Modulation of T-cell activation by the glucocorticoid-induced leucine zipper factor via inhibition of nuclear factor kappaB.

Previously a novel gene was identified that encodes a glucocorticoid-induced leucine zipper (GILZ) whose expression is up-regulated by dexamethasone. This study analyzed the role of GILZ in the control of T-cell activation and its possible interaction with nuclear factor kappaB (NF-kappaB). Results indicate that GILZ inhibits both T-cell receptor (TCR)-induced interleukin-2/interleukin-2 receptor expression and NF-kappaB activity.

Cloning and expression of a short Fas ligand: A new alternatively spliced product of the mouse Fas ligand gene.

The Fas/FasL system mediates apoptosis in several different cell types, including T lymphocytes. Fas ligand (FasL), a 40-kD type II membrane protein also expressed in activated T cells, belongs to the tumor necrosis factor ligand family. We describe a new alternative splicing of mouse FasL, named FasL short (FasLs), cloned by reverse transcriptase-polymerase chain reaction.

Interleukin-6 (IL-6) prevents activation-induced cell death: IL-2-independent inhibition of Fas/fasL expression and cell death.

Triggering of the TCR/CD3 complex with specific antigen or anti-CD3 monoclonal antibody initiates activation-induced cell death (AICD) in mature T cells, an effect also mediated by the Fas/FasL system. We have previously shown that CD2 stimulation rescues T cells from TCR/CD3-induced apoptosis by decreasing the expression of Fas and FasL. In the present study, we examined whether the endogenous production of IL-2 plays a role in the effects mediated by CD2 triggering.

A new dexamethasone-induced gene of the leucine zipper family protects T lymphocytes from TCR/CD3-activated cell death.

By comparing mRNA species expressed in dexamethasone (DEX)-treated and untreated murine thymocytes, we have identified a gene, glucocorticoid-induced leucine zipper (GILZ), encoding a new member of the leucine zipper family. GILZ was found expressed in normal lymphocytes from thymus, spleen, and lymph nodes, whereas low or no expression was detected in other nonlymphoid tissues, including brain, kidney, and liver. In thymocytes and peripheral T cells, GILZ gene expression is induced by DEX.

T cell receptor iota an alternatively spliced product of the T cell receptor zeta gene.

It has been previously suggested that three alternative splicings of the murine T cell receptor (TCR) zeta gene are involved in the regulation of TCR/CD3 transduction signals. We here describe a new alternative splicing of this gene (TCR iota), cloned by reverse transcriptase-polymerase chain reaction, that is encoded by exons 1-7 and 10. The protein putatively encoded by TCR iota mRNA differs in its carboxy terminus from that coded by TCR0 as a consequence of the reading frame shift of exon 10.

Superantigen-induced peripheral T-cell deletion: the effects of chemical modification of antigen-presenting cells, interleukin-4 and glucocorticoid hormones.

Experiments were performed to evaluate the role of antigen-presenting cells (APC) and the effect of interleukin-4 (IL-4) and glucocorticoid hormone (GCH) exposure on the in vitro deletion of CD4+ CD8- and CD8+ CD4- T cells by staphylococcal enterotoxin B (SEB). APC fixation with the chemical cross-linker 1-ethyl-3-(3-dimethyl-aminopropyl) carbodiimide (ECDI) inhibited their capacity to induce SEB-specific deletion of mature T lymphocytes. Deletion was not influenced by treatment with anti-CD28 antibodies, which modulate T-cell activation.

Dexamethasone induces apoptosis in mouse natural killer cells and cytotoxic T lymphocytes.

Glucocorticoid hormones (GCH) induce apoptotic cell death in immature thymocytes through an active mechanism, characterized by extensive DNA fragmentation into oligonucleosomal subunits. This requires macromolecular synthesis and is inhibited by protein kinase C (PKC) inhibitors, interleukin-4 (IL-4) and heat shock (hs). We performed experiments to analyse the possible effect of GCH on more differentiated lymphocytes, i.

Long-term cultures of mouse bone marrow cells: a model for studying the generation of natural killer cells.

We investigated the generation of natural killer (NK) cells, using a long-term bone marrow culture (LTBMC) system. Mouse bone marrow cells were cultured for 2 weeks in complete medium without growth factors to obtain an enriched population of NK precursor cells. When these cells were recultured in the presence of interleukin-2 (IL-2) and conditioned medium (CM) from LTBMC, lytic NK cells were generated within 4 days.

Heat shock induces apoptosis in mouse thymocytes and protects them from glucocorticoid-induced cell death.

Thymocyte death is a complex phenomenon under the control of different signals and stimuli. We evaluated the effect of elevated temperature (heat shock, HS) on mouse thymocyte apoptosis. Incubation of thymocytes at 43 degrees C for 20 min induced DNA fragmentation and cell death, but it was also able to decrease the apoptosis induced by dexamethasone (DEX), TPA or Ca2+ ionophore.

Glucocorticoid-induced DNA fragmentation: role of protein-kinase-C activity.

Glucocorticoid hormones (GCH) and IL-2 induce apoptotic cell death by a PKC-dependent mechanism. IL-4 counteracts apoptosis by inhibiting PKC activity. GCH and IL-2 show antagonistic effects on apoptosis when administered together.

Effect of a new peptidyl-hypoxanthine derivative on natural killer cells and antitumor activity.

A new immunomodifier, [omega-(hypoxanthin-9-yl) pentoxy-carbonyl-leucyl-methionine] (RM06), was synthesized and its effect was evaluated on the activity of Natural Killer (NK) cells. Results indicate that RM06 is able to boost the NK activity of normal mice as well as to augment the regeneration of NK activity of lethally irradiated mice transplanted with syngeneic bone marrow (BM). This later effect also correlated with a significant increase in anti-tumor activity as evaluated by the resistance to metastasis in mice injected with syngeneic melanoma cells.

Growth of murine natural killer cells from bone marrow in vitro: role of TNF alpha and IFN gamma.

It has been previously shown that natural killer (NK) cell growth can be induced by interleukin-2 (IL-2) in bone marrow (BM) cultures and that other cytokines (CKs), including IL-1 alpha, act synergistically with IL-2. However, as the effect of IL-2 and IL-1 alpha could be due to direct stimulation of NK progenitor cell growth, as well as to the induction of other factors, we analysed the role of the endogenous production of CKs in BM cultures. Results show that mRNAs specific for tumour necrosis factor-alpha (TNF alpha) and interferon-gamma (IFN gamma) are detectable within hours in BM cultures supplemented with IL-2 and IL-1 alpha, and that the amount is higher when both IL-2 and IL-1 alpha are present.

In vivo effects of cytokines on development of natural killer cells and antitumor activity in lethally irradiated bone marrow transplanted recipients.

We have evaluated the effects of combinations of various cytokines on the reconstitution of natural killer (NK) cell activity and resistance to metastases from B16 melanoma, in lethally irradiated mice transplanted with syngeneic bone marrow. Treatment with some combinations of interleukin-2 (IL-2) and other cytokines (IL-2 + IL-1 + TNF alpha or IL-2 + IL-1 + LT) induced appreciably greater and more rapid augmentation of NK cell regeneration than IL-2 alone, as measured in vitro in the 4-h 51Cr release assay against YAC-1 or in vivo in an assay of lung clearance of 125IUdR-labeled tumor cells. The same treatments also induced significant augmentation of in vivo resistance against pulmonary metastases in C57BL/6 mice injected with B16 melanoma cells.