Antitumor and immunotherapeutic effects of activated invasive T lymphoma cells that display short-term interleukin 1alpha expression.
(65/39207)
Expression of cytokines in malignant cells represents a novel approach for therapeutic treatment of tumors. Previously, we demonstrated the immunostimulatory effectiveness of interleukin 1alpha (IL-1alpha) gene transfer in experimental fibrosarcoma tumors. Here, we report the antitumor and immunotherapeutic effects of short-term expression of IL-1alpha by malignant T lymphoma cells. Activation in culture of T lymphoma cells with lipopolysaccharide-stimulated macrophages induces the expression of IL-1alpha. The short-term expression of IL-1alpha persists in the malignant T cells for a few days (approximately 3-6 days) after termination of the in vitro activation procedure and, thus, has the potential to stimulate antitumor immune responses in vivo. As an experimental tumor model, we used the RO1 invasive T lymphoma cell line. Upon i.v. inoculation, these cells invade the vertebral column and compress the spinal cord, resulting in hind leg paralysis and death of the mice. Activated RO1 cells, induced to express IL-1alpha in a short-term manner, manifested reduced tumorigenicity: approximately 75% of the mice injected with activated RO1 cells remained tumor free. IL-1 was shown to be essential for the eradication of activated T lymphoma cells because injection of activated RO1 cells together with IL-1-specific inhibitors, i.e., the IL-1 receptor antagonist or the M 20 IL-1 inhibitor, reversed reduced tumorigenicity patterns and led to progressive tumor growth and death of the mice. Furthermore, activated RO1 cells could serve as a treatment by intervening in the growth of violent RO1 cells after tumor take. Thus, when activated RO1 cells were injected 6 or 9 days after the inoculation of violent cells, mortality was significantly reduced. IL-1alpha, in its unique membrane-associated form, in addition to its cytosolic and secreted forms, may represent a focused adjuvant for potentiating antitumor immune responses at low levels of expression, below those that are toxic to the host. Further assessment of the immunotherapeutic potential of short-term expression of IL-1alpha in activated tumor cells may allow its improved application in the treatment of malignancies. (+info)
Cancer vaccines.
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It has been more than 100 years since the first reported attempts to activate a patient's immune system to eradicate developing cancers. Although a few of the subsequent vaccine studies demonstrated clinically significant treatment effects, active immunotherapy has not yet become an established cancer treatment modality. Two recent advances have allowed the design of more specific cancer vaccine approaches: improved molecular biology techniques and a greater understanding of the mechanisms involved in the activation of T cells. These advances have resulted in improved systemic antitumor immune responses in animal models. Because most tumor antigens recognized by T cells are still not known, the tumor cell itself is the best source of immunizing antigens. For this reason, most vaccine approaches currently being tested in the clinics use whole cancer cells that have been genetically modified to express genes that are now known to be critical mediators of immune system activation. In the future, the molecular definition of tumor-specific antigens that are recognized by activated T cells will allow the development of targeted antigen-specific vaccines for the treatment of patients with cancer. (+info)
Stat5 is required for IL-2-induced cell cycle progression of peripheral T cells.
(67/39207)
Many cytokines activate two highly homologous Stat proteins, 5a and 5b. Mice deficient in both genes lack all growth hormone and prolactin functions but retain functions associated with cytokines such as erythropoietin. Here, we demonstrate that, while lymphoid development is normal, Stat5a/b mutant peripheral T cells are profoundly deficient in proliferation and fail to undergo cell cycle progression or to express genes controlling cell cycle progression. In addition, the mice lack NK cells, develop splenomegaly, and have T cells with an activated phenotype, phenotypes seen in IL-2 receptor beta chain-deficient mice. These phenotypes are not seen in mice lacking Stat5a or Stat5b alone. The results demonstrate that the Stat5 proteins, redundantly, are essential mediators of IL-2 signaling in T cells. (+info)
Cellular and molecular characterization of the scurfy mouse mutant.
(68/39207)
Mice hemizygous (Xsf/Y) for the X-linked mutation scurfy (sf) develop a severe and rapidly fatal lymphoproliferative disease mediated by CD4+CD8- T lymphocytes. We have undertaken phenotypic and functional studies to more accurately identify the immunologic pathway(s) affected by this important mutation. Flow cytometric analyses of lymphoid cell populations reveal that scurfy syndrome is characterized by changes in several phenotypic parameters, including an increase in Mac-1+ cells and a decrease in B220+ cells, changes that may result from the production of extremely high levels of the cytokine granulocyte-macrophage CSF by scurfy T cells. Scurfy T cells also exhibit strong up-regulation of cell surface Ags indicative of in vivo activation, including CD69, CD25, CD80, and CD86. Both scurfy and normal T cells are responsive to two distinct signals provided by the TCR and by ligation of CD28; scurfy cells, however, are hyperresponsive to TCR ligation and exhibit a decreased requirement for costimulation through CD28 relative to normal controls. This hypersensitivity may result, in part, from increased costimulation through B7-1 and B7-2, whose expression is up-regulated on scurfy T cells. Although the specific defect leading to this hyperactivation has not been identified, we also demonstrate that scurfy T cells are less sensitive than normal controls to inhibitors of tyrosine kinases such as genistein and herbimycin A, and the immunosuppressant cyclosporin A. One interpretation of our data would suggest that the scurfy mutation results in a defect, which interferes with the normal down-regulation of T cell activation. (+info)
N-acetyl-L-cysteine inhibits primary human T cell responses at the dendritic cell level: association with NF-kappaB inhibition.
