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A Zlotnik

Publications and source records attributed to A Zlotnik.

At least 127 records · Page 7Linked to original sources
PubMed1988

Identification of IL-6 as a T cell-derived factor that enhances the proliferative response of thymocytes to IL-4 and phorbol myristate acetate.

Thymocytes undergo a vigorous proliferative response when stimulated with a combination of IL-4 and PMA. We have found that conA-induced supernatants from a number of Th cell clones could enhance the level of IL-4/PMA-induced proliferation of unseparated thymocytes 0.5- to 2-fold and of peanut agglutinin-positive thymocytes 2- to 10-fold. These supernatants did not contain IL-2 or IFN-gamma, and the enhancing activity could be chromatographically separated from IL-3, -4, -5, and granulocyte/macrophage CSF. The possibility that the thymocyte enhancement factor contained in these supernatants was IL-6 was suggested when murine rIL-6 was found to have similar activity. Further evidence for the identity of these two factors was obtained when an IL-6 assay, based on plasmacytoma growth, was used to test column fractions showing thymocyte enhancement. All fractions active in the thymocyte enhancement assay also had activity in the plasmacytoma growth assay. These observations suggest that the thymocyte-stimulating activity present in the T cell supernatants was due to IL-6.

Adjuvants, Immunologic↗
PubMed1988

B cell stimulatory factor 1 induces lobster agglutinin 1-separated mouse thymocytes to express cytotoxic T lymphocyte activity.

Mouse thymocytes low in surface sialic acid were prepared by using the lectin lobster agglutinin 1 (LAg1). These LAg1-thymocytes do not become CTL when incubated with Con A or Con A plus mouse rIL-2, whereas unseparated thymocytes and thymocytes with high levels of surface sialic acid develop good levels of polyclonal CTL activity under these conditions. However, LAg1- thymocytes developed high levels of CTL activity when incubated with B cell stimulatory factor-1 (BSF-1), provided as the supernatant of the rBSF-1-secreting T cell hybridoma D9-C1.12.17. Affinity-purified BSF-1 from D9-C1 supernatant and rBSF-1 also stimulated these cells to become CTL, but they were not as active as the D9-C1 supernatant. The ability of D9-C1 supernatant and of affinity-purified BSF-1 to induce CTL activity was inhibited by the anti-BSF-1 mAb 11B11. Moreover, this mAb inhibited the ability of 24-h Con A-stimulated spleen cell supernatant to induce these cells to express CTL activity. 11B11 also inhibited LAg1+ thymocytes from becoming CTL when stimulated with Con A alone. These experiments suggest that BSF-1 is required for LAg1- and LAg1+ thymocytes to become CTL.

Animals↗
PubMed1988

Tumor necrosis factor alpha/cachectin is a growth factor for thymocytes. Synergistic interactions with other cytokines.

Recombinant murine (rm) TNF-alpha but not recombinant human (rh) TNF-alpha induces the proliferation of murine thymocytes in the presence of a comitogenic stimulus. This effect does not appear to be due to the production of significant levels of IL-1, IL-2, or IL-4. although not directly mitogenic (i.e., in the absence of PHA-P) for thymocytes, rmTNF-alpha amplifies the direct mitogenic signals from hIL-1 and rhIL-2 but not rmIL-4. In the presence of PHA-P, thymocytes stimulated with hIL-1, rhIL-2, and rmIL-4 produced significant amounts of TNF-alpha. Although rhTNF-alpha does not induce a proliferative response, it will competitively inhibit the proliferative response of thymocytes to rmTNF-alpha. These data suggest a critical role for TNF-alpha in the intrathymic proliferation of developing T cells.

Animals↗
PubMed1988

Induction of class I and class II MHC antigen expression on murine bone marrow-derived macrophages by IL-4 (B cell stimulatory factor 1).

