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D Diaz-Sanchez

Publications and source records attributed to D Diaz-Sanchez.

At least 37 records · Page 2Linked to original sources
PubMed1995

Differential regulation of alternative 3' splicing of epsilon messenger RNA variants.

Alternative 3' splicing of the one active human epsilon heavy chain gene results in variants of epsilon mRNA encoding distinct IgE proteins. The same relative amounts of these epsilon mRNA variants were produced by non-atopic donor B cells when driven in a variety of T-dependent or T-independent systems. The most abundant variants were those for classic secreted epsilon a novel secreted form (CH4-M2"). In contrast, cells from subjects with high levels of serum IgE secondary to parasitic infection or atopy spontaneously produced higher relative levels of the CH4-M2' epsilon mRNA variant, lower relative amounts of both the membrane and CH4-M2" secreted variants, and very low levels of the CH4'-CH5 variant. The existence of and corresponding changes in levels of the CH4-M2'-encoded secreted protein were demonstrated. IL-10 induced this same differential expression of epsilon splice variants in vitro when used to costimulate IL-4 plus CD40-driven B cells and could differentially enhance the production of CH4-M2' protein by established IgE-secreting cell lines. Inhibition of IgE by cross-linking the low affinity IgE receptor (CD23) decreased the levels of epsilon mRNA and resulted in a distinct pattern of epsilon mRNA characterized by a dramatic decrease in CH4-M2' splice variant. IL-6, IL-2, or IFN-gamma did not change the epsilon mRNA pattern. Overall, the absolute and relative amounts of the different epsilon mRNA splice variants produced appear to be controlled in a differentiation-related fashion.

Adult↗
PubMed1995

Enhanced human IgE production results from exposure to the aromatic hydrocarbons from diesel exhaust: direct effects on B-cell IgE production.

Epidemiologic and experimental studies suggest that air pollution, and particularly diesel exhaust particles (DEPs) may play a role in the increasing prevalence and severity of airway allergic disease. We show that the extract of polyaromatic hydrocarbons (PAHs) from DEPs (PAH-DEP) enhances human IgE production from purified B cells. Interleukin-4 plus CD40 monoclonal antibody-stimulated IgE production was enhanced 20% to 360% by the addition of PAH-DEP over a period of 10 to 14 days. This effect was increased when PAH-DEP was added 2 to 5 days after cultures were initiated. PAH-DEP itself did not induce IgE production or synergize with interleukin-4 alone to induce IgE from purified B cells, suggesting that it was enhancing ongoing IgE production rather than inducing germline transcription or isotype switching. The prototype nonmetabolized aromatic hydrocarbon 2,3,7,8 tetracholorodibenzo-p-dioxin, which functions solely through activation of the cytosolic aromatic hydrocarbon receptor complex, also increased IgE production. Additionally, the pattern of mRNAs coding for distinct isoforms of the epsilon chain was altered by PAH-DEP, and B-cell expression of the low-affinity IgE receptor was upregulated by PAH-DEP. Enhanced IgE production in the human airway, resulting from exposure to PAH-DEP, may be an important factor in the increase in airway allergic disease.

Adult↗
PubMed1995

B cells from a distinct subset of patients with common variable immunodeficiency (CVID) have increased CD95 (Apo-1/fas), diminished CD38 expression, and undergo enhanced apoptosis.

We investigated the role of apoptosis in the differentiation failure of B cells from a selected subpopulation of patients with CVID delineated by B cell surface marker analysis, in vitro IgE response, and molecular markers of B cell VH gene repertoire. These patients had altered display of B cell surface molecules that play a role in apoptosis. The patients' B cells had a 4.5-250-fold increase in CD95 (Apo-1, fas) expression and increased CD95 display on their T cells. CD38, a molecule important in preventing germinal centre B cell apoptosis, was reduced on the patients' B cells. The expression of this molecule was inducible on the CVID lymphocytes with retinoic acid. Increased spontaneous apoptosis in vitro was observed with the patients' B (23%) and T cells (10%) compared with normal cells (13% and 3%, respectively). Stimulation in vitro with IL-4 and CD40 rescued the B cells from apoptosis and allowed for their differentiation. However, IL-4 plus alpha CD40-driven immunoglobulin production was not quantitatively or qualitatively normal. Failure to overcome apoptosis, a normal step in germinal centre B cell development, may be involved in the lack of differentiation seen in this subset of CVID patients.

