Interferon inhibits the generation of allospecific suppressor T lymphocytes

APC activation by IFN-alpha decreases regulatory T cell and enhances Th cell functions

Type I IFNs are central to a vast array of immunological functions. Their early induction in innate immune responses provides one of the most important priming mechanisms for the subsequent establishment of adaptive immunity. The outcome is either promotion or inhibition of these responses, but the conditions under which one or the other prevails remain to be defined. The main objective of the