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Biomedical subjects

R S Geha

Publications and source records attributed to R S Geha.

At least 127 records · Page 7Linked to original sources
PubMed1991

Lymphokine profile in bone marrow transplant recipients.

Immune reconstitution after bone marrow transplantation (BMT) recapitulates immune ontogeny. At birth there is an imbalance in lymphokine production, with decreased production of interferon-gamma (IFN-gamma) compared with interleukin-4 (IL-4) and IL-2. We investigated whether a similar imbalance in lymphokine production occurs in BMT recipients within 6 months after transplantation. Our results show that BMT recipients not treated with immunosuppressive drugs have a decrease in IFN-gamma production and IL-2, in comparison with IL-4. This imbalance was likely to result from impaired signal transduction through surface receptors, because it was detectable on stimulation with Concanavalin A (ConA), but was overcome completely or largely by stimulation with phorbol myristate acetate (PMA) + ionophore, which bypass surface receptors and mimic the effects of second messengers. In contrast, lymphokine production in patients treated with immunosuppressive drugs (cyclosporine A, corticosteroids) was abnormal after stimulation with PMA and ionophore, as well as ConA. Thus, treated BMT recipients exhibit an additional deficit, which affects the signaling cascade down-stream of second messenger generation and results in impaired lymphokine production.

Adult↗
PubMed1991

Deletional switch recombination occurs in interleukin-4-induced isotype switching to IgE expression by human B cells.

There is controversy as to whether deletional rearrangement occurs between the IgM and IgE switch regions (S mu and S epsilon, respectively) during switching to the IgE isotype. We have addressed the issue by stimulating normal human B cells, sorted for lack of expression of surface IgE, to produce IgE by infection with Epstein-Barr virus (EBV) in the presence of interleukin 4 (IL-4). Genomic DNA was amplified for S mu/S epsilon switch junction fragments by utilizing the nested-primer polymerase chain reaction. Switch junction fragments were amplified from B cells infected with EBV in the presence of IL-4 but not from B cells infected with EBV alone. The DNA sequence of these "switch fragments" revealed direct joining of S mu to S epsilon in each case. The recombination sites within S mu were clustered within 900 base pairs at the 5' end of the switch region, suggesting that there are "hot spots" for recombination within S mu. The S epsilon recombination sites were scattered throughout the S epsilon region. These findings indicate that IL-4-induced isotype switching to IgE production in human B cells is accompanied by DNA rearrangements with joining of S mu to S epsilon.

B-Lymphocytes↗
PubMed1991

Staphylococcal exotoxins deliver activation signals to human T-cell clones via major histocompatibility complex class II molecules.

We investigated whether staphylococcal exotoxins (SEs), in addition to their capacity to induce T-cell activation restricted by the T-cell receptor (TCR) beta-chain variable region, can deliver an activation signal to human T-cell clones through major histocompatibility complex (MHC) class II molecules. Eleven human T-cell clones (9 alpha beta TCR and 2 gamma delta TCR clones) of different antigenic specificities were tested for their capacity to proliferate in response to toxic shock syndrome toxin 1 (TSST-1) and two SEs, SEA and SEB. In the absence of accessory cells, only 4 alpha beta TCR clones were stimulated to proliferate, each by a single SE, and to mobilize intracellular free Ca2+ in response to that SE, events indicative of TCR engagement and, presumably, recognition restricted by the beta-chain variable region. In the presence of accessory cells, each of the 11 T-cell clones was stimulated to proliferate by any one of the three SEs tested. This apparently TCR-unrestricted SE-mediated polyclonal proliferation of T-cell clones occurred in the absence of an increase in intracellular free Ca2+ and was not dependent on the presence of MHC class II expression on accessory cells. In contrast, SE-mediated polyclonal proliferation did not occur in 3 alpha beta TCR clones derived from an MHC class II-deficient patient. Furthermore, all of the three SEs induced the proliferation of 4 natural-killer-cell clones, suggesting that expression of TCR/CD3 complex is not essential for SE-mediated polyclonal proliferation of activated lymphocytes. These results indicate that MHC class II molecules transduce activation signals to human T- and natural-killer-cell clones.