ADP-ribosyl Cyclase↗
PubMed1995

The role of CD8+ T cells in immunoglobulin E regulation.

The link between immunoglobulin E (IgE) antibodies and environmental allergens, allergic sensitization and atopic diseases such as asthma, rhinitis and eczema is well established, yet treatment of these diseases is largely symptomatic and fails to correct the underlying immune disorder. B-cell production of IgE depends on interleukin 4 (IL-4) and is inhibited by interferon (IFN-gamma). These cytokines are produced by T-helper 2 (Th2) and T-helper 1 (Th1) CD4+ T cells respectively. In atopic dermatitis skin and asthmatic lung, Th2 cells predominate but antigen-specific CD4+ T-cell clones derived from peripheral blood are a mixture of Th1, Th2, and Th0. Circulating allergen-specific CD4+ T cells differentiate into Th1- and Th2-like clones in the presence of IL-12 and IL-4 respectively. In rats, CD8+ T cells are potent regulators of IgE responses in vivo, although the mechanism for this is still unclear. CD8+ T-cell depletion in immunized animals prolonged the IgE response but prior depletion did not. Indeed, prior depletion of CD8+ T cells actually inhibited IgE production, suggesting that there may be more than one type of IgE regulatory CD8+ T cell. This was supported by the observation that CD8+ T cells inhibited the differentiation of both Th1 and Th2 CD4+ T cells in vitro as well as IL-4- but not IL-2-induced Th2 CD4+ T-cell growth. The existence of distinct CD8+ T-cell subsets is supported by the observation that IL-4 and IFN-gamma regulate the growth and differentiation of CD8+ T cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Interleukin 4 activates a signal transducer and activator of transcription (Stat) protein which interacts with an interferon-gamma activation site-like sequence upstream of the I epsilon exon in a human B cell line. Evidence for the involvement of Janus kinase 3 and interleukin-4 Stat.

Germ line C transcripts can be induced by IL-4 in the human B cell line, BL-2. Utilizing a IFN-gamma activation site-like DNA sequence element located upstream of the I epsilon exon, we demonstrated by gel mobility shift assays that IL-4 induced a binding activity in the cytosol and nucleus of BL-2 cells. This factor was designated IL-4 NAF (IL-4-induced nuclear-activating factors) and was identified as a tyrosine phosphoprotein, which translocates from the cytosol to the nucleus upon IL-4 treatment. Because these are the characteristics of a signal transducer and activator of transcription (Stat) protein, we determined whether antibodies to Stat proteins will interfere with gel mobility shift and found that antibodies to IL-4 Stat, also known as Stat6, but not antibodies to other Stat proteins, interfere with the formation of the IL-4 NAF complex. Congruous with the involvement of a Stat protein, IL-4 induced robust Janus kinase 3 (JAK3) activity in BL-2 cells. Cotransfection of JAK3 with IL-4 Stat into COS-7 cells produced an intracellular activity which bound the same IFN-gamma activation site-like sequence and comigrated with IL-4 NAF in electrophoretic mobility shift assay. These results show that IL-4 NAF is IL-4 Stat, which is activated by JAK3 in response to IL-4 receptor engagement.

Animals↗
PubMed1995

Germ-line human epsilon heavy chain gene RNA transcripts utilize the full range of alternative 3' splicing seen in productive epsilon mRNA.

