The essential role of endogenous IFN alpha/beta in the anti-metastatic action of sensitized T lymphocytes in mice injected with Friend erythroleukemia cells

Spatiotemporal trafficking of HIV in human plasmacytoid dendritic cells defines a persistently IFN-α-producing and partially matured phenotype

Plasmacytoid DCs (pDCs) are innate immune cells that are specialized to produce IFN-α and to activate adaptive immune responses. Although IFN-α inhibits HIV-1 replication in vitro, the production of IFN-α by HIV-activated pDCs in vivo may contribute more to HIV pathogenesis than to protection. We have now shown that HIV-stimulated human pDCs allow for persistent IFN-α production upon repeated stimulation, express low levels of maturation molecules, and stimulate weak T cell responses. Persistent IFN-α production by HIV-stimulated pDCs correlated with increased levels of IRF7 and was dependent upon the autocrine IFN-α/β receptor feedback loop. Because it has been shown that early endosomal trafficking of TLR9 agonists causes strong activation of the IFN-α pathway but weak activation of the NF-κB pathway, we sought to investigate whether early endosomal trafficking of HIV, a TLR7 agonist, leads to the IFN-α-producing phenotype we observed. We demonstrated that HIV preferentially traffics to the early endosome in human pDCs and therefore skews pDCs toward a partially matured, persistently IFN-α-secreting phenotype.

Antileukemia and antitumor effects of the graft-versus-host disease: a new immunovirological approach

In leukemic mice, the native host's explicit and well-defined immune reactions to the leukemia virus (a strong exogenous antigen) and to leukemia cells (pretending in their native hosts to be protected "self" elements) are extinguished and replaced in GvHD (graft-versus-host disease) by those of the immunocompetent donor cells. In many cases, the GvHD-inducer donors display genetically encoded resistance to the leukemia virus. In human patients only antileukemia and anti-tumor cell immune reactions are mobilized; thus, patients are deprived of immune reactions to a strong exogenous antigen (the elusive human leukemia-sarcoma retroviruses). The innate and adaptive immune systems of mice have to sustain the immunosuppressive effects of leukemia-inducing retroviruses. Human patients due to the lack of leukemiainducing retroviral pathogens (if they exist, they have not as yet been discovered), escape such immunological downgrading. After studying leukemogenic retroviruses in murine and feline (and other mammalian) hosts, it is very difficult to dismiss retroviral etiology for human leukemias and sarcomas. Since no characterized and thus recognized leukemogenic-sarcomagenic retroviral agents are being isolated from the vast majority of human leukemias-sarcomas, the treatment for these conditions in mice and in human patients vastly differ. It is immunological and biological modalities (alpha interferons; vaccines; adoptive lymphocyte therapy) that dominate the treatment of murine leukemias, whereas combination chemotherapy remains the main remission-inducing agent in human leukemias-lymphomas and sarcomas (as humanized monoclonal antibodies and immunotoxins move in). Yet, in this apparently different backgrounds in Mus and Homo, GvHD, as a treatment modality, appears to work well in both hosts, by replacing the hosts' anti-leukemia and anti-tumor immune faculties with those of the donor. The clinical application of GvHD in the treatment of human leukemias-lymphomas and malignant solid tumors remains a force worthy of pursuit, refinement and strengthening. Graft engineering and modifications of the inner immunological environment of the recipient host by the activation or administration of tumor memory T cells, selected Treg cells and natural killer (NKT) cell classes and cytokines, and the improved pharmacotherapy of GvHD without reducing its antitumor efficacy, will raise the value of GvHD to the higher ranks of the effective antitumor immunotherapeutical measures. Clinical interventions of HCT/HSCT (hematopoietic cell/stem cell transplants) are now applicable to an extended spectrum of malignant diseases in human patients, being available to elderly patients, who receive non-myeloablative conditioning, are re-enforced by post-transplant donor lymphocyte (NK cell and immune T cell) infusions and post-transplant vaccinations, and the donor cells may derive from engineered grafts, or from cord blood with reduced GvHD, but increased GvL/GvT-inducing capabilities (graft-versus leukemia/tumor). Post-transplant T cell transfusions are possible only if selected leukemia antigen-specific T cell clones are available. In verbatim quotation: "Ultimately, advances in separation of GvT from GvHD will further enhance the potential of allogeneic HCT as a curative treatment for hematological malignancies" (Rezvani, A.R. and Storb, R.F., Journal of Autoimmunity 30:172-179, 2008 (see in the text)). It may be added: for cure, a combination of the GvL/T effects with new targeted therapeutic modalities, as elaborated on in this article, will be necessary.

