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E S Vitetta

Publications and source records attributed to E S Vitetta.

At least 127 records · Page 7Linked to original sources
PubMed1990

A soluble, high-affinity, interleukin-4-binding protein is present in the biological fluids of mice.

Cytokines such as interleukin 4 (IL-4) play a key role in the regulation of immune responses, but little is known about how their multiple activities are regulated in vivo. In this report, we demonstrated that an IL-4-binding protein (IL-4BP) is constitutively present in the biological fluids of mice (serum, ascites, fluid, and urine). Binding of 125I-labeled IL-4 to the IL-4BP is specific and saturable and can be inhibited by an excess of unlabeled IL-4 but not IL-2. The IL-4BP binds IL-4 with an affinity similar to that reported for the cellular IL-4 receptor (Kd approximately 7 x 10(-11) M) and has a molecular mass of 30-40 kDa and pI values of 3.6-4.8. IL-4BP-containing biological fluids or purified IL-4BP competitively inhibit the binding of 125I-labeled IL-4 to mouse T or B cells and inhibit the biological activity of IL-4 but not IL-2. The serum levels of IL-4BP in severe combined immunodeficiency (SCID) mice are lower than those of normal mice. The above findings suggest that IL-4BP plays an important immunoregulatory role in vivo.

Animals↗
PubMed1990

Immunoconjugates containing ricin A chain and either human anti-gp41 or CD4 kill H9 cells infected with different isolates of HIV, but do not inhibit normal T or B cell function.

We have previously reported that immunoconjugates composed of deglycosylated ricin A chain coupled to either recombinant (r) CD4 or two different monoclonal human anti-gp41 antibodies (rCD4-dgA and anti-gp41-dgA, respectively) are specifically toxic to HIV-infected lines of human T cells (H9) and monocytes (U937). In order to further evaluate these immunoconjugates as potential therapeutic reagents for killing HIV-infected cells, H9 cells infected with five different isolates of HIV were used as target cells in vitro. All three HIV-specific immunoconjugates were toxic to H9 cells infected with each HIV isolate, but were virtually nontoxic to uninfected cells. Chloroquine markedly potentiated the specific toxicity of all three conjugates, particularly the anti-gp41-dgAs. None of the conjugates affected the ability of normal peripheral blood B cells to respond to mitogen or the ability of normal T cells to respond to alloantigens.

Antibodies, Monoclonal↗
PubMed1989

IL-4 induces the specific rearrangement of gamma 1 genes on the expressed and unexpressed chromosomes of lipopolysaccharide-activated normal murine B cells.

Small, resting, surface IgM+/surface IgD+ murine B cells undergo an Ig class switch to IgG1 or IgE after stimulation with LPS and T cell supernatants containing IL-4. To firmly establish the role of IL-4 in the directed switch recombination observed in IgG1-secreting cells, we have 1) used highly purified native IL-4 instead of T cell supernatants, 2) used resting B cells from F1 mice in which the active IgH allele was determined before culture, 3) taken advantage of the allelic differences in the restriction fragment lengths of mu, gamma 1, gamma 2b, and gamma 3 loci to determine the status of the CH genes on both the expressed and unexpressed chromosomes, and 4) used different restriction enzymes to distinguish between deletion and rearrangement of a given CH gene. Our results indicate that LPS alone induces rearrangement of the gamma 3 genes on both chromosomes whereas stimulation with LPS plus IL-4 results in deletion of gamma 3 genes and rearrangement of gamma 1 genes on both chromosomes. The studies definitively establish the role of IL-4 in directed switch recombination to the gamma 1 locus in LPS-stimulated murine B cells.

Animals↗
PubMed1989

In vivo administration of Fab' fragments of anti-L3T4 (GK1.5) antibody inhibits the T helper cell function of murine lymph node cells.

The effect of intravenous injection of Fab' fragments of anti-L3T4 antibody (GK1.5 monoclonal antibody) into mice was studied. This treatment depleted L3T4+ cells from the popliteal lymph nodes of keyhole-limpet hemocyanin-primed mice. The T cells that remained were unable to provide help to antigen-specific B cells in vitro. The results obtained using Fab' fragments were comparable with those using intact anti-L3T4 antibody and demonstrate that either form of GK1.5 is a potentially useful immunosuppressive agent in mice.

Animals↗
PubMed1989

Interactions between receptors for interleukin 2 and interleukin 4 on lines of helper T cells (HT-2) and B lymphoma cells (BCL1).