We have studied the effects of IL-4 (B cell stimulatory factor 1) on the expression of MHC gene products in normal bone marrow-derived macrophages, peritoneal macrophages, and the myelomonocytic cell line WEHI-3. Using both IL-4-containing T cell supernatant and rIL-4, we have observed significant induction of both class I and class II MHC surface expression (about 1.5- to 4-fold increase) in 2-, 3-, and 4-day cultures of bone marrow-derived macrophages. This induction was also apparent at the mRNA level as assessed by Northern blot analysis using A beta, E alpha, and class I probes. Kinetic analysis revealed that induction of class II mRNA by IL-4 was slower than induction by IFN-gamma, requiring 48 h before a significant increase was noted. The magnitude of MHC induction by IL-4 was not as great as that seen with IFN-gamma, which was found to increase surface expression of MHC antigens two- to eightfold. IL-4 also differs from IFN-gamma in the repertoire of macrophages responsive to it. IL-4 was unable to induce class I or class II expression in either thioglycolate-elicited peritoneal macrophages or WEHI-3 cells whereas IFN-gamma induced MHC antigen expression on both cell types under the same conditions. These data demonstrate that IL-4 is capable of inducing both class I and class II MHC gene products in some, but not all, macrophages.

Animals↗
PubMed1988

The AKR thymoma BW5147 is able to produce lymphokines when stimulated with calcium ionophore and phorbol ester.

We produced the T cell hybridoma D9C1.12.17 by fusing an IL-4-producing T cell clone D9.1Hi with the AKR thymoma BW5147. The resulting hybridoma produced IL-2 as well as IL-4 even though none of the parental cells produced IL-2 after stimulation with Con A. The production of IL-2 was confirmed at the mRNA level by using an S1 nuclease protection assay. Further analysis indicated that Con A-induced IL-2 production was a common phenomenon among T cell hybridomas derived from this fusion. Although BW5147 does not produce detectable lymphokines after Con A stimulation, this line was able to produce IL-2, granulocyte-macrophage colony stimulating factor, and small amounts of IL-3 and IFN-gamma when stimulated with calcium ionophore and phorbol ester. The latter agents are thought to mimic the activating signal(s) delivered through the Ag:MHC TCR. This observation indicates that BW5147 has the ability to produce lymphokines but may lack component(s) which couple the extracellular signal to lymphokine production, and suggests that in T cell hybridomas, part of the spectrum of lymphokines produced may be contributed by BW5147.

Animals↗
PubMed1988

Up-regulation of interleukin 4 receptor expression on immature (Lyt-2-/L3T4-) thymocytes.

In this report, the effect of interleukin 4 (IL-4) on the growth and differentiation of Lyt-2-/L3T4-(2-4-) thymocytes was investigated. It was found that these thymocytes proliferated extensively when cultured in the presence of IL-4 + phorbol myristate acetate without apparent differentiation to Lyt-2+ or L3T4+ cells. We also demonstrated that 2-4- thymocytes constitutively express a high affinity (dissociation constant of 20 to 40 pM) receptor for IL-4. Freshly isolated 2-4- thymocytes expressed on average about 100 IL-4 receptors per cell, but the number of receptors increased approximately 8-fold within 3 days after activation by IL-4 + phorbol myristate acetate. These findings suggest that IL-4 may play an important role in T cell ontogeny by promoting self-renewal of stem cells within the thymus.

Animals↗
PubMed1987

Interferon-gamma is produced by activated immature mouse thymocytes and inhibits the interleukin 4-induced proliferation of immature thymocytes.