The antitumor effects of interferon: A personal history

Early experiments showed that administration of mouse interferon preparations inhibited the development of viral-induced or spontaneous viral associated leukemias in mice. Interferon alpha/beta was also shown to inhibit the growth of transplantable tumors of different origins in all strains of mice tested. The finding that interferon alpha/beta inhibited the growth of sublines of tumors selected for resistance to interferon alpha/beta indicated the role of interferon induced host mechanisms in the antitumor effects observed. The different host antitumor mechanisms and especially the interaction of interferon alpha/beta with the immune system have been briefly discussed. Injection of mice with a neutralizing antibody to interferon alpha/beta demonstrated the essential role of endogenous interferon alpha/beta in the defense of the mouse against the development of syngeneic, allogeneic and xenogeneic tumors.

Interferon signalling network in innate defence

Interferons (IFNs) elicit multifaceted effects in host innate defence. Accumulating evidence revealed that not only the first identified Jak-Stat pathway but also other newly found signalling pathways are required for the induction of versatile responses by IFNs. In particular, type I IFNs are inducible by viral infection through the recognition of pathogen-associated molecules by pattern recognition receptors, and the induction of multiple IFN-stimulated genes through the activation of type I IFN signalling confers antiviral and immunomodulatory activities. Any step in this process is often targeted by viruses for their immuno-evasion. The regulatory function of constitutive IFN-alpha/beta signalling has been recognized in terms of its boosting effect on cellular responsiveness in host defence systems. Further comprehensive understanding of IFN signalling may offer a better direction to unravelling the complex signalling networks in the host defence system, and may contribute to their more effective therapeutic applications.

Impairment of IFN-alpha production capacity in patients with hepatitis C virus and the risk of the development of hepatocellular carcinoma

AIM

To determine the utility of interferon (IFN)-alpha production capacity in patients with hepatitis C virus (HCV) infection for the measurement of immuno-surveillance potential and for the early detection of hepatocellular carcinoma (HCC) by investigating the Sendai virus (HVJ) stimulated IFN-alpha production capacity of patients with HCV infection.

METHODS

HVJ stimulated IFN-alpha production was determined in a large number of patients with HCV infection and the development of HCC was monitored for 3 years in patients with liver cirrhosis (LC).

RESULTS

IFN-alpha production capacity decreases gradually with the progression of liver disease from chronic hepatitis (CH) to HCC. A significant correlation between the duration of HCV infection and impaired IFN-alpha production capacity was observed. IFN-alpha production in patients who developed HCC within 3 years was significantly lower than that of patients who remained in LC without developing HCC.

CONCLUSION

Measurement of IFN-alpha production in LC patients may be useful for the early detection of HCC.

Drug abuse, innate immunity and hepatitis C virus

Since its discovery in 1989, hepatitis C virus (HCV) has become a major public health problem. HCV chronically infects an estimated 170 million people worldwide. The seroprevalence of anti-HCV antibody in the United States has been estimated at 1.8%, which corresponds to approximately 4 million people. HCV is the most common chronic blood borne infection in the United States, and the leading cause of liver transplantation in developed countries. Injection drug use is the dominant mode of HCV transmission and accounts for up to 90% of current infections. Opiates and other drug abuse, such as alcohol, have been implicated as cofactors in the pathogenesis of HCV disease. Injection drug use has been the most common risk factor identified in alcoholics with HCV infection. Both opiates and alcohol contribute significantly to morbidity and mortality from HCV disease. These drugs most likely act synergistically to promote the development and progression of HCV disease. However, there is limited information available concerning the interaction of the drug abuse with the host cell innate immunity against HCV infection, which is a major barrier to fundamental understanding of the immunopathogenesis of HCV disease. Therefore, defining the role of the drug abuse in the development of chronic HCV infection is of crucial importance and should provide practical guidance toward the reduction of risk factors that interfere with therapeutic approaches for HCV infection and disease. This review paper focuses on the interplay between drug abuse (opiates and alcohol), innate immunity and HCV in the context of the development of HCV disease.