(69/39207)
N-acetyl-L-cysteine (NAC) is an antioxidant molecule endowed with immunomodulatory properties. To investigate the effect of NAC on the induction phase of T cell responses, we analyzed its action on human dendritic cells (DC) derived from adherent PBMC cultured with IL-4 and granulocyte-macrophage CSF. We first found that NAC inhibited the constitutive as well as the LPS-induced activity of the transcription factor NF-kappaB. In parallel, NAC was shown to down-regulate the production of cytokines by DC as well as their surface expression of HLA-DR, CD86 (B7-2), and CD40 molecules both at the basal state and upon LPS activation. NAC also inhibited DC responses induced by CD40 engagement. The inhibitory effects of NAC were not due to nonspecific toxicity as neither the viability of DC nor their mannose receptor-mediated endocytosis were modified by NAC. Finally, we found that the addition of NAC to MLR between naive T cells and allogeneic DC resulted in a profound inhibition of alloreactive responses, which could be attributed to a defect of DC as APC-independent T cell responses were not inhibited by NAC. Altogether, our results suggest that NAC might impair the generation of primary immune responses in humans through its inhibitory action on DC. (+info)
Characterization of TCR gene rearrangements during adult murine T cell development.
(70/39207)
Development of the alphabeta and gammadelta T cell lineages is dependent upon the rearrangement and expression of the TCRalpha and beta or gamma and delta genes, respectively. Although the timing and sequence of rearrangements of the TCRalpha and TCRbeta loci in adult murine thymic precursors has been characterized, no similar information is available for the TCRgamma and TCRdelta loci. In this report, we show that approximately half of the total TCRdelta alleles initiate rearrangements at the CD44highCD25+ stage, whereas the TCRbeta locus is mainly in germline configuration. In the subsequent CD44lowCD25+ stage, most TCRdelta alleles are fully recombined, whereas TCRbeta rearrangements are only complete on 10-30% of alleles. These results indicate that rearrangement at the TCRdelta locus can precede that of TCRbeta locus recombination by one developmental stage. In addition, we find a bias toward productive rearrangements of both TCRdelta and TCRgamma genes among CD44highCD25+ thymocytes, suggesting that functional gammadelta TCR complexes can be formed before the rearrangement of TCRbeta. These data support a model of lineage commitment in which sequential TCR gene rearrangements may influence alphabeta/gammadelta lineage decisions. Further, because TCR gene rearrangements are generally limited to T lineage cells, these analyses provide molecular evidence that irreversible commitment to the T lineage can occur as early as the CD44highCD25+ stage of development. (+info)
Surface expression and functional competence of CD3-independent TCR zeta-chains in immature thymocytes.
(71/39207)
In recombinase-deficient (RAG-2-/-) mice, double-negative thymocytes can be stimulated to proliferate and differentiate by anti-CD3 Abs. CD3 molecules are expressed on the surface of these cells in association with calnexin. In this study, we show that zeta-chains can be recovered as phosphorylated proteins in association with phosphorylated ZAP-70 from anti-CD3-stimulated RAG-2-/- thymocytes, even though they are not demonstrably associated with the CD3/calnexin complex. The lack of a physical association of zeta dimers with the CD3 complex in RAG-2-/- thymocytes and also in a pre-TCR-expressing cell line, as well as the efficient association of zeta dimers with ZAP-70 in the RAG-2-/- thymocytes, suggest that these zeta-chain dimers could contribute to pre-TCR signaling. This idea is supported by the finding that in RAG-2-/- zeta-deficient thymocytes, ZAP-70 and p120cbl were only weakly phosphorylated. (+info)
IL-15 induces the expression of chemokines and their receptors in T lymphocytes.
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IL-15 is a T cell growth factor that shares many biological activities with IL-2 and uses the same beta/gamma polypeptides of the IL-2R complex for signal transduction. Accumulating evidence implicates an important role for this cytokine in the inflammatory response of the host. Consistent with such a role, IL-15 has been shown to be a chemoattractant for T lymphocytes, NK cells, and neutrophils. Extending these observations, we now show that IL-15 is a potent inducer of CC-, CXC-, and C-type chemokines in T lymphocytes. In addition, we demonstrate that IL-15 induces CC chemokine receptors, but not CXC chemokine receptors, in a dose-dependent manner. Thus, our findings suggest that the proinflammatory effects of IL-15 at least in part may be due to the induction of chemokines and their receptors in T cells. Furthermore, we demonstrate that IL-15 promotes entry and replication of macrophage-tropic HIV in T lymphocytes and suggest a plausible mechanism by which IL-15, a cytokine that is elevated in HIV-infected individuals, may promote the transition of HIV displaying the M-tropic phenotype primarily associated with the initial transmission into the T cell-tropic phenotype that predominates as the disease progresses. (+info)