Bacterial Toxins↗
PubMed1991

Hydrocortisone and IL-4 induce IgE isotype switching in human B cells.

Induction of IgE synthesis in human B cells requires two signals. The first signal is delivered by the cytokine IL-4. The second signal activates B cells and is delivered by T cells, EBV infection, or engagement of the B cell-specific Ag CD40. Hydrocortisone (HC) has recently been shown to synergize with IL-4 to induce IgE synthesis in CD5+ chronic lymphocytic leukemia B cells. We show herein that a combination of HC and rIL-4 induces IgE synthesis in highly purified normal peripheral blood B cells. HC and IL-4 acted directly on B cells, because T cells and monocytes were not required for IgE synthesis. IgE induction was shown to occur in surface IgE- B cells isolated by cell sorting. These results suggest that IgE synthesis results from isotype switching, rather than from expansion of a precommitted B cell population. Furthermore, IgE synthesis was induced in sorted CD5- B cells, indicating that the ability to produce IgE in response to HC and IL-4 is not constrained by CD5 expression. Endogenous IL-6 was critical for induction of IgE synthesis by HC and IL-4, because an anti-IL-6 antibody strongly inhibited IgE production. These data suggest that hormones may play an important role in the regulation of IgE synthesis.

Antigens, CD↗
PubMed1991

Engagement of CD14 on human monocytes terminates T cell proliferation by delivering a negative signal to T cells.

We have recently shown that engagement of the human monocytic Ag CD14 by murine mAb induces lymphocyte function-associated antigen-1/intercellular adhesion molecule-1-dependent homotypic adhesion. To determine whether CD14 plays a role in monocyte-T cell interactions, we tested the effect of anti-CD14 mAb on the proliferation of human T cells. Our results show that anti-CD14 mAb strongly inhibited T cell proliferation induced by Ag, anti-CD3 mAb, and mitogenic lectins. Inhibition by anti-CD14 mAb was epitope-dependent and required physical contact between monocytes and T cells. CD14 engagement did not affect IL-2R expression or IL-2 synthesis but induced a state of unresponsiveness that was not IL-2 specific; proliferation of anti-CD3-activated T cell blasts in response to both IL-2 and IL-4 was abrogated by addition of monocytes preincubated with anti-CD14 mAb. Inhibition of T cell proliferation after engagement of CD14 on monocytes was likely to result from delivery of a negative signal to T cells, rather than from disruption of a costimulatory monocyte-derived signal, because incubation of monocytes with anti-CD14 mAb also inhibited monocyte-independent T cell proliferation induced by PMA and ionophore. These results, together, point to a role of CD14 in the monocyte-dependent regulation of T cell proliferation.

Adult↗
PubMed1991

Transcriptional activation of IL-1 beta and tumor necrosis factor-alpha genes by MHC class II ligands.

Ligands that bind MHC class II (Ia) molecules, including staphylococcal exotoxins (SE) and mAb induce IL-1 and TNF secretion in human monocytes and monocytic cell lines. In this study, we have analyzed the mechanisms by which SE induce IL-1 beta and TNF-alpha production. Treatment of human peripheral blood monocytes with staphylococcal exotoxin B and toxic shock syndrome toxin-1 resulted in a biphasic increase of IL-1 beta mRNA that lasted more than 12 h and in a more transient rise in TNF-alpha mRNA. A F(ab) preparation of the anti-HLA DR mAb L243 also caused a significant increase in monokine mRNA levels. Stimulation of a monocytic cell line, THP-1, with staphylococcal exotoxin B and toxic shock syndrome toxin-1 induced a rapid rise in IL-1 beta and TNF-alpha mRNA levels. This response peaked at 1 to 3 h poststimulation and remained detectable at 12 h. Nuclear run-on transcription assays demonstrated that SE cause transcriptional activation of the IL-1 beta and TNF-alpha genes. This transcriptional activation did not require de novo protein synthesis as it was not inhibited by the protein synthesis inhibitor cycloheximide. These results define an important function for Ia molecules as regulators of cytokine gene expression and add to the understanding of the changes in cellular function induced by SE.

