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W Strober

Publications and source records attributed to W Strober.

At least 109 records · Page 6Linked to original sources
PubMed1994

Differential regulation of C alpha 1 and C alpha 2 germ-line and mature mRNA transcripts in human peripheral blood B cells.

In this study, we investigated the regulation of germ-line and mature C alpha mRNA transcript expression in human peripheral blood B cells. In initial studies, we found that C alpha germ-line and mature transcripts were constitutively expressed in total peripheral blood B cells but not in high density surface IgM+ (surface IgA-) B cells; the latter cells were therefore used in subsequent studies. Focusing first on regulation of germ-line (I alpha-C alpha) transcripts, we showed that C alpha 1 germ-line transcripts are induced by TGF-beta 1 alone but such induction is enhanced by Staphylococcus aureus, Cowan I (SAC). In contrast, C alpha 2 germ-line transcripts are optimally induced by TGF-beta 1 in the absence of a B cell stimulus. In addition, although SAC alone induced both C alpha 1 and C alpha 2 germ-line transcripts, such induction is dependent on endogenous (B cell-derived) TGF-beta 1 production, because no induction is detected in cells cultured in the presence of neutralizing anti-TGF-beta 1. Turning next to mature (VDJ-C alpha) transcripts we showed that SAC plus TGF-beta 1 induces mature C alpha 1 transcripts, and such induction is IL-10 dependent because it is enhanced by exogenous IL-10 and abrogated by the presence of anti-IL-10. In contrast, SAC plus TGF-beta 1 does not induce C alpha 2 mature transcripts, even in the presence of exogenous IL-10; such transcripts are induced, however, by T cell stimuli such as anti-CD40 (presented by CDw32-transfected L cells) in the presence of TGF-beta 1/IL-10 or by PWM-activated T cells. In summary, these studies show that C alpha 1 and C alpha 2 germ-line transcript induction is differentially regulated, in keeping with previous studies of differences in germ-line CH transcript induction in the first and second IgH duplication units. Furthermore, C alpha 1 and C alpha 2 mature transcript induction is also differentially regulated, with C alpha 2 requiring a T cell signal such as that delivered by the CD40 ligand. Finally, IL-10 appears to be uniquely supportive of the induction of both C alpha 1 and C alpha 2 mature transcripts.

B-Lymphocytes↗
PubMed1994

The murine Ig 3' alpha enhancer is a target site with repressor function for the B cell lineage-specific transcription factor BSAP (NF-HB, S alpha-BP).

Using electrophoretic mobility shift assays (EMSAs) we have identified several target sites for nuclear proteins in the murine heavy chain Ig 3' alpha enhancer. Two of these sites, denoted oligo-H and oligo-K, were shown by several criteria, including cell distribution and stimulation experiments, EMSA cross-competition studies, and proteolytic clipping bandshift assays, to bind to the same protein identical to the transcription factor B cell lineage-specific activator protein (BSAP) (NF-HB, S alpha-BP). To assess the possible functional role of these BSAP binding sites in the 3' alpha enhancer, we transiently transfected a construct containing a 314-bp 3' alpha enhancer fragment upstream of a luciferase reporter gene in MOPC-315 cells, a plasmacytoma line lacking BSAP. In these cells, co-transfection with a vector expressing recombinant BSAP led to significant reduction in the activity of the 3' alpha enhancer fragment. Conversely, in the mature B lymphoma cell line CH12.LX, a cell line that expresses BSAP and has a less active 3' alpha enhancer, selective BSAP down-regulation by an antisense phosphorothioate oligonucleotide was sufficient to considerably up-regulate 3' alpha enhancer activity, as were mutations of both binding sites that prevented binding of BSAP to the 3' alpha enhancer. Our findings thus suggest that the natural loss of BSAP expression in terminally differentiated plasma cells contributes to the activation of the murine Ig 3' alpha enhancer.

Animals↗
PubMed1994

B cell differentiation defects in common variable immunodeficiency are ameliorated after stimulation with anti-CD40 antibody and IL-10.