IL-2 and IL-4 induce a synergistic proliferative response in HT-2 cells, suggesting that IL-2Rs and IL-4Rs may interact. The purpose of this study was to examine the effect of IL-4 on the expression and function of IL-2Rs. Preincubation of HT-2 and BCL1-3B3 cells with IL-4 for 60 min at 4 degrees C or 37 degrees C resulted in a partial decrease in the number, but not the affinity of high affinity IL-2Rs as evidenced by Scatchard analysis of binding data. The decrease in the number of high affinity receptors correlated with decreased internalization of IL-2. After preincubation with IL-4, crosslinking of 125I-IL-2 to high affinity IL-2Rs also demonstrated a approximately 50% reduction in the number of high affinity IL-2Rs. Another lymphokine, IL-1, which acts on HT-2 cells, had no measurable effect on the affinity or number of IL-2Rs. Taken together, these results indicate that IL-4 downregulates the expression of high affinity IL-2Rs on some cells. It is not known whether this occurs by a direct ligand-mediated receptor interaction, by the sharing of a common receptor subunit, or by interaction of the two receptors with another membrane molecule or cytoskeletal component.

B-Lymphocytes↗
PubMed1989

Splenic B cells and antigen-specific B cells process anti-Ig in a similar manner.

B lymphocytes can process and present antigen to T cells. However, the fate of native antigen after its binding to specific B cells, i.e., the intracellular events involved in the processing and recycling of the antigenic fragments to the cell surface for antigen presentation, are not well understood. In the present study, we demonstrate that murine B cells degrade anti-Ig molecules bound to their surface and release acid soluble fragments into the supernatant. We also demonstrate that the kinetics of this process are identical for anti-mu, anti-delta, and anti-light chain antibodies, indicating that both surface IgM and surface IgD are equally effective in binding antigen and directing its processing. We also describe the effects of azide, chloroquine, and irradiation on this process. To extend these studies to the processing of specifically bound antigen, we demonstrate that highly purified trinitrophenyl antigen-binding cells degrade anti-Ig molecules with the same kinetics as unpurified splenic B cells. Thus, this purified population provides a suitable model system for the analysis of antigen degradation by antigen-specific cells.

Animals↗
PubMed1989

Cross-linking of interleukin 4 to surface molecules on murine T and B lymphocytes.

Interleukin 4 (IL-4) is a T-cell derived lymphokine with multiple activities on a variety of cells. An intriguing feature of the different IL-4-mediated activities is their requirements for markedly different concentrations of IL-4 even on the same cell population. To gain some insight into the phenomenon, we have analyzed the structure of IL-4-binding proteins on T and B cells by cross-linking different concentrations of 125I-labeled IL-4 (125I-IL-4) to cells. Cross-linking of 125I-IL-4 at relatively low concentrations in the presence of the cross-linking agent 3,3'-dithiobis(propionic acid hydroxysuccinimide ester) resulted in the detection of the previously described 60- to 75-kDa protein. At higher 125I-IL-4 concentrations, however, an additional molecule of 105 kDa was observed. Cross-linking of 125I-IL-4 to both molecules was specific; it was inhibited by the presence of a 50-fold excess of either unlabeled IL-4 or monoclonal anti-IL-4 antibody. Furthermore, considerable size heterogeneity of the IL-4-binding proteins was evident in different cell populations. These results suggest that IL-4 receptors might have a more complex structure than originally reported and/or that high concentrations of IL-4 might induce interactions of the previously described IL-4 receptor (60-75 kDa) with a 105-kDa molecule. Hence, it is possible that IL-4 might generate a different signal at high concentrations through interaction of its receptor with another membrane molecule.

Animals↗
PubMed1989

Human immunodeficiency virus-infected T cells and monocytes are killed by monoclonal human anti-gp41 antibodies coupled to ricin A chain.

Two human monoclonal antibodies specific for the envelope glycoprotein (gp), gp41, of the human immunodeficiency virus were conjugated to deglycosylated ricin A chain. These immunotoxins killed human immunodeficiency virus-infected H9 (T cell) and U937 (monocyte) cell lines but were nontoxic to the uninfected cell lines or to class II-positive Daudi cells. Specific killing of infected H9 cells could be completely blocked by recombinant gp160 and partially blocked by unconjugated anti-gp41 antibody but was not blocked by recombinant gp120 or human IgG demonstrating specificity for gp41. The specific toxicity of the immunotoxins for infected U937 cells was markedly potentiated by chloroquine.