We have recently shown that interleukin 4 (IL-4) (formerly called BSF-1) is a potent stimulator of fetal and adult immature thymocyte proliferation and that adult L3T4-/Lyt-2-thymocytes can be stimulated by calcium ionophore (A23187) and phorbol ester to secrete IL-4 (Zlotnik, A., J. Ransom, G. Frank, M. Fischer, and M. Howard. 1987. Proc. Natl. Acad. Sci. (USA) 84:3856). This report shows that fetal thymocytes (day 15 of gestation) can also be activated to produce IL-4 suggesting that IL-4 may be a mediator of fetal as well as adult immature thymocyte proliferation. Furthermore, we demonstrate that interferon-gamma (IFN-gamma) inhibits the IL-4-mediated proliferation of both fetal and adult L3T4-/Lyt-2-thymocytes. The inhibition of proliferation is blocked by anti-IFN-gamma antibody and is unaffected by indomethacin suggesting that IFN-gamma directly inhibits immature thymocyte proliferation. IFN-gamma does not block the IL-4/phorbol myristate acetate-mediated proliferation of an adult thymocyte population, which is enriched for L3T4-/Lyt-2+ and L3T4+/Lyt-2- cells, suggesting that the inhibitory effect of IFN-gamma is limited to the immature thymocyte population. Both fetal (day 15) and adult L3T4-/Lyt-2--thymocytes can be activated to secrete an IFN-gamma like activity. This activity is neutralized by a monoclonal anti-IFN-gamma antibody indicating that the activity is due to IFN-gamma. mRNA analysis of adult L3T4-/Lyt-2- thymocytes stimulated with A23187 and phorbol myristate acetate confirms that mRNA for both IL-4 and IFN-gamma is induced in adult L3T4-/Lyt-2- thymocytes. These results indicate that IL-4 and IFN-gamma can regulate immature thymocyte proliferation.

Animals↗
PubMed1987

Lymphokine-mediated induction of antigen-presenting ability in thymic stromal cells.

We have established and characterized long term thymic stromal cultures from BALB/c (H-2d) and CBA/J (H-2k) mice. All cultures contained multiple adherent cell types, whereas some also contained thymic macrophages (TM). Culture supernatants from all cultures tested contained macrophage colony-stimulating factor activity, whereas only cultures with TM had soluble or membrane-associated interleukin (IL)-1. However, a thymic epithelial cell line (3D . 1), cloned from one of these cultures, produced IL-1 bioactivity. Further analysis confirmed the production of IL-1 alpha mRNA by the epithelial cell. No IL-2 or IL-4 (formerly called B cell stimulatory factor 1) activity was detected in any of the cultures. Antigen-presenting (AP) ability was determined using the chicken ovalbumin (OVA)-specific, I-Ad-restricted T cell hybridoma 3DO-18.3. Harvested TM exhibited antigen-specific, Ia-restricted AP ability which was enhanced by IL-4 as well as interferon-gamma (IFN-gamma). In contrast, AP ability was detected in non-macrophage stromal cell cultures (NMSC) only after preincubation with IFN-gamma. AP by preinduced NMSC was also Ia-restricted and could be blocked by anti-I-Ad antibodies. Since the T cell receptor of 3DO-18.3 is known to recognize a peptide produced by CNBr degradation of OVA, these observations suggest that both TM and NMSC can process OVA to produce this peptide. Glutaraldehyde-fixation experiments confirmed that NMSC must process native OVA into antigenic peptides for successful AP. Assays using several cloned stromal cell lines of different lineages suggested that only epithelial cells could be induced with IFN-gamma to exhibit competent AP. Given the possible role for IFN-gamma in the maintenance of Ia in the thymus, we investigated whether IFN-gamma production could be ascribed to a subpopulation of thymocytes. Culture supernatants from calcium ionophore and phorbol ester-stimulated peanut agglutinin-negative, but not peanut agglutinin-positive, thymocytes induced AP ability in NMSC. Thus, some thymocytes can produce an Ia-inducing lymphokine (most likely IFN-gamma) which may play an important role in T cell ontogeny through its effects on both thymic macrophages and thymic epithelial cells.

Animals↗
PubMed1987

Evidence for effects of interleukin 4 (B cell stimulatory factor 1) on macrophages: enhancement of antigen presenting ability of bone marrow-derived macrophages.