An early step in immunoglobulin isotype switching involves the initiation of active transcription of downstream heavy chain loci while they are still in germ-line configuration. This results in the production of 'sterile' germ-line RNA transcripts that do not contain VDJ sequences, the role of which in isotype switching is under intense scrutiny. We investigated whether such human epsilon germ-line transcripts employ the full complement of complex alternative 3' RNA splicing, splicing we have recently reported occurring with productive epsilon mRNA transcripts. Using a reverse transcriptase polymerase chain reaction (RT-PCR) strategy, in which the 5' primer was located in the I region of the epsilon gene, a region expressed in germ-line but not productive (VDJ containing) epsilon transcripts, we showed that the full range of alternative 3' epsilon splices occur with germ-line transcripts. These results demonstrate that epsilon 3' splicing events are independent of 5' isotype DNA switching. Additionally, we showed that, just as with mature epsilon mRNA, the relative production of the various epsilon germ-line mRNA isoforms was responsive to modulation by stimuli such as interleukin-10 (IL-10). Thus B cells, when stimulated to produce epsilon germ-line transcripts, generate a family of germ-line mRNA that differ not only in their initiation sites but, more importantly, also differ in their 3' sequences, sequences that could be important in regulation of the parent gene itself. Furthermore, by discontinuous or trans-splicing, cells could utilize these various epsilon germ-line transcripts to produce the full range of mature IgE proteins prior to undergoing deletional recombination of isotype switching.

Base Sequence↗
PubMed1994

CD58 (LFA-3) stimulation provides a signal for human isotype switching and IgE production distinct from CD40.

Induction of an IgE response involves several discrete steps: 1) induction of epsilon germ line transcription, 2) DNA recombination, and 3) mature RNA transcription/translation. Here we show that ligation of B cell CD58 by CD2, its natural ligand on T cells, or by mAb, provides a novel IL-4-dependent signal for the latter two steps. Highly purified human B cells were induced to produce IgE by costimulation with IL-4 and CD58 mAb. Although CD58 ligation alone was unable to induce epsilon germ-line transcription, in concert with IL-4-stimulated epsilon germ-line transcription it induced the appearance of productive epsilon transcripts and IgE production. The direct involvement of CD2 was demonstrated: B cells cultured with IL-4 plus murine T hybridoma cells transfected with human CD2 produced IgE. A CD40 Fc fusion protein had no effect on CD58-driven IgE production while inhibiting CD40-dependent responses. Furthermore, cells from patients with common variable immunodeficiency produced IgE in response to IL-4 plus CD40 mAb but not to IL-4 plus CD58 mAb. CD58-driven IgE synthesis was IFN-gamma independent and was not enhanced by exogenous IL-6. Functional differences between CD40 and CD58 IgE stimulation were demonstrated. Thus, the CD2:CD58 ligand/counterligand system provides an alternative pathway by which cell contact signaling may regulate IgE. Given the relative importance of CD2 triggering on mucosal T cells and the mucosal location of IgE production, this may be especially true on mucosal surfaces.

Adult↗
PubMed1994

Immune regulation: a new role for the CD8+ T cell.

During an immune response, peripheral T cells develop into functionally distinct subpopulations that effect cell-mediated immunity and regulate humoral immune responses through the secretion of specific cytokines. Recent data suggest that CD8+ T cells, which have long been regarded simply as cytotoxic cells, play a more active role in the regulation of the immune response. In this article, Mike Kemeny and colleagues suggest that there are functionally distinct subsets of CD8+ T cells that produce different combinations of cytokines and appear to play an important part in determining the pattern of cytokines produced by CD4+ T cells and the isotype of immunoglobulins expressed by B cells.

Animals↗
PubMed1994

Diesel exhaust particles induce local IgE production in vivo and alter the pattern of IgE messenger RNA isoforms.

Diesel exhaust particles (DEP) have been implicated in the increased incidence of allergic airway disorders. We investigated the effects of DEP on localized immunoglobulin production by performing nasal challenges with varying doses of DEP and analyzing the local immune response in nasal lavages obtained before and after. A significant rise in nasal IgE but not IgG, IgA, IgM, or albumin was observed in subjects 4 d after challenge with 0.30 mg DEP, equivalent to exposure on an average Los Angeles day. Direct evidence for DEP-enhanced local production of IgE was that challenge increased the number of IgE-secreting cells in lavage fluid from < 1 in 2,000,000 to > 1 in 100,000 but did not alter the number of IgA-secreting cells. There was a concomitant increase in epsilon mRNA production in the lavage cells. Additionally, DEP altered the relative amounts of five different epsilon mRNAs generated by alternative splicing, mRNAs that code for different IgE proteins. These results show that DEP exposure in vivo causes both quantitative and qualitative changes in local IgE production. The implication is that natural exposure to DEP may result in increased expression of respiratory allergic disease.