Antibodies, Monoclonal↗
PubMed1989

Synthesis of germ-line gamma 1 immunoglobulin heavy-chain transcripts in resting B cells: induction by interleukin 4 and inhibition by interferon gamma.

Interleukin 4 (IL-4) induces the expression of IgG1 and IgE in lipopolysaccharide-stimulated B cells. Previous studies have suggested that heavy-chain class switching may be regulated by increasing the accessibility of specific switch regions to switch recombinases. In this study, we have used an RNase protection assay to demonstrate that IL-4 induces expression of germ-line gamma 1 transcripts in B cells within 4 hr of culture; induction is dose-dependent and is inhibited by interferon gamma. IL-4 alone is capable of inducing the expression of germ-line gamma 1 transcripts in small, resting B cells, but lipopolysaccharide enhances expression. The germ-line transcripts are the same size (1.8 and 3.4 kilobases) as the secreted and membrane forms of the functional gamma 1 mRNAs and presumably result from the splicing of an upstream switch-region exon(s) to the gamma 1 constant-region exon(s). These data strongly support the "accessibility" model for the regulation of isotype switching and suggest that lymphokines such as IL-4 may direct specific switch events by transcriptional activation of the corresponding switch regions.

Animals↗
PubMed1989

The processing of antigen and anti-Ig by antigen-specific B cells.

B lymphocytes are very efficient antigen-presenting cells when they bear surface receptors for the antigen in question. However, there is very little known about the intracellular events occurring between the time B cells bind native antigen and present it in processed form to T cells. To analyze internalization and degradation of antigen versus anti-Ig or anti-MHC antibodies by B cells, we have used highly purified resting antigen-specific B lymphocytes that bind the hapten, trinitrophenyl. These cells were treated with [125I]-labeled trinitrophenylated antigens or with [125I]-labeled antibodies reactive with either cell surface immunoglobulin or major histocompatibility complex (MHC) (class I or class II) molecules. The fate of these proteins was followed by measuring the amount of acid soluble and insoluble radioactivity associated with the cells or released into the incubation medium. The cell-associated and released radioactivity was further analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Our results demonstrate that the kinetics of degradation of specific antigen into acid soluble fragments which are released into the culture medium closely parallel those with which B cells acquire the ability to specifically conjugate to carrier-specific T cells. In contrast, degradation of anti-Ig is more complete than the degradation of antigen but requires a longer period of time to reach completion. Furthermore, the initial release of soluble fragments of anti-Ig as compared to antigen into the culture medium is marginally slower. Finally, there is significant intracellular accumulation of degradation intermediates when anti-Ig is processed, but this is not the case with antigen.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Ricin A-chain containing immunotoxins directed against different epitopes on the CD2 molecule differ in their ability to kill normal and malignant T cells.

Immunoconjugates consisting of mAb covalently coupled to plant or bacterial toxins or to cytotoxic drugs have provided novel experimental reagents for the treatment of malignancies and autoimmune diseases. In this report, we analyzed the efficacy of three ricin A chain-containing immunotoxins (IT-A) which recognize different epitopes on the CD2 molecule (E rosette receptor) on human T cells. Although all IT-A had similar binding avidities and A-chain activities, one (RFT11-A) was 100-1000-fold more effective in killing normal and malignant T cells than the others (35.1-A, 9.6-A). Immunoprecipitation experiments confirmed that all IT-A bound to the CD2 molecule. However, cross-blocking experiments, differential proteolysis with trypsin, and T cell co-activation experiments showed that the less effective IT-A, 35.1-A and 9.6-A, bound to an epitope far from the cell membrane (region I), whereas the more effective IT-A, RFT11-A bound to an epitope closer to the membrane (region II). Using cellular RIA and immunoelectron microscopy, it was shown that both RFT11-A and 35.1-A were rapidly internalized by T cells, but that their intracellular fates differed. The more toxic IT-A, RFT11-A, was retained for longer periods of time inside the cells and was more slowly degraded than the less effective IT-A, 35.1-A, which was rapidly transported to lysosomes, digested, and expelled. These results demonstrate that different IT-A targeting the same surface molecule can differ markedly in potency, and that the epitope recognized by an IT-A may have a significant impact on the ability of the IT-A to insert into cell membranes, translocate to the cytosol, and kill cells.

Antibodies, Monoclonal↗
PubMed1988

HIV-infected cells are killed by rCD4-ricin A chain.