In these studies we show that although purified B cells of patients with common variable immunodeficiency (CVI) have a normal capacity to proliferate, they manifest differentiation defects at multiple levels. Compared with controls, circulating CVI B cell populations contain reduced numbers of sIgG+ and sIgA+ cells with a commensurate increase in sIgM+ B cells, suggesting an in vivo defect in isotype switch. In addition, CVI B cells manifest Ig secretion defects on stimulation with either anti-CD40 and IL-10 or SAC and IL-2 and IL-10, which are of increasing severity for IgM, IgG, and IgA, respectively. These Ig secretion defects are not overcome by addition of a variety of cytokines, including TGF-beta, to anti-CD40-driven cultures. In further studies we show that despite the above abnormalities, CVI B cells are induced to express normal or near-normal levels of C mu, C gamma, and C alpha mRNA after 7 days of stimulation with anti-CD40 and IL-10. That this CH mRNA expression represents a recovery of CVI B cell differentiation is supported by studies of Ig secretion in which CVI B cells that are first stimulated for 7 days with anti-CD40 and IL-10 and then restimulated in coculture with activated normal allogeneic T cells and IL-10, secrete substantial levels of IgM and IgG and increased amounts of IgA. Overall, therefore, CVI B cell function can be significantly improved by maintenance in culture. These data suggest the abnormalities of B cell differentiation in CVI are reversible and that the defect is a form of B cell anergy.

Adult↗
PubMed1994

Treatment of refractory disseminated nontuberculous mycobacterial infection with interferon gamma. A preliminary report.

BACKGROUND: Studies conducted in vitro and in animals suggest that cytokine signals to monocytes or macrophages by interferon gamma are important in the containment and clearance of disseminated nontuberculous mycobacterial infections. METHODS: We studied seven patients with refractory, disseminated nontuberculous mycobacterial infections who were not infected with the human immunodeficiency virus. Three patients were from a family predisposed to the development of Mycobacterium avium complex infections; four patients had idiopathic CD4+ T-lymphocytopenia. Their infections were culture- or biopsy-proved, involved at least two organ systems, and had been treated with the maximal tolerated medical therapy. Cellular proliferation, cytokine production, and phagocyte function were assessed in peripheral-blood cells. Interferon gamma was administered subcutaneously two or three times weekly in a dose of 25 to 50 micrograms per square meter of body-surface area in addition to antimycobacterial medications. Clinical effects were monitored by cultures, biopsies, radiographs, and in one patient a change in the need for paracentesis. RESULTS: In response to phytohemagglutinin, the production of interferon gamma by mononuclear cells from the patients was lower than in normal subjects (P < 0.001), whereas stimulation with ionomycin and phorbol myristate acetate led to normal production of interferon gamma in the patients. Within eight weeks of the start of interferon gamma therapy, all seven patients had marked clinical improvement, with abatement of fever, clearing of many lesions and quiescence of others, radiographic improvement, and a reduction in the need for paracentesis. CONCLUSIONS: Interferon gamma in combination with conventional therapy may be effective for some cases of refractory disseminated nontuberculous mycobacterial infection.

Adult↗
PubMed1994

The B cell-specific transcription factor BSAP regulates B cell proliferation.

The B cell-specific activator protein (BSAP) is a DNA-binding transcription factor expressed in pro-B, pre-B, and mature B cells, but not in plasma cells. In this study, we explored the role of BSAP in B cell function by assessing how the content of this protein varies in cells driven by proliferative stimuli and, conversely, how artificial manipulation of BSAP activity affects cell proliferation. We found that BSAP activity of nuclear extracts increased when B cells were activated by mitogen (lipopolysaccharide [LPS]), antigen receptor-mediated signaling (surface immunoglobulin D [IgD] cross-linking) or T cell-dependent stimulation (CD40 cross-linking). We could suppress BSAP activity by exposure of B cells to phosphorothioate oligonucleotides antisense to the BSAP translation initiation start site, whereas control oligonucleotides were virtually inactive. Antisense-induced BSAP suppression was associated with a striking reduction in LPS-induced proliferation of splenic B cells and in the spontaneous proliferation of B lymphoma cells (CH12.LX), but the antisense oligonucleotide had virtually no effect on proliferation of two cell lines lacking BSAP: the T lymphoma line EL-4 and the plasma cell line MOPC-315. Overexpression of BSAP in splenic B cells or de novo expression in MOPC-315 plasma cells induced by transfection of a BSAP expression plasmid stimulated cell proliferation. Taken together, these results suggest that BSAP activity is a rate-limiting regulator of B cell proliferation. We also found that treatment with the antisense BSAP oligonucleotide downregulated Ig class switching induced by interleukin 4 plus LPS. This effect may be secondary to reduced proliferation or could be mediated through BSAP binding sites in the IgH locus.