We have studied the effects of recombinant mouse interleukin 4 (IL 4) (previously known as B cell stimulatory factor 1) on the antigen-presenting ability of murine splenic B cells and bone marrow macrophages. Our assay is based on the induction of antigen-presenting ability in these cells after incubation with IL 4 for 24 hr. The presenting cells were then used to stimulate IL 2 production by antigen-specific, I-Ad-restricted T cell hybridomas, a response mainly dependent on the induction of Ia antigens. Consistent with our previously published data using partially purified natural IL 4, we show here that recombinant IL 4 (but not interferon-gamma (IFN-gamma) or IL 1) induces antigen-presenting ability in B cells. Recombinant IL 4 was also found to induce antigen-presenting ability in a cloned, bone marrow derived-macrophage cell line (14M1.4), and in normal bone marrow-derived macrophages. These macrophage populations also respond to IFN-gamma showing enhanced antigen-presenting ability (mediated by increased Ia antigen expression). A small but significant increase in Ia antigen expression was also detected in 14M1.4 macrophages induced with IL 4. However, additional analysis suggested that the effect of IL 4 on 14M1.4 is different from that of IFN-gamma, because IL 4 (but not IFN-gamma) is able to maintain the viability and increase the size of and metabolic activity of bone marrow macrophages. However, IL 4 may not affect all macrophages because the macrophage cell line P388D1, which responds to IFN-gamma, failed to show enhanced antigen-presenting function after stimulation with IL 4. These observations indicate that IL 4, a lymphokine previously considered to be B cell lineage specific, has effects on macrophages and may be involved in their activation.

Animals↗
PubMed1987

Interleukin 1 modulates messenger RNA levels of lymphokines and of other molecules associated with T cell activation in the T cell lymphoma LBRM33-1A5.

We have investigated the mechanism of action of IL 1 on T cell activation. For this purpose, we analyzed the content of specific messenger RNA for lymphokines and other genes that are associated with T cell activation in the murine IL 1-dependent T cell lymphoma LBRM33-1A5. Using cloned genes for IL 2, IL 3, TGF-beta, TY5, IL 2 receptor, Ly-1, c-myc, and p53 as probes in the S1 nuclease protection assay, we compared the amount of specific transcripts among total RNA prepared from unstimulated cells, IL 1 alpha or PHA-stimulated cells, and PHA plus IL 1 alpha-stimulated cells. IL 1 alpha augmented the PHA-induced accumulation of IL 2 mRNA with a magnitude comparable to the amount of IL 2 produced, suggesting that IL 1 alpha modulates IL 2 gene expression at the RNA level. Similar results were obtained with IL 3. We also observed that Ly-1 mRNA appears after PHA treatment and its accumulation was augmented by IL 1 alpha addition. On the basis of the effects of IL 1 alpha and/or PHA treatments on gene expression, we classified these genes into four groups. In all cases, IL 1 alpha seemed to affect mRNA levels quantitatively. These observations support previously described characteristics of this cytokine as a co-stimulator of T cell activation.

Cell Line↗
PubMed1987

Interleukin 4 is a growth factor for activated thymocytes: possible role in T-cell ontogeny.

We have shown that recombinant or natural interleukin 4 (IL-4) (formerly called B-cell stimulatory factor 1) induces proliferation of activated adult or fetal thymocytes. In the case of adult thymocytes, IL-4 in combination with Con A or phorbol 12-myristate 13-acetate (PMA) stimulated the proliferation of peanut agglutinin (PNA)-negative (-) thymocytes, while PNA-positive (+) thymocytes showed only marginal responses. Further investigation revealed that day 14-17 fetal thymocytes, purified L3T4- LyT2- double-negative adult thymocytes, and single positive L3T4+ LyT2- or L3T4- LyT2+ thymocytes failed to respond to IL-4 or PMA alone but proliferated strongly with both IL-4 and PMA. In contrast, purified double-positive L3T4+ LyT2+ adult thymocytes showed only a marginal proliferative response to these stimuli. Responsiveness of thymic subpopulations to PMA and IL-4 could be inhibited with anti-IL-4 but not with anti-IL-2 monoclonal antibodies, indicating that they were IL-2 independent. Finally, we have observed that supernatants from calcium ionophore and PMA-stimulated adult double-negative L3T4- LyT2- thymocytes induce proliferation of double-negative adult thymocytes. This latter response is inhibited by anti-IL-4 monoclonal antibodies, suggesting that under appropriate stimulation conditions, these immature thymocytes are able to produce IL-4. These observations suggest a role for IL-4 in T-cell ontogeny.