Adult↗
PubMed1993

Ricin enhances IgE responses by inhibiting a subpopulation of early-activated IgE regulatory CD8+ T cells.

Ricin, a toxic lectin from castor beans greatly enhances IgE responses to bee venom phospholipase A2 (PLA2) in high and low IgE responder strains of rat. The increase in IgE is accompanied by a 60% reduction in the number of CD8+ but not CD4+ T cells in the spleen. Optimal enhancement of IgE by ricin occurs when it is given at the same time as the antigen or 24 hr later, suggesting that it acts on cells which were activated as a consequence of immunization. Radio ligand-binding studies with 125I ricin were used to compare the number of ricin binding sites on CD4+ and CD8+ T cells. No difference was seen in either the affinity or the number of receptors for ricin on the CD4+ and CD8+ T cells of unimmunized rats. In contrast, CD8+ T cells taken from rats which had been immunized with 10 micrograms of PLA2 24 hr earlier demonstrated considerably more ricin receptors (3.9 x 10(7) +/- 2.2 x 10(6) binding sites/cell) than CD4+ T cells (3.19 x 10(6) +/- 1.08 x 10(6) binding sites/cell). However the affinity of the receptors for ricin was unchanged. Cytofluorographic analysis with fluorescein isothiocyanate (FITC)-labelled ricin confirmed these observations and indicated that increased ricin binding occurred on a subpopulation of CD8+ T cells. The effect of CD8+ T cells on IgE regulation was investigated by adoptive transfer. 1 x 10(8) highly purified (> 98%) splenic CD8+ T cells collected from Brown Norway rats 3 days after immunization with 10 micrograms of PLA2 were adoptively transferred to naive, syngeneic recipients. The IgE antibody response to PLA2 + A1(OH)3 seen in these animals was reduced by 91%. Adoptive transfer of CD4+ T cells from the same donor animals did not induce suppression and nor did adoptive transfer of CD8+ T cells from animals given both ricin and PLA2. However, when recipients of CD8+ T cells taken from rats immunized with PLA2 were immunized with a different antigen [ovalbumin (OVA)] and A1(OH)3 the IgE antibody response was also suppressed, although to a lesser extent (66%). These results show that co-administration of ricin and PLA2 depletes a subpopulation of ricin-sensitive, early activated CD8+ T cells and that these CD8+ T cells are potent suppressors of the primary IgE response.

Animals↗
PubMed1993

Elimination of IgE regulatory rat CD8+ T cells in vivo increases the co-ordinate expression of Th2 cytokines IL-4, IL-5 and IL-10.

Immunization of rats with soluble antigen (ovalbumin) and the castor bean toxin, ricin, eliminates a subpopulation of CD8+ T cells which suppress IgE responses in vivo. This treatment also reduces the ability of splenic T cells to produce interferon-gamma (IFN-gamma) and enhances their capacity to make interleukin-4 (IL-4). In this report we describe the effect of immunization with ricin and antigen on the expression of mRNA for other T-helper type 2 (Th2) cytokines--IL-5 and IL-10--and their relationship to serum IgE and IL-4 mRNA expression. Splenocytes were taken from rats at different times after immunization with antigen or ricin and antigen and activated in vitro with phorbol myristate acetate (PMA) and ionomycin for 6 hr and total RNA extracted and reverse transcribed. Cytokine gene expression was detected using a quantitative polymerase chain reaction (PCR). Expression of IL-4, IL-5, and IL-10 was increased 7-20-fold 11 days after immunization with ricin and antigen (from 0.107% to 0.769% beta-actin for IL-4, from 0.0167% to 0.381% beta-actin for IL-5, and from 0.0581% to 0.954% beta-actin for IL-10), and preceded maximum serum IgE levels by 4-5 days. There was no increase in IgE or mRNA for these cytokines in rats immunized with antigen alone. The level of IL-4, IL-5, and IL-10 expression declined rapidly after 12 days. Our results suggest that immunization with antigen and ricin preferentially induces a Th2 response, and that CD8+ T cells may play a part in down-regulating the development of Th2 T cells.