Animals↗
PubMed1993

Predominant role of tumor necrosis factor-alpha in human monocyte IL-10 synthesis.

In previous studies it has been shown that the bacterial endotoxin LPS induces an initial burst of inflammatory cytokine synthesis in human monocytes, which is followed by substantial IL-10 production; the IL-10 then down-regulates the inflammatory cytokine production as well as IL-10 production itself. Herein we tested the hypothesis that IL-10 production in human monocytes is under control of one of the cytokines induced by LPS. Accordingly, we cocultured purified human peripheral blood monocytes with a panel of cytokines including TNF-alpha, IL-1 alpha, IL-1 beta, IL-6, granulocyte macrophage-CSF, transforming growth factor-beta, and IFN-alpha and then measured IL-10 mRNA production using a semiquantitative reverse transcription-polymerase chain reaction technique. We found that TNF-alpha had a major effect on IL-10 mRNA production, inducing a 20- to 120-fold increase over baseline production. In contrast, IL-1 alpha, IL-1 beta, IL-6, granulocyte macrophage-CSF, transforming growth factor-beta, and IFN-alpha had little effect (< 3-fold). The induction of IL-10 mRNA by TNF-alpha in monocytes was dose dependent and began between 8 and 24 h after the addition of TNF-alpha; this suggests that the increased IL-10 mRNA level was due to de novo mRNA synthesis rather than mRNA stabilization; this latter finding was corroborated by actinomycin-D time course studies, which showed that the half-life of IL-10 was less than 1 h and was not significantly altered by TNF-alpha. These studies concerning IL-10 mRNA induction by TNF-alpha were corroborated by studies of IL-10 protein secretion: TNF-alpha alone, but not IL-1 alpha, IL-1 beta, or IL-6 induces substantial IL-10 secretion. Furthermore, LPS induces a large amount of IL-10 secretion that is largely inhibited (50 to 75%) by anti-TNF-alpha but not by antibodies to other inflammatory cytokines. Finally, TNF-alpha augments LPS-induced IL-10 secretion. Taken together, these findings suggest that TNF-alpha is unique among the inflammatory cytokines in its role as an inducer of IL-10 in human monocytes, as such, it induces a molecule that provides negative feedback to its own production.

Base Sequence↗
PubMed1993

Regulation of C gamma subclass germ-line transcripts in human peripheral blood B cells.

