Molecular analysis of the induction of immunoglobulin E synthesis in human B cells by interleukin 4 and engagement of CD40 antigen.

The molecular events leading to immunoglobulin E (IgE) synthesis in human sIgE- B cells stimulated with interleukin 4 (IL-4) and anti-CD40 monoclonal antibody (mAb) 626.1 were analyzed. Anti-CD40 mAb increased the levels of IL-4-induced germline C epsilon transcripts and induced the production of mature C epsilon mRNA.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Primary combined immunodeficiency resulting from defective transcription of multiple T-cell lymphokine genes.

The circulating T lymphocytes of a female child with recurrent opportunistic infections were normal in number and phenotype but exhibited poor proliferation and decreased synthesis of the T-cell growth factor interleukin (IL) 2 in response to mitogens. Recombinant IL-2 fully restored the proliferative responses of her T cells, suggesting that her poor immune function was related to IL-2 deficiency. Northern blot analysis of total cellular RNA from the patient's T cells revealed markedly decreased levels of IL-2 mRNA of normal size.

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.

Induction of germ-line and mature C epsilon transcripts in human B cells stimulated with rIL-4 and EBV.

EBV and rIL-4 induce T cell-independent IgE production by normal human B cells. We demonstrate here that EBV and IL-4 induced the synthesis of IgE by surface IgE-negative B cell precursors isolated by cell sorting. This result suggests that the induction of IgE by EBV and IL-4 results not merely from the expansion of a precommitted surface IgE-positive B cell population but more likely from IL-4-directed switching to IgE.

Engagement of major histocompatibility complex class II molecules induces sustained, lymphocyte function-associated molecule 1-dependent cell adhesion.

Antigenic stimulation is associated with enhanced adhesion between T cells and antigen-presenting cells (APC). Binding of ligands to the T cell antigen receptor activates the adhesion function of lymphocyte function-associated molecule 1 (LFA-1; CD11a/CD18). We demonstrate here that ligand binding to major histocompatibility complex class II (Ia) molecules also activates LFA-1 function, providing a reciprocal mechanism for the induction of adhesion between T cells and Ia+ APC.

Interleukin 4 down-regulates the expression of CD14 in normal human monocytes.

Recombinant interleukin 4 (IL4) down-regulates the expression of CD14 on normal human monocytes, as assessed by flow cytometry, binding assays with radiolabeled anti-CD14 monoclonal antibody (mAb), and immunoprecipitation of 125I-labeled monocytes with anti-CD14 mAb. In parallel, CD23 expression on monocytes was strongly increased by IL4 stimulation, as assessed by both flow cytometry and immunoprecipitation. Down-regulation of surface CD14 was first detectable after 24-36 h of incubation with rIL4, and was almost complete after 4 days of culture.

Binding of toxic shock syndrome toxin-1 to murine major histocompatibility complex class II molecules.

The staphylococcal exotoxin toxic shock syndrome toxin-1 (TSST-1) has potent stimulatory effects on murine and human lymphocytes. This is the consequence of TSST-1 binding to major histocompatibility complex (MHC) class II molecules and the engagement in a V beta-restricted fashion of the T cell receptor by the TSST-1-MHC class II complex. Using radioligand and functional assays we have recently shown that TSST-1 binds to all HLA-DR (n = 14), HLA-DQ (n = 2) and HLA-DP (n = 2) phenotypes tested.

Engagement of the monocyte surface antigen CD14 induces lymphocyte function-associated antigen-1/intercellular adhesion molecule-1-dependent homotypic adhesion.

Murine anti-CD14 mAb which recognize different CD14 epitopes induced marked homotypic adhesion of normal human monocytes. Induction of aggregation by anti-CD14 mAb required Mg2+, occurred at an optimal temperature of 37 degrees C, but not at 4 degrees C, and exhibited a kinetics which differed from adhesion triggered by IFN-gamma and anti-CD43 mAb. Monocyte adhesion induced by anti-CD14 mAb required neither Fcy gamma R engagement nor cross-linking of CD14, because adhesion was induced by F(ab)'2 fragments, as well as by monovalent F(ab) fragments of anti-CD14 mAb.

The alpha 1 domain of the HLA-DR molecule is essential for high-affinity binding of the toxic shock syndrome toxin-1.

Several exoproteins from the bacterium Staphylococcus aureus are highly potent polyclonal activators of T cells in the presence of cells bearing class II antigens of the major histocompatibility complex (MHC). These toxins, including the toxic shock syndrome toxin (TSST-1), act at nanomolar concentrations, bind directly to class II molecules, and do not require the processing typical of nominal antigen. Each toxin is capable of stimulating a subpopulation of peripheral T lymphocytes bearing particular V beta sequences as part of their alpha beta T-cell receptors.