Animals↗
PubMed1993

Elimination of IgE regulatory rat CD8+ T cells in vivo differentially modulates interleukin-4 and interferon-gamma but not interleukin-2 production by splenic T cells.

Intraperitoneal immunization of Hooded Lister rats with a soluble antigen such as bee venom phospholipase A2 (PLA2), or ovalbumin (OVA) together with the toxic lectin, ricin, eliminates a population of early-activated CD8+ T cells which regulate IgE production. These early-activated CD8+ T cells are eliminated because they bear increased ricin-binding glycoproteins on their surface. This immunization regimen produces a vigorous and long-lived IgE response. The effect of this treatment on the capacity of splenic T cells to secrete interferon-gamma (IFN-gamma), interleukin-2 (IL-2) and to generate IL-4 RNA message was assessed. IFN-gamma production by phytohaemagglutinin (PHA)- or ionomycin and phorbol myristate acetate (PMA)-stimulated splenocytes or purified splenic T cells from animals immunized with antigen and ricin was substantially reduced as compared with animals which were given saline or antigen alone (P < 0.001 Student's t-test). At the height of the primary IgE response IFN-gamma production by PHA-stimulated splenocytes was positively correlated with the number of CD8+ T cells (r = 0.90, P < 0.001) and inversely related to the level of serum IgE (r = -0.77, P < 0.020); serum IgE was inversely related to the number of CD8+ T cells (r = -0.92, P < 0.001). The reduced capacity of spleen cells from ricin and antigen immunized rats to produce IFN-gamma was first seen 7 days after immunization. The fall in the ability of splenocytes to secrete IFN-gamma closely paralleled the rise in serum IgE. IL-2 was assayed using an IL-2-dependent cell line which responded to rat IL-2 but not IL-4. Production of IL-2 by splenocytes taken from rats immunized with ricin+antigen was not significantly different to that produced by comparable cells obtained from animals immunized with antigen alone or saline. However, the levels of IL-4 mRNA, detected in ionomycin and PMA-stimulated splenocytes using a quantitative polymerase chain reaction (PCR) procedure, were three- to fourfold higher in ricin and antigen immunized animals as compared with control animals. Following boosting with antigen and ricin the levels of IL-4 message detected increased a further three- to fourfold. These data show that the potentiated IgE response produced by immunization with antigen+ricin is associated with a decreased ability of splenocytes to produce IFN-gamma and an increased capacity to make IL-4.

Animals↗
PubMed1991

Role of CD8 T cells in rat IgE responses.

The role of the cytokines interleukin-4 and interferon-gamma in the regulation of IgE responses in the mouse and man have focused on the role of CD4 T cells. In the rat, antigen-specific CD8 T cells, generated following inhalation of antigen, have been shown to be capable of suppressing IgE responses. Repeated intraperitoneal injections of 1 ng ricin and 1 microgram antigen established a long-lived IgE response in both low- and high-IgE responder rat strains (Wistar and Brown Norway). The duration of the IgE antibody response was 204 and 248 days, respectively. Total IgE levels rose from 30 +/- 20 to 39,000 +/- 7,500 ng/ml in the Wistar rat and from 120 +/- 100 to 47,000 +/- 8,000 ng/ml in the Brown Norway rat. An even greater (10(4)-fold) increase was seen in antigen-specific IgE antibody levels. Ricin alone had no effect and concomitant or prior stimulation with antigen was required. The proportion of CD4+ and CD8+ cells present in the spleen at the peak of the IgE response was markedly increased compared with animals given ricin or antigen alone. Furthermore, CD8 T cells were approximately 100 times more sensitive to ricin than CD4 T cells. These data suggest that enhancement of IgE responses in ricin-treated animals results from the selective deletion of T cells which suppress IgE and are of the CD8 phenotype.