In the present study we investigated the early steps of human IgG subclass differentiation by defining the conditions necessary for IgG subclass-specific production of germ-line transcripts in human peripheral blood B cells. Constant region of gamma-globulin (C gamma) subclass germ-line transcripts were measured using newly developed reverse transcription and polymerase chain reaction (RT-PCR) assays that were shown to be C gamma subclass-specific germ-line transcripts by size of the amplification products obtained before and after digestion with appropriate endonucleases (NarI and NcoI). In initial studies we found that C gamma 1 and C gamma 2 germ-line transcripts were constitutively expressed in total peripheral blood B cells, but not in high density sIgM+(sIgG-) B cells prepared with Percoll density gradients and magnetic beads separation techniques; the latter cells were therefore used throughout this study. Induction of germ-line transcripts (germ-line C gamma 1 transcript) was noted in stimulated B cells (SAC plus IL-2) at 6 h; thus, the appearance of germ-line transcripts could not be attributed to preferential growth of B cells expressing germ-line transcripts. In subsequent studies we found that induction of germ-line transcripts for the various IgG subclasses fell into two patterns. Induction of C gamma 3 and C gamma 1 germ-line transcripts, transcripts of genes in the first human duplication unit, generally required a proliferative stimulus (Staphylococcus aureus Cowan I, SAC) and was brought about by SAC plus IL-4 (C gamma 3 germ-line transcripts) and SAC alone or SAC plus IL-2 (C gamma 1 germ-line transcripts); in contrast, induction of C gamma 2 and C gamma 4 germ-line transcripts, transcripts of genes in the second duplication unit, was accomplished with cytokines alone: IFN-gamma (C gamma 2 germ-line transcripts) and IL-4 (C gamma 4 germ-line transcripts), and was not augmented by addition of a proliferative stimulus. Finally, we found that IFN-gamma inhibited IL-4-induced C gamma 3 and C gamma 4 germ-line transcripts (with or without SAC). These findings establish that the various human IgG subclasses manifest distinct requirements for the regulation of early steps in isotype differentiation. In addition, they suggest that human C gamma genes exhibit patterns of regulation related to their respective duplication units.

B-Lymphocytes↗
PubMed1993

Effect of downregulation of germline transcripts on immunoglobulin A isotype differentiation.

In this study we determined the role of immunoglobulin (Ig) germline transcripts in the isotype switch differentiation of the cloned lymphoma B cell line CH12.LX. In initial studies, we showed that addition of transforming growth factor beta (TGF-beta) and interleukin 4 (IL-4), either alone or in combination, augment switching from membrane (m)IgM+ to mIgA+ cells, and that increased switching is preceded and paralleled by an increase in the steady-state level of alpha germline transcripts (alpha GLT). Interestingly, TGF-beta and IL-4 affect switching in different ways, as shown by the fact that IL-4 increases and TGF-beta decreases the number of dual-positive (mIgM+/mIgA+) cells; in addition, TGF-beta and IL-4 have different effects on the time course of induction of alpha GLT. In subsequent studies, we established that we could downregulate alpha GLT levels in CH12.LX B cells by transfecting an expression vector that can be induced to produce transcripts antisense to the I alpha exon. Using this approach we downregulated alpha GLT in CH12.LX B cells undergoing switching in the presence of TGF-beta and IL-4 and showed that such downregulation led to decreased switching, as evidenced by decreased appearance of dual-positive B cells as well as decreased IgA synthesis relative to IgM synthesis. This result was corroborated by the fact that incubation of CH12.LX cells with phosphorothio-oligo antisense DNA to I alpha sequence also led to a decrease in the number of dual-positive cells and in the IgA/IgM secretion ratio. In summary, IgA isotype differentiation in CH12.LX B cell, particularly the steps necessary for the elaboration of mIgM+/mIgA+ switch intermediate cells, is inhibited by downregulation of alpha GLT; it is therefore apparent that alpha GLT plays a key role in the initial stage of isotype switch differentiation.

B-Lymphocytes↗
PubMed1993

Functional abnormalities of CD8+ T cells define a unique subset of patients with common variable immunodeficiency.