HypervirulentM. tuberculosisW/Beijing Strains Upregulate Type I IFNs and Increase Expression of Negative Regulators of the Jak-Stat Pathway

The role of type I interferons (IFNs) in the host response to bacterial infections is controversial. Here, we examined the role of IFN-alpha/beta in the murine response to infection with Mycobacterium tuberculosis, using wildtype mice, mice with impaired signaling through the type I IFN receptor (IFNAR), and mice treated to reduce levels of type I IFNs. In this study, we used virulent clinical isolates of M. tuberculosis, including HN878, W4, and CDC1551. Our results indicate that higher levels of type I IFNs are induced by the HN878 and W4 strains. Induction of type I IFNs was associated with lower levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin- 12 (IL-12) and reduced T cell activation, and associated with decreased survival of the mice infected with HN878 or W4 relative to infection with CDC1551. Infection of mice with HN878 and W4 was also associated with relatively higher levels of mRNA for a number of negative regulators of the Jak-Stat signaling pathway, such as suppressors of cytokine signaling (SOCS) 1, 4, and 5, CD45, protein inhibitor of activated Stat1 (PIAS1), protein tyrosine phosphatase nonreceptor type 1 (Ptpn1), and protein tyrosine phosphatase nonreceptor type substrate 1 (Ptpns1). Taken together, these results suggest that increased type I IFNs may be deleterious for survival of M. tuberculosis-infected mice in association with reduced Th1 immunity.

New aspects of IFN-alpha/beta signalling in immunity, oncogenesis and bone metabolism

Although interferons (IFNs) were originally identified as humoral factors that confer an antiviral state upon cells, they have been demonstrated to be multifunctional in a variety of biological systems. The IFN-alpha/beta system modulates not only the cellular immune response to viral and bacterial infections, but also the oncogenic process and bone metabolism. Further studies have revealed additional unique facets of the IFN-alpha/beta system. A weak signal by constitutively produced IFN-alpha/beta is critical not only for the regulation of cellular amplification of IFN-alpha/beta production upon viral infection or the enhancement of signalling by other cytokines, but also for the regulation of adaptive immune responses, such as the enhancement of CD8()+ T cell activation. Furthermore, IFN-beta signalling is critical for the regulation of the bone-resorbing osteoclasts. In this review, we focus on the newly discovered roles of the IFN-alpha/beta system in host defense and bone remodeling, particularly on the functions of the weak IFN-alpha/beta signalling in the context of what we refer to as the "revving-up" model.

Molecular and functional analysis of an interferon gene from the zebrafish, Danio rerio

The interferon (IFN) family consisting of alpha IFN (IFN-alpha), IFN-beta, IFN-omega, IFN-delta, IFN-kappa, and IFN-tau is a large group of cytokines involved in the innate immune response against various microorganisms. Genes for IFN have been cloned from a variety of mammalian and avian species; however, IFN genes from lower-order vertebrates have not been forthcoming. Here, we report the cloning and characterization of the IFN gene from the zebrafish, Danio rerio. Zebrafish IFN (zfIFN) is 185 amino acids in length, with the first 22 amino acids representing a putative signal peptide. Treatment with the known IFN inducer polyinosinic acid-polycytidylic acid (poly[I]-poly[C]) resulted in an increase in zfIFN mRNA transcripts. zfIFN was also able to activate the IFN-inducible Mx promoter when cotransfected with a plasmid containing the zebrafish Mx promoter upstream of a luciferase reporter gene. To demonstrate antiviral activity, zebrafish cells were transfected with zfIFN and challenged with a fish rhabdovirus. A 36% reduction in plaque number was seen in zfIFN-transfected cells, compared to cells transfected with a control vector. Phylogenetic analysis has shown zfIFN to be approximately equally divergent from avian and mammalian IFN, consistent with its origin from an IFN present in the most recent common ancestor of these divergent lineages. A putative IFN from puffer, Fugu rubripes, was also found when zfIFN was used to search the fugu genome database, demonstrating that zfIFN can be used to find additional fish IFN genes. These results demonstrate that zebrafish can be used as an effective model for studying innate immunity and immune response to infectious disease.