Animals↗
PubMed1986

B cell stimulatory factor-1 enhances the IgE response of lipopolysaccharide-activated B cells.

Supernatants from some mouse helper T cell (TH) lines contain an activity that can enhance IgE production by lipopolysaccharide (LPS)-stimulated B cells by at least two orders of magnitude. During purification, this activity could not be resolved from B cell stimulatory factor-1 (BSF-1). Highly purified BSF-1 from a different source, the T lymphoma cell line EL-4, enhanced IgE production to the same extent as TH supernatants, which suggests that BSF-1 is responsible for this increase in IgE production. Monoclonal antibody to BSF-1 totally inhibits the IgE-enhancing activity of a TH supernatant, lending further support to this conclusion. The effects of BSF-1 on LPS-stimulated B cells are specific for IgE and, as previously reported, IgG1 and IgG3, because the levels of IgM, IgG2a, IgG2b, and IgA in the cultures change relatively little when BSF-1 is added.

Animals↗
PubMed1986

Chronic infection due to Mycobacterium intracellulare in mice: association with macrophage release of prostaglandin E2 and reversal by injection of indomethacin, muramyl dipeptide, or interferon-gamma.

As a model for the study of human atypical mycobacterial disease, we explored the basis for the prolonged mycobacteriosis in mice infected with Mycobacterium intracellulare. Two weeks after i.v. injection of mycobacteria, peritoneal macrophages were found to be activated, as indicated by their capacity to produce large amounts of superoxide anion (O2-) in response to phorbol myristate acetate (PMA) or viable M. intracellulare. However, 4 wk after infection, despite the continued presence of large numbers of mycobacteria in the spleen, macrophages from infected animals produced low amounts of O2-. Unfractionated spleen cells from mice infected 4 wk earlier produced increased amounts of interleukin 2 and interferon (IFN) when stimulated with the mitogen concanavalin A, but less of these lymphokines than unstimulated cells when exposed to antigens derived from M. intracellulare, suggesting production of an inhibitory factor. Spleen cells from infected mice were not stimulated to incorporate [3H]thymidine by exposure to mycobacterial antigens; but this unresponsiveness could be reversed by addition of indomethacin to the cultures. Additional investigation showed that macrophages from infected animals produced large amounts of prostaglandin E2 (PGE2) when stimulated by mycobacterial antigens. In vitro, such concentrations of PGE2 inhibited uptake of [3H]thymidine by stimulated spleen lymphocytes from infected animals. Thus, it seemed likely that in infected animals, macrophage-derived PG suppressed production of IFN-gamma by lymphocytes, which in turn prevented activation of the macrophages to full microbicidal activity. To test this hypothesis, we administered either indomethacin, IFN-gamma, or muramyl dipeptide to infected mice. Mice treated with each of these agents showed decreased spleen and lung weights, and decreased numbers of viable mycobacteria in these organs. These results support the concept that interaction between the host and M. intracellulare is modulated profoundly by PG and suggest that administration of agents that directly promote macrophage activation can enhance resistance to infection by this organism.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1986

Activation of IL 1-dependent and IL 1-independent T cell lines by calcium ionophore and phorbol ester.