A substantial subgroup of patients with common variable immunodeficiency (CVI) exhibit an abnormal T-cell phenotype characterized by a low CD4/CD8 ratio associated with a significant increase in the absolute number of CD8+ T cells (CVI4/8low patients). In the present study, we examined the phenotypic and functional properties of purified T-cell subsets in this group of CVI patients. CD8+ T cells from CVI4/8low patients manifested increased expression of HLA-DR and CD57 and decreased expression of CD45RA as compared with CD8+ T cells from normal controls. When stimulated with anti-CD3 and phorbol 12-myristate 13-acetate, purified patient CD8+ T cells exhibited significantly decreased proliferation, c-myc expression, and interleukin-2 (IL-2) production compared with that of normal CD8+ T cells. Nevertheless, mitogen-activated patient CD8+ T cells secreted elevated amounts of gamma-interferon and IL-5 and normal amounts of IL-4. This abnormal pattern of proliferation and cytokine production was limited to the CD8+ T-cell subset as CD4+ T cells from these patients exhibited normal proliferation and cytokine production. In further functional studies, purified CD8+ T cells from CVI4/8low patients manifested increased cytotoxic T-lymphocyte activity and suppressor activity, as compared with normal CD8+ T cells, when they were tested in (1) an anti-CD3 "redirected" cytotoxicity assay and (2) a suppressor assay consisting of CD8+ T cells and Staphylococcus aureus Cowan I (SAC) plus IL-2-stimulated normal (allogeneic) B cells. In the latter case, patient CD8+ T cells suppressed IgG production, but not IgM production. Finally, in studies to evaluate the role of patient CD8+ T cells in the pathogenesis of hypogammaglobulinemia, we determined the capacity of SAC and IL-2 to induce Ig production in highly purified patient B cells, ie, in the absence of patient CD8+ T cells. We found that, whereas B cells from one patient produced normal amounts of IgG, B cells from three patients were unable to produce normal amounts of IgG under these conditions. These data establish the phenotypic and functional characteristics of CD8+ T cells in CVI4/8low and clearly distinguish CVI4/8low patients from other patients with this syndrome. The data do not support the contention that hypogammaglobulinemia in CVI4/8low patients is due to a direct effect of CD8+ T cells on terminal B-cell differentiation, except in the occasional patient. The abnormal CD8+ T cells may, nevertheless, have more subtle effects of lymphoid function that play a role in disease pathogenesis.

Antibody Formation↗
PubMed1993

NIH conference. New insights into common variable immunodeficiency.

Common variable immunodeficiency (CVI) is a heterogenous immunodeficiency syndrome characterized by hypogammaglobulinemia, recurrent bacterial infections, and various immunologic abnormalities. In addition to recurrent infections, patients with this syndrome also have an increased incidence of autoimmune disease and malignancy. Because the spectrum of associated diseases is broad, patients with CVI are seen by various medical specialists. This review discusses the pathogenesis, clinical manifestations, diagnosis, and treatment of CVI.

B-Lymphocytes↗
PubMed1993

Molecular analysis of double isotype expression in IgA switching.

In this and previous studies we have shown that during the course of B cell isotype differentiation occurring in the CH12.LX B cell line, small numbers of cells appear that bear both membrane (m)IgM and membrane IgA. We have cloned relatively stable populations of such dual-bearing cells and have performed studies to determine their molecular status. In the study of one such subclone (CH12.LX.7.10), we show by primer extension that both mu and alpha mRNA contain identical VHDJH gene segments. In complementary studies of another such subclone (CH12.LX.7.13), we show using DNA restriction fragment analysis, that the C mu gene segment, but not the C alpha gene segment, is associated with the JH gene segment. Additionally, Northern blot analysis of productive message of this clone shows that both mu and alpha mRNA cohybridize to the same VH region-specific probe. Taken together, these data suggest that CH12.LX mIgM/mIgA dual-bearing cells occur in the absence of C mu gene segment deletion and that the mu and alpha mRNA transcripts are derived using an alternative mechanism such as transplicing or alternative splicing of a long RNA transcript. On the assumption that these clones are representative of mIgM/mIgA dual-bearing cells appearing during CH12.LX IgM to IgA isotype differentiation, these data support the idea that B cells simultaneously produce mu and alpha mRNA transcripts during one stage of IgA isotype switching.

Animals↗
PubMed1993

Reduced interleukin-2 (IL-2) production in common variable immunodeficiency is due to a primary abnormality of CD4+ T cell differentiation.