Animals↗
PubMed1991

Generation of a long-lived IgE response in high and low responder strains of rat by co-administration of ricin and antigen.

Certain strains of rats infested with the nematode parasite Nippostrongulus brasiliensis mount vigorous, persistent immunoglobulin E (IgE) responses. In the absence of parasites, adjuvants such as Bordatella pertussis or Al(OH)3 are needed to produce IgE responses to soluble antigens. These are short-lived, even in high IgE responder strains. In this study we have produced long-lived IgE responses in both low (Wistar) and high (Brown Norway) IgE responder strains of rats by repeated injections of ricin, a toxic lectin from castor beans, and phospholipase A2 (PLA2), a bee venom protein. Total IgE levels rose from 30 +/- 20 ng/ml to 39,000 +/- 7500 ng/ml in the Wistar rats compared with an increase from 120 +/- 100 ng/ml to 47,000 +/- 8000 ng/ml in the Brown Norway rats. An even greater (10(4)-fold) increase was seen in PLA2-specific IgE antibody levels. total and PLA2-specific IgE started to fall 6 weeks after treatment was stopped in the Wistar and after 12 weeks in the Brown Norway rats. The duration of the response was 204 and 248 days, respectively. The IgE-enhancing properties of ricin were compared in low, mid (Hooded Lister) and high IgE responder rats. Total IgE and PLA2-specific IgE but not IgG antibody (Ab) responses were enhanced in all animals given ricin and PLA2 but not in animals given ricin or PLA2 alone. The increase was greater in Wistar rats (48-fold) than in Brown Norway rats (eightfold) and by Day 24 the levels of both total and PLA2-specific IgE in three different strains were indistinguishable. PLA2-specific IgE antibody-secreting cells were detected in the spleen at a frequency of 1:5000. These results show: (i) that repeated immunization of rats with antigen and ricin produce a very large IgE response which was long-lived; (ii) that this response was indistinguishable in different IgE responder strains of rat; and (iii) that the IgE response declines earlier in low IgE responder strains of rats.

Adjuvants, Immunologic↗
PubMed1990

The sensitivity of rat CD8+ and CD4+ T cells to ricin in vivo and in vitro and their relationship to IgE regulation.

In a previous paper we described how the toxin ricin stimulates IgE but not IgG antibody responses in rats. In this study we have examined the cellular basis for this observation. The proportion of CD4- and CD8-positive cells present in the spleen at the peak of the IgE response was determined. Those animals injected with both ricin and antigen produced a substantial IgE response (50-fold increase). Their CD4+/CD8+ ratio was also markedly increased (P less than 0.001) compared with animals given toxin or antigen alone. In addition, mitogen-stimulated proliferation of mononuclear cells from spleens of the IgE-producing rats was enhanced nearly five-fold compared with cells from animals given toxin or allergen alone. The sensitivity of CD4- and CD8-positive rat spleen cells from unexposed animals to ricin in vitro was also studied. Spleen cells from untreated rats were co-cultured with optimal doses of mitogen and varying amounts of ricin. Mitogen-driven proliferation was inhibited at 10(-3) - 10(-6) mg/ml ricin. This effect was abrogated by the addition of as little as 0.01 M lactose but not by as much as 10 mg/ml mannan to the culture. Cultures depleted of CD4+ cells by rosetting were approximately 100 times more sensitive to ricin (P less than 0.01). Furthermore, the proportion of CD8+ to CD4+ cells present after culture of untreated cells with mitogen and ricin was significantly reduced. These results show (i) that the ability of ricin to increase the IgE response depends on the administration of antigen together with the toxin; (ii) that CD8+ spleen cells are more sensitive to ricin than CD4+ cells; (iii) that increased IgE responsiveness is associated with a reduction in the proportion of CD8- relative to CD4-positive cells in the spleen and increased responsiveness to mitogen. We believe that enhancement of the IgE responses by ricin may be due to inactivation of IgE-specific T-suppressor cells generated by immunization with antigen and speculate that these may be some or all of those bearing the CD8 marker.

Adjuvants, Immunologic↗