Direct evidence that IFN-beta functions as a tumor-suppressor protein

Interferon-beta (IFN-beta) induces aberrant cell cycle progression as well as cytotoxicity and apoptosis. However, the relationship between the cell cycle alteration and the induction of cytotoxicity/apoptosis is unknown. Here, we report the first demonstration that the IFN-beta-induced direct cytotoxic/apoptotic effect can be separated functionally from its cell cycle effect. By using lentiviral transduction, we generated human tumor cells that stably expressed IFN-beta and were resistant to its direct cytotoxic/apoptotic effect. Despite this resistance to apoptosis, these cells showed significant S phase accumulation as measured by both FACS analyses and bromodeoxyuridine (BrdU) incorporation. Although the cells proliferated in the presence of high levels of IFN-beta, they had lost their tumorigenicity in mice. A portion of these cells was observed to undergo a tumor cell-specific senescence. Therefore, our study revealed a direct tumor-suppressor function of IFN-beta. This tumor-suppressor function was independent of IFN-beta-induced direct cytotoxic effect. It was also distinct from the IFN-beta-induced immunologic antitumor response, an indirect effect of IFN-beta. We conclude that the antiproliferative effect on human tumor cells is the collective activities of the direct cytotoxic/apoptotic effect, the cell cycle alteration that occurs as predominantly S phase accumulation, and less frequently other cell cycle effects, such as G(1) arrest, and the promotion of tumor cells into a senescent-like state.

CD4+ T helper cell-independent antitumor response mediated by murine IFN-beta gene delivery in immunocompetent mice

Previously, we provided evidence that adenovirus-mediated interferon-beta (IFN-beta) gene therapy inhibits tumor formation and causes dramatic regression of established tumors in immunodeficient mice. We suggested that local IFN-beta gene therapy with adenoviral vectors could be an effective treatment for cancer. In this report, the actions of murine IFN-beta (MuIFN-beta) gene delivery on both subcutaneous and metastatic tumors were evaluated in syngeneic immunocompetent mice. We found that the antitumor response mediated by MuIFN-beta gene delivery relied on CD8(+) T cells but was completely independent of CD4(+) T cells. In fact, depletion of CD4(+) T cells appeared to enhance the effect on tumor inhibition and animal survival induced by adenovirus-MuIFN-beta gene delivery. Therefore, adenovirus-MuIFN-beta gene therapy can bypass CD4(+) T helper (Th) cells and activate an effective CD8(+) T cell-dependent antitumor immunity in immunocompetent mice. Furthermore, we found that depletion of macrophages but not natural killer (NK) cells suppressed the antitumor response induced by MuIFN-beta gene therapy. These data, together with our previous results, suggest that in the clinical setting, local adenovirus-mediated IFN-beta gene therapy may lead to an efficient and long-lasting eradication of tumors by a direct antitumor effect and via activation of the innate and the adoptive immune systems.

Direct signal transduction via functional interferon-alphabeta receptors in CD34+ hematopoietic stem cells

Affinity purified, freshly isolated CD34+ progenitors were shown to express low levels of type I interferon (IFN) receptors (740 +/- 60 binding sites/cell, K(d) 0.7 +/- 0.04 nM) determined by Scatchard's analysis using a radiolabelled, neutralizing, monoclonal antibody directed against the IFNAR1 chain of the human type I IFN receptor. Treatment of freshly isolated (day 0), highly purified (>95% pure) CD34+ cells with recombinant IFN-alpha resulted in rapid tyrosine phosphorylation and activation of STAT1, Tyk2 and JAK1 as shown by Western immunoblotting. Similarly, IFN treatment was shown by confocal microscopy to result in rapid nuclear localization of the transcription factors IRF1 and STAT2, demonstrating the presence of functional IFN receptors on freshly isolated (day 0) CD34+ cells. The number of specific type I IFN receptor binding sites expressed on hematopoietic progenitor cells increased to some 1440 +/- 40 per cell after 11 days of cultivation of CD34+ cells in vitrosuggesting that receptor expression increases with cell differentiation. IFN-mediated signal transduction and the inhibitory effect of IFN-alpha on 7 or 14 days CFU-GM and BFU-E colony formation was abrogated in the presence of the anti-IFNAR1 mAb, indicating that IFN-alpha acts directly on the proliferation of human hematopoietic progenitor cells via receptor activated signal transduction without excluding the induction of other cytokines or growth factors by residual accessory cells.