Common variable immunodeficiency (CVI) is a condition characterized by hypogammaglobulinemia and impaired antibody responses, resulting in recurrent bacterial infections in untreated patients. In addition, affected individuals exhibit an increased incidence of autoimmunity, malignancy, and certain viral infections, suggesting the presence of an underlying generalized immune dysregulation. We have previously described a subgroup of CVI patients in whom T cells within PBMC populations exhibit a selective defect in lymphokine production. IL-2, IL-4, and IL-5 mRNA production was impaired in these patients, while proliferation, IL-2R expression, and c-myc mRNA production were normal. In the present series of experiments, using highly purified CD4+ T cells prepared by negative selection, we show that this lymphokine production defect is a primary abnormality of CVI CD4+ T cells: whereas CD4+ T cells from CVI patients proliferate normally in response to stimulation by PHA, staphylococcal enterotoxin B (SEB), or anti-CD2 antibodies, these stimuli induce significantly less IL-2 production than observed with CD4+ T cells from normal individuals. Furthermore, we show that this IL-2 production defect is not due to an accessory cell abnormality, since it was seen in the presence of normal (allogeneic) accessory cells, and patient accessory cells supported normal amounts of IL-2 production by PHA-stimulated CD4+ T cells obtained from normal individuals. Of interest, we also found that while IL-2 production by CD4+ T cells from CVI patients induced by stimulation with immobilized anti-CD3 antibody was reduced compared to CD4+ T cells from normal control individuals, this reduction was not statistically significant. Furthermore, stimulation of both CVI patient and normal CD4+ T cells with either ionomycin+phorbol myristate acetate or a combination of immobilized anti-CD3 antibody plus anti-CD28 antibody resulted in a 50-fold increase in IL-2 production compared to stimulation with immobilized anti-CD3 antibody alone, and, under these conditions, CVI and normal CD4+ T cells produced equivalent amounts of IL-2. Finally, minor defects in interferon-gamma production by CD4+ T cells from CVI donors were observed, but these were less severe than the IL-2 production defects and were not statistically significant. We conclude that a primary abnormality of lymphokine production exists in the CD4+ T cells of a subset of patients with CVI.(ABSTRACT TRUNCATED AT 400 WORDS)

Antibodies, Monoclonal↗
PubMed1993

Lymphocyte phenotype and function in the chronic fatigue syndrome.

Lymphocytes of 18 patients meeting the Centers for Disease Control (CDC) case definition for the chronic fatigue syndrome (CFS), 10 similar, chronically fatigued patients not fully conforming to the CDC case definition, and 17 matched, healthy individuals were studied to determine the presence of abnormalities of peripheral cell phenotype and function. Extensive phenotypic analyses of B- and T-cell subsets, natural killer (NK) cells, and macrophages were performed using single-, dual-, and three-color flow cytometry. Compared to controls, in CFS patients the percentage of CD4 T cells and CD4,CD45RA, or naive T cells, was reduced. The CD4,CD45RO, or memory T-cell, subset was numerically normal but expressed increased levels of adhesion markers (CD29, CD54, and CD58). CFS patient lymphocytes showed reduced proliferative responses to phytohemagglutinin, concanavalin A, and staphylococcal enterotoxin B. Lymphocytes from fatigue patients not meeting the CDC definition showed similar abnormalities. These data indicate that peripheral T cells manifest an increased state of differentiation in CFS and related conditions. This may arise as a consequence of an underlying neuropsychiatric and/or neuroendocrine disorder or because of exposure to antigens or superantigens of an infectious agent.

Adolescent↗
PubMed1993

Quantitative measurement of human T-cell receptor V beta subfamilies by reverse transcription-polymerase chain reaction using synthetic internal mRNA standards.

Quantitative determination of T-cell receptor (TCR) V beta expression is necessary to define the changes in TCR-V beta subfamily expression that occur during T-cell maturation and selection and to detect alterations of the TCR-V beta repertoire that may be associated with human diseases. Here we describe and validate a quantitative reverse transcription-polymerase chain reaction (RT-PCR) technique to determine human TCR-V beta subfamily mRNA levels (as well as other mRNA species), based on the use of synthetic poly(A) mRNA internal standards that are coprocessed with native (sample) mRNA transcripts. The technique allows simultaneous reverse transcription of sample and standard mRNA and thus obviates errors arising during reverse transcription. In addition, the technique allows coamplification of several concentrations of standard mRNA (cDNA) with sample mRNA (cDNA) under conditions in which these mRNAs amplify with equal efficiency; thus, it avoids errors resulting from saturation of competition effects. Finally, the technique is sensitive to lower than 1.5-fold differences in input mRNA. To apply the technique, we also describe methods for the generation of poly(A) mRNA internal standards that can be used to quantitate TCR-V beta 2/6/7 and TCR-C beta mRNA.