We have studied the activation of interleukin 1 (IL 1)-dependent and IL 1-independent T cell lines, specifically their capacity to produce and secrete interleukin 2 (IL 2). The IL 1-dependent T cell lymphoma LBRM33-1A5.47, which requires phytohemagglutinin (PHA) and IL 1 to produce IL 2, was compared with the IL 1-independent T cell lymphoma LBRM33-5A4 and T cell hybridomas DO-11.10/S4.4 and 3DO-54.8. The latter hybridomas do not require exogenous IL 1 to produce IL 2 in response to mitogens or ovalbumin (OVA)/I-Ad. Even though IL 1 is not required by these IL 1-independent T cell lines, we tested whether IL 1 could modulate their response but found no significant effect of exogenous IL 1. We then studied the activation of these T cell lines by the calcium ionophore A23187 and phorbol myristate acetate (PMA). In the case of the IL 1-dependent line LBRM33-1A5.47, there was a strong response when both A23187 and PMA were used simultaneously. We subsequently found that A23187 can replace PHA, and PMA can replace IL 1 in the activation of this cell line to IL 2 production. These observations suggest that the signal(s) provided by PHA and IL 1 involve at least in part a calcium flux, and activation of protein kinase C. Parallel experiments with the use of the IL 1-independent T cell lines showed a strong response to both agents when used simultaneously. A modest response observed to A23187 alone was always enhanced by the addition of PMA. No response was observed to PMA alone. IL 1-rich P388D1 supernatant could replace the enhancing effect of PMA in the response of the IL 1-independent T cell lines. We suggest that the activating signals provided by A23187 and PMA are at least part of the sequence of events that lead to production of IL 2 in either IL 1-dependent or IL 1-independent T cell lines. In IL 1-independent T cell lines, however, both of the activating signals studied may be delivered through stimulation of the Antigen-MHC T cell receptor.

Animals↗
PubMed1985

Effect of prostaglandin E2 on the gamma-interferon induction of antigen-presenting ability in P388D1 cells and on IL-2 production by T-cell hybridomas.

The effect of prostaglandin E2 on the gamma-interferon (IFN-gamma)-mediated induction of Ia expression and antigen-presenting activity in macrophage cell lines was studied. Using a lymphokine preparation obtained from the T-cell hybridoma FS7-20.6.18 (known to produce interferon) to induce the expression of Ia in P388D1 cells, the influence of PGE2 on this phenomenon was studied. Screening of the cell cultures by indirect immunofluorescence using an anti-I-Ad monoclonal antibody confirmed the inhibitory effect of PGE2 in the induction of I-Ad. However, the inhibition of the antigen-presenting ability of these cells, as measured by their capacity to stimulate interleukin 2 (IL-2) production by antigen-specific, I-region-restricted (Ag/I) T-cell hybridomas, was more difficult to demonstrate and was only evident when using low concentrations of Ia-inducing lymphokines or when using "low avidity" T-cell hybridomas. The latter were distinguished by the limited response (in the form of IL-2 production) that was observed when they were tested with P388D1 cells that had been induced with IFN-gamma. By contrast, PGE2 had profound inhibitory effects on the ability of T-cell hybridomas to secrete IL-2 in response to Ag/I or concanavalin A. These results suggest that although PGE2 inhibits the full induction of Ia on macrophages, it has little effect on the induction of Ag/I presentation by the same cells, probably because most T cells require relatively low levels of Ia on the surface of presenting cells. T-cell responses to Ag/I are inhibited, however, because of the effects of PGE2 on the T cells themselves.

Animals↗
PubMed1985

Activation of an interleukin-1-responsive T-cell lymphoma by fixed P388D1 macrophages and an antibody against the Ag:MHC T-cell receptor.

We have characterized the activation of the interleukin 1 (IL-1)-responsive T-cell lymphoma LBRM33-1A5-47 to interleukin 2 (IL-2) production by phytohemagglutinin (PHA) and IL-1. The signal provided by soluble IL-1 could be replaced by fixed P388D1 cells and the signal provided by PHA by a monoclonal antibody directed against an allotypic determinant of the Ag/MHC T-cell receptor (KJ16-133). The signal provided by fixed P388D1 does not appear to be due to alloreactivity. Instead, it appears to be due to a membrane-bound IL-1. The implications of these observations are discussed.

Animals↗