Bacterial Toxins↗
PubMed1991

Engagement of MHC-class II molecules by staphylococcal exotoxins delivers a comitogenic signal to human B cells.

The staphylococcal exotoxin toxic shock syndrome toxin-1 (TSST-1) has been demonstrated to bind to monomorphic determinants on MHC-class II molecules. In this study, we have used TSST-1 to probe the role of MHC-class II molecules in the activation and differentiation of resting human B cells. Highly purified B cells were stimulated with TSST-1, alone or in combination with PMA or with anti-human IgM antibodies (anti-mu) and the resulting B cell proliferation and Ig production were monitored. On its own, TSST-1 failed to induce B cell proliferation or Ig production. However, TSST-1 synergized with PMA and with anti-mu in inducing B cell proliferation in the absence of any added T cells or T cell factors. TSST-1 did not induce or potentiate early activation events associated with anti-mu treatment such as phosphoinositide hydrolysis and Ca2+ mobilization. Also, TSST-1 did not potentiate the capacity of anti-mu to induce the transcription of early activation genes such as c-myc. Finally, in contrast to its capacity to promote mitogen-trigered B cell proliferation, TSST-1 failed to induce the differentiation of B lymphocytes into Ig-secreting cells in the absence of added T cells. These results indicate that TSST-1 delivers a comitogenic signal to B cells via MHC-class II molecules that is distinct from signals delivered via surface mu and further strengthens the role of MHC-class II molecules as signal transducing structures.

Antibodies, Anti-Idiotypic↗
PubMed1991

The CD4 molecule is not always required for the T cell response to bacterial enterotoxins.

T cells respond in a V beta-restricted fashion to bacterial enterotoxins bound to major histocompatibility complex (MHC) class II molecules. The requirement for CD4 in MHC class II-restricted T cell responses is very well established. We have assessed the role of CD4 in the T cell response to the bacterial enterotoxins Staphylococcal enterotoxin A (SEA), SEB, and toxic shock syndrome toxin 1. Three CD4- murine T cell hybridomas were transfected with the human CD4 molecule and assayed for interleukin 2 production in the presence of accessory cells bearing human MHC class II molecules and of the appropriate enterotoxin. The results clearly indicate that CD4- cells responded even to suboptimal concentrations of enterotoxin(s) equally well as CD4+ cells. Furthermore, expression of CD4 did not result in the acquisition of previously undetectable reactivity to enterotoxins. These results suggest that unlike the case with antigen-specific responses, formation of a T cell receptor-CD3/CD4 supramolecular complex is not always essential for T cell activation by bacterial enterotoxins.

Animals↗
PubMed1991

Induction of human T cell proliferation by a monoclonal antibody to CD5.

A mouse mAb, TS 43, which recognized the human CD5 molecule, was found to induce the proliferation of human peripheral blood T cells. TS 43 mAb precipitated from 125I-radiolabeled T cells a 67-kDa band, which comigrated with the 67-kDa band precipitated by the anti-CD5 mAb OKT1. Preclearing of cell lysates with OKT1 mAb abolished the capacity of TS 43 mAb to precipitate radiolabeled material from T cell lysates. Furthermore, a mouse T cell hybridoma transfected with human CD5 was stained by TS 43 mAb. T cell proliferation mediated by TS 43 mAb was monocyte dependent, and was accompanied by IL-2R expression and by IL-2 synthesis. T cell activation by TS 43 mAb involved a rise in intracellular calcium level (CA2+)i and was dependent on the expression of the TCR/CD3 complex because no rise in (Ca2+)i was observed in a TCR-beta-deficient Jurkat T cell mutant. This study indicates that CD5 should be added to the list of surface molecules that can signal T cells to proliferate.

