes from allergic individuals. IgE-BFs secreted by tunicamycin-treated cells had no effect on the production of IgG, IgA or IgM by normal or EBV-transformed B cells.

In vitro synthesis of IgE by human lymphocytes. I. The spontaneous secretion of IgE by B lymphocytes from allergic individuals: a model to investigate the regulation of human IgE synthesis

In view of the controversial data in the literature regarding the in vitro IgE synthesis by human lymphocytes, the conditions for culture of lymphocytes and the methodology for measurement of the IgE produced are described in detail. In the absence of any added mitogen, enriched B cell preparations derived from 70% of allergic donors actively secreted 100 to 3200 pg/ml of IgE after culture for 7 days, at which time the cell viability was higher than 85%. In comparable B cell cultures derived from non-allergic donors, only trace amounts of de novo synthesized IgE were detected in 20% of the cases. All B cell cultures actively secreted IgG, IgA, IgM and there was no apparent relationship between the secretion of IgE and that of the other classes of Ig. By contrast, the synthesis of IgE by unfractionated peripheral blood mononuclear cells of allergic individuals, which were stimulated with pokeweed mitogen (PWM) under several experimental conditions, was not consistently reproducible, i.e. the spontaneous synthesis of IgE in such cultures was either suppressed or enhanced by PWM. The most important finding was that the secretion of IgE was selectively enhanced by supplementing the B cell cultures with cell-free supernatants (CFS) of cultures of neonatal lymphocytes which had been preincubated with 10 micrograms/ml IgE. It is, therefore, concluded that B cell cultures from allergic individuals constitute an appropriate model for investigations of the mechanisms underlying the regulation of human IgE synthesis.

In vitro synthesis of IgE by human lymphocytes. III. IgE-potentiating activity of culture supernatants from Epstein-Barr virus (EBV) transformed B cells

Seven Epstein--Barr virus (EBV)-transformed B cell lines were derived from circulating lymphocytes of two atopic and two non-atopic individuals, two preparations of cord blood lymphocytes and one tonsillar lymphocyte preparation. All the cell lines contained a significant proportion of cells expressing Fc epsilon R as detected by rosette formation with IgE-coated bovine erythrocytes (E-IgE) and by flow cytometry using IgE-linked to fluorescent microspheres. None of the cell lines displayed FcR for IgA, IgM or IgG. The cell-free supernatants (CFS) of EBV-transformed cells contained IgE-binding factors (IgE-BFs) detected by their ability to inhibit the binding to RPMI 8866 cells of either E-IgE or IgE-linked to microspheres. Whereas these CFS enhanced the synthesis of IgE and suppressed the synthesis of IgG by purified B lymphocytes isolated from the blood of allergic donors and cultured in the absence of stimulant, their effect on the synthesis of IgA or IgM was not predictable. CFS significantly enhanced the secretion of IgE by the U266 myeloma cell line without interfering with secretion of IgM, IgG or IgA by EBV-transformed cells. These data are in accord with similar properties of RPMI 8866 cells and suggest that B lymphocytes might play a regulating role in the IgE synthesis.

In vitro synthesis of IgE by human lymphocytes. II. Enhancement of the spontaneous IgE synthesis by IgE-binding factors secreted by RPMI 8866 lymphoblastoid B cells

RPMI 8866 lymphoblastoid cells, known to express surface Fc epsilon R, were tested for their ability to regulate the in vitro synthesis of human IgE. Cell-free supernatants (CFS) of RPMI 8866 cells enhanced in a dose-dependent fashion the spontaneous IgE synthesis by B cells of allergic individuals. For maximum activity the CFS had to be added during the first 3 days of culture. CFS did not significantly alter the spontaneous synthesis of IgM or IgG, but they suppressed IgA synthesis both in B cell cultures and in pokeweed mitogen-stimulated peripheral blood mononuclear cells cultures. Cyclosporin A did not suppress either the spontaneous Ig production by B cells nor the IgE-potentiating activity of CFS. The enhancing activity of CFS was related to its content in IgE binding factors (IgE-BFs); these factors were detected by their ability to inhibit the rosetting of RPMI 8866 cells with IgE-coated erythrocytes (E-IgE). Both the IgE-BFs and the IgE-potentiating activity of the supernatants of RPMI 8866 cell cultures could be removed by absorption with IgE-Sepharose, from which they could subsequently be eluted with glycine-HCl buffer. IgE-BFs were identified as glycoproteins on the basis of their sensitivity to trypsin and to neuraminidase. By filtration of the RPMI 8866 cell supernatants through a Sephadex G75 column, IgE-binding activity was found to be associated with two fractions with molecular sizes in the range of 10,000-15,000 and 30,000-40,000. The IgA-suppressing activity of the RPMI 8866 culture filtrates could be absorbed with sIgA-Sepharose from which it was subsequently recovered by elution with glycine-HCl buffer. Most unexpectedly, sIgA-Sepharose also removed IgE-BFs and IgE-potentiating activity from the RPMI 8866 supernatants; both could be recovered by subsequent elution from sIgA-Sepharose with gycline-HCl buffer. These data are provisionally interpreted as indicating that the IgE-BFs secreted by RPMI 8866 cells had affinity for both IgE and sIgA and that they exerted a reciprocal effect on the in vitro synthesis of IgE and IgA.