The gp120 envelope glycoprotein of the human immunodeficiency virus (HIV), which is expressed on the surface of many HIV-infected cells, binds to the cell surface molecule CD4. Soluble derivatives of recombinant CD4 (rCD4) that bind gp120 with high affinity are attractive vehicles for targeting a cytotoxic reagent to HIV-infected cells. Soluble rCD4 was conjugated to the active subunit of the toxin ricin. This conjugate killed HIV-infected H9 cells but was 1/1000 as toxic to uninfected H9 cells (which do not express gp120) and was not toxic to Daudi cells (which express major histocompatibility class II antigens, the putative natural ligand for cell surface CD4). Specific killing of infected cells can be blocked by rgp120, rCD4, or a monoclonal antibody to the gp120 binding site on CD4.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1988

Large scale preparation of immunotoxins constructed with the Fab' fragment of IgG1 murine monoclonal antibodies and chemically deglycosylated ricin A chain.

In this report, we describe a method for the preparation of large amounts (grams) of immunotoxins (ITs) consisting of Fab' fragments of murine IgG1 monoclonal antibodies conjugated to chemically deglycosylated ricin A chain (dgA). The preparation of Fab' and dgA chain and the purification of the Fab'-dgA IT were accomplished by gel filtrations and affinity chromatography utilizing six Pharmacia Bioprocess columns (Sephadex G-25M, Sephacryl S-200HR and Blue Sepharose CL-4B) integrated into a semi-automatic chromatography system controlled by a Pharmacia C3-process controller. The final Fab'-dgA ITs were highly purified, potent, sterile and low in endotoxin concentration.

Antibodies, Monoclonal↗
PubMed1988

Ricin B chain-containing immunotoxins prepared with heat-denatured B chain lacking galactose-binding ability potentiate the cytotoxicity of a cell-reactive ricin A chain immunotoxin.

Ricin B chain incubated at 37 degrees C in the absence of lactose loses its ability to bind the galactose-containing protein, asialofetuin. Circular dichroism analysis of the B chain during thermal denaturation indicates that the loss of galactose-binding ability by the B chain correlates with limited unfolding of the molecule. As a result of this conformational change, disulfide bonds that are shielded from the solvent by the compact folded structure of the B chain become exposed and the chitobiosyl cores of both N-linked oligomannose chains become susceptible to cleavage by endoglycosidases. The heat-denatured B chain does not enhance the toxicity of a ricin A chain-containing rabbit anti-human immunoglobulin (RAHIg-A) to Daudi cells. However, when heat-denatured B chain is coupled to goat anti-rabbit immunoglobulin (GARIg), the resulting immunotoxin, GARIg-hdB, potentiates the killing of RAHIg-A-treated Daudi cells to an extent similar to that of an immunotoxin prepared with GARIg and native B chain. These results indicate that the native, galactose-binding structure of the B chain is not necessary to enhance the cytotoxicity of the cell-reactive A chain immunotoxin (IT-A) and suggests that regions of the B chain exposed by unfolding the molecule may mediate potentiation of cytotoxicity.

Adjuvants, Immunologic↗
PubMed1988

Lymphokine-mediated regulation of the proliferative response of clones of T helper 1 and T helper 2 cells.

Murine Th1 and Th2 subsets differ not only in the lymphokines they produce, but also functionally. It is not clear what factors influence the preferential activation of one subset versus the other and what regulatory interactions exist between them. The purpose of this study was to examine the effect of lymphokines produced by clones of Th1 cells (IL-2 and IFN-gamma), Th2 cells (IL-4), and APC (IL-1) on the proliferative response of Th1 and Th2 cells after antigenic stimulation. Activation of both types of clones in the presence of antigen and APC resulted in the acquisition of responsiveness to the proliferative effects of both IL-2 and IL-4, although Th2 cells were more responsive to IL-4 than Th1 cells. Responsiveness of Th1 and Th2 cells to both lymphokines decreased with time after initial antigenic activation; Th1 cells lost their responsiveness to IL-4 more rapidly and to IL-2 more slowly than Th2 cells. IFN-gamma partially inhibited the IL-2 and IL-4-mediated proliferation of Th2, but not Th1 cells. Although the presence of IL-1 was not required for the response of Th1 or Th2 cells to IL-4, its presence resulted in a synergistic effect with IL-2 or IL-4 in Th2 but not in Th1 cells. Both subsets responded to a mixture of IL-2 and IL-4 in synergistic fashion. Delayed addition and wash-out experiments indicated that both IL-2 and IL-4 had to be present simultaneously in order for synergy to occur. These results suggest that Th cell subsets might regulate each other via the lymphokines that they secrete and that the pathways of IL-2 and IL-4 mediated proliferation are interrelated.

Animals↗