Antibodies, Monoclonal↗
PubMed1991

Novel immune deficiencies: defective transcription of lymphokine genes.

A 4-year-old female with severe combined immunodeficiency (SCID) had normal numbers of T cells in circulation and normal T cell subsets. However, her T cells proliferated poorly to mitogens and did not proliferate to antigens or to anti-CD3 mAb. Interleukin-2 (IL-2) receptor expression was normal but IL-2 synthesis was undetectable. The addition of recombinant IL-2 to a mitogen-stimulated culture resulted in normalization of the proliferative response. Northern blot analysis of total RNA derived from the patient's T cells revealed a weak or absent expression of mRNA coding for IL-2, IL-3, IL-4, and IL-5. In contrast, there were normal amounts of mRNA coding for granulocyte-macrophage colony-stimulating factor (GM-CSF). Tumor necrosis factor and IL-6 production was also normal. Nuclear run on transcriptional assays revealed markedly decreased levels of newly initiated nuclear transcripts coding for IL-2, IL-3, IL-4, and IL-5 and normal levels of GM-CSF transcripts in patient relative to control lymphocytes. These results indicate that the patient's T cells suffered from a defect affecting the transcription of multiple T cell lymphokines and suggest that abnormalities affecting the production of T cell lymphokines may underlie some of the primary immunodeficiency diseases.

Bone Marrow Transplantation↗
PubMed1991

Cardiotoxicity during treatment of severe childhood asthma.

We prospectively evaluated 20 patient admissions for severe exacerbation of childhood asthma at The Children's Hospital, Boston, to detect evidence of cardiotoxicity. Evidence of cardiotoxicity was found in all six patient admissions for which isoproterenol infusion was utilized. This included marked elevation of serum creatine phosphokinase isoenzyme (CPK-MB) levels and electrocardiogram abnormalities consistent with transient myocardial ischemia. Peak serum CPK-MB levels were significantly lower and electrocardiogram abnormalities were significantly less frequent during 14 patient admissions for which isoproterenol infusion was not utilized. Risk factors associated with cardiotoxicity included tachycardia, hypercapnia, acidosis, and intravenous isoproterenol therapy. We conclude that cardiotoxicity is not infrequent during therapy for severe exacerbations of childhood asthma. Electrocardiograms and measurement of serum CPK-MB levels are sensitive, useful, and readily obtained indicators of cardiotoxicity. Abnormalities of these studies may detect cardiotoxicity prior to the occurrence of more blatant or catastrophic manifestations of cardiotoxicity. We therefore recommend serial monitoring of serum CPK-MB levels and electrocardiograms for all children requiring an admission to the intensive care unit for management of severe asthmatic exacerbation.

Adolescent↗
PubMed1990

CD40 and IgE: synergism between anti-CD40 monoclonal antibody and interleukin 4 in the induction of IgE synthesis by highly purified human B cells.

A novel pathway of IgE-B cell differentiation has been identified. Engagement of the B cell antigen CD40 by F(ab')2 fragments of monoclonal antibody (mAb) 626.1 in the presence of recombinant interleukin 4 (rIL-4) induced intense IgE synthesis, but modest IgG synthesis, by highly purified human B cells. Surface IgE- B cells isolated by cell sorting were induced to produce IgE by mAb 626.1 and IL-4. Thus, IgE synthesis is unlikely to result from expansion of a B cell population precommitted to IgE in vivo. A neutralizing anti-IL-6 antibody strongly, but not completely, inhibited the IgE response. This indicates that autocrine production of IL-6 plays an important amplification role in IgE synthesis triggered by anti-CD40 mAb and IL-4. Although the exact role played by CD40 in IgE responses in vivo remains to be established, this T cell-independent system represents a useful model to characterize the biochemical and molecular events leading to IgE synthesis in human B cells.

Antibodies, Monoclonal↗