Endogenous type I interferons as a defense against tumors

We have reviewed the experimental results which indicate that endogenous type I interferon (IFN) present either constitutively or possibly induced by the tumor plays an important role in limiting the development of transplantable tumors in mice. Thus, treatment with potent polyclonal neutralizing antibodies to IFN alpha/beta markedly enhanced the subcutaneous growth, invasiveness and metastases of xenogeneic tumor cells (uninfected or infected with RNA or DNA viruses) in athymic nude mice; enhanced the intraperitoneal transplantability of six different syngeneic murine tumors in three strains of immunocompetent mice; and completely abrogated the resistance of allogeneic C57Bl/6 (H-2(b)) or C3H (H-2(k)) mice to the multiplication of Friend erythroleukemia cells (H-2(d)) in the liver and spleen resulting in the death of most mice. The mechanisms by which mice respond to the injection of relatively few tumor cells appear to be multiple, to depend on the site of tumor growth, to occur early and prior to an immunologic response. Endogenous type I IFN appears to constitute an essential component of these defense mechanisms enabling the host to restrict tumor growth.

The interferon-alpha/beta system in antiviral responses: a multimodal machinery of gene regulation by the IRF family of transcription factors

The efficient induction of interferons alpha and beta (IFN-alpha/beta) in virus-infected cells is central to the antiviral response of a host and is regulated mainly at the level of gene transcription. Once produced, IFN-alpha/beta transmit signals to the cell interior via a specific receptor complex to induce an antiviral response. Recently, the auto-amplification mechanism of the IFN-alpha/beta system that follows viral infection has been identified. This mechanism is mediated by transcription factors of the IFN regulatory factor family and, in fact, may have evolved to render the system more robust in antiviral responses.

Constitutive IFN-alpha/beta signal for efficient IFN-alpha/beta gene induction by virus

Efficient IFN-alpha/beta gene induction in virus-infected cells is an event central to innate immunity, in which the transcription factor IRF-7 plays a critical role together with IRF-3. Unlike IRF-3, IRF-7 is short-lived and its gene expression is dependent on IFN-alpha/beta signalling; hence, the signal-dependent enhancement of IRF-7 gene induction during viral infection is essential for positive-feedback regulation of IFN-alpha/beta gene induction. Here, we provide evidence that constitutive, IRF-3/IRF-7-independent production of IFN-alpha/beta in uninfected cells is critical for setting the IRF-7 expression levels, determining whether or not the positive-feedback mechanism will operate effectively upon viral infection. In fact, spleen cells are more dependent than fibroblasts on this mechanism; the IFN-alpha/beta gene induction is impaired more severely by blocking the IRF-7 induction pathway than by introducing an IRF-3 null mutation. Thus, the constitutive IFN-alpha/beta signal provides a foundation for the IRF-7-mediated enhancement of its own production in response to virus infection.

A weak signal for strong responses: interferon-alpha/beta revisited

Biological systems have acquired adaptability and robustness against rapid environmental changes. A typical example is the immune system, which eradicates invading pathogens such as viruses. Interferons alpha and beta, which are produced in response to viral infection, are essential components of this system but are also produced at low levels in the absence of infection. What is the purpose of the constitutive weak interferon-alpha/beta signal?

Inhibitory activity of constitutive nitric oxide on the expression of alpha/beta interferon genes in murine peritoneal macrophages

We investigated the role of the constitutive nitric oxide (NO) in the expression of interferon (IFN) genes in mouse peritoneal macrophages (PM). The treatment of PM with L-arginine-N(G)-amine (AA), a potent inhibitor of NO-producing enzymes, resulted in a marked accumulation of IFN-alpha4 mRNA and, to a minor extent, of IFN-beta mRNA. In contrast, the expression of IFN-gamma mRNA, as well as tumor necrosis factor alpha and interleukin-6 mRNA, was not affected. Furthermore, a remarkable increase in the expression of the IFN regulating factor 1 (IRF-1), but not of IRF-2, mRNA was detected in AA-treated PM. To investigate whether the AA-induced activation of the IFN system correlates with the production and antiviral activity of IFN, the extent of encephalomyocarditis virus (EMCV) replication was monitored in AA-treated PM with respect to control cultures. AA treatment strongly inhibited, in a dose-dependent manner, EMCV yields in PM. Likewise, similar results were obtained by the addition of the NO-scavenger carboxyphenyl-tetramethylimidazoline-oxyl-oxide. In addition, inhibition of NO synthesis by N(G)-mono-methyl-L-arginine in PM strongly decreased virus replication in coculture of PM and EMCV-infected L929 cells, whereas no antiviral effect was observed in L929 cells alone. Moreover, the AA-mediated antiviral activity was abrogated in the presence of antibody to IFN-alpha/beta, whereas antibody to IFN-gamma was completely ineffective. Taken together, these results indicate that low levels of NO, constitutively released by resting PM, negatively regulate the expression and activity of IFN-alpha/beta in PM. We suggest that NO acts as a homeostatic agent in the regulation of IFN pathway expression in macrophages.