Antigens, Bacterial↗
PubMed1993

T-cell abnormalities in common variable immunodeficiency.

Common variable immunodeficiency (CVI) is a heterogeneous condition marked by a number of different immunologic defects. One group of patients, perhaps 60% of the CVI group as a whole, is characterized by T cells that produce reduced amounts of IL-2 (mRNA and protein product), IL-4, and IL-5 (mRNA) when stimulated with phytohemagglutinin. This defect does not extend to all lymphokines, however, because the cells produce normal amounts of interferon-gamma (mRNA and protein product) when exogenous IL-2 is present. Recently, we have reexamined the T cell lymphokine production defect using a panoply of T-cell activation stimuli and have shown that the defect is a subtle one that depends on activation of the cell via the CD3-T-cell receptor complex. Because T cells proliferate normally when stimulated via this receptor, this finding suggests the presence of a "downstream" defect, perhaps one involving the factors that are necessary for activation of lymphokine genes. A second form of CVI, in this case involving approximately 30% of the CVI group as a whole, is characterized by a reduced CD4/CD8 ratio and elevated numbers of CD8+ T cells bearing the CD57 marker. Although the CD4+ T cells in this patient group elaborate normal amounts of IL-2 under various activation conditions, their CD8+ T cells produce increased amounts of interferon-gamma. Furthermore, the CD8+ T cells in this case act as "suppressor" T cells, which suppress IgG production but not IgM production of purified (normal) SAC+, IL-2-induced B cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, CD↗
PubMed1992

Effect of transforming growth factor (TGF)-beta 1 on IgA isotype expression. TGF-beta 1 induces a small increase in sIgA+ B cells regardless of the method of B cell activation.

Transforming growth factor-beta (TGF-beta) has been reported to play an important role in IgA isotype expression when B cells are stimulated with LPS. The goal of the present study was to determine whether TGF-beta has similar effects on IgA isotype expression under more physiologic conditions utilizing a variety of B cell activation systems. As previously reported, in the LPS system TGF-beta caused a small, but significant, absolute increase in surface IgA (sIgA) expression and a very definite increase in IgA secretion; these effects were enhanced by IL-2 and IL-5. In the case of B cell stimulation with another B cell stimulant, the thymus-independent type II mitogen, anti-IgD-dextran, TGF-beta led to a similar small increase in sIgA expression, but caused suppression of IgA secretion. Using the Th2 cell clones CDC35 and D10 to stimulate resting B cells in a cognate and non-cognate T cell-dependent fashion, respectively, TGF-beta again increased sIgA expression to a similar small extent. TGF-beta at low doses (0.1 ng/ml) did not increase IgA secretion significantly and, at higher doses (1.0 ng/ml) caused significant suppression of IgA secretion. Addition of various cytokines (IL-2, -4, -5, D10sup) other than TGF-beta to stimulated B cells did not increase sIgA expression, but did give rise to increased amounts of IgA secretion, especially when activated D10 T cells were used as the B cell stimulant. Finally, the addition of an antibody against TGF-beta to cultures containing TGF-beta on day 2 led to partial or complete reversal of the inhibitory effects of TGF-beta on IgA secretion. In conclusion, TGF-beta causes a consistent, but small increase in sIgA+ B cells, in cultures of B cells stimulated by a variety of T cell-dependent or independent stimuli. In contrast, TGF-beta either promotes or inhibits B cell survival and IgA secretion, depending on the method of B cell activation. These results are most consistent with the view that TGF-beta provides only a partial or incomplete IgA switch signal but that additional factors are involved in IgA isotype switching and differentiation.

Animals↗