Oromucosal interferon therapy: marked antiviral and antitumor activity

Oromucosal administration of murine interferon-alpha/beta (IFN-alpha/beta) or individual recombinant species of murine IFN-alpha, IFN-beta, or IFN-gamma or recombinant human IFN-alpha1-8, which is active in the mouse, exerted a marked antiviral activity in mice challenged systemically with a lethal dose of encephalomyocarditis virus (EMCV), vesicular stomatitis virus (VSV), or varicella zoster virus (VZV). The effects observed were dose dependent and similar in magnitude to those observed following parenteral administration of the same dose of IFN. No antiviral activity was observed after oromucosal administration of murine IFN-alpha/beta in animals in which the IFN receptor had been inactivated by homologous recombination. In contrast to parenteral treatment, oromucosal IFN therapy was found to be ineffective when IFNs were administered before virus infection. Oromucosal administration of IFN-alpha also exerted a marked antitumor activity in mice injected i.v. with highly malignant Friend erythroleukemia cells or other transplantable tumors, such as L1210 leukemia, which has no known viral etiology, the EL4 tumor, or the highly metastatic B16 melanoma. These results show that high doses of IFN can be administered by the oromucosal route apparently without ill effect, raising the possibility that the oromucosal route will prove to be an effective means of administering high doses of IFN that are clinically effective but poorly tolerated.

Importance of cyclophosphamide-induced bystander effect on T cells for a successful tumor eradication in response to adoptive immunotherapy in mice

Cyclophosphamide (CTX) increases the antitumor effectiveness of adoptive immunotherapy in mice, and combined immunotherapy regimens are now used in some clinical trials. However, the mechanisms underlying the synergistic antitumor responses are still unclear. The purpose of this study was (a) to evaluate the antitumor response to CTX and adoptive immunotherapy in mice bearing four different syngeneic tumors (two responsive in vivo to CTX and two resistant); and (b) to define the mechanism(s) of the CTX-immunotherapy synergism. Tumor-bearing DBA/2 mice were treated with a single injection of CTX followed by an intravenous infusion of tumor-immune spleen cells. In all the four tumor models, a single CTX injection resulted in an impressive antitumor response to the subsequent injection of spleen cells from mice immunized with homologous tumor cells independently of the in vivo response to CTX alone. Detailed analysis of the antitumor mechanisms in mice transplanted with metastatic Friend leukemia cells revealed that (a) the effectiveness of this combined therapy was dependent neither on the CTX-induced reduction of tumor burden nor on CTX-induced inhibition of some putative tumor-induced suppressor cells; (b) the CTX/immune cells' regimen strongly protected the mice from subsequent injection of FLC, provided the animals were also preinoculated with inactivated homologous tumor together with the immune spleen cells; (c) CD4(+) T immune lymphocytes were the major cell type responsible for the antitumor activity; (d) the combined therapy was ineffective in mice treated with antiasialo-GM1 or anti-IFN-alpha/beta antibodies; (e) spleen and/ or bone marrow cells from CTX-treated mice produced soluble factors that assisted in proliferation of the spleen cells. Altogether, these results indicate that CTX acts via bystander effects, possibly through production of T cell growth factors occurring during the rebound events after drug administration, which may sustain the proliferation, survival, and activity of the transferred immune T lymphocytes. Thus, our findings indicate the need for reappraisal of the mechanisms underlying the synergistic effects of CTX and adoptive immunotherapy, and may provide new insights into the definition of new and more effective strategies with chemotherapy and adoptive immunotherapy for cancer patients.

The neglected role of type I interferon in the T-cell response: implications for its clinical use

Originally described as an antiviral substance, type I interferon (IFN) was subsequently shown to exert multiple biological effects and is now the most frequently used cytokine in the treatment of some viral and neoplastic diseases. Although early studies described various effects on the immune system, the role of type I IFN as an immunoregulatory molecule has long been neglected. Here, Filippo Belardelli and Ion Gresser summarize recent experimental results on the interactions of type I IFN with T cells, which may prove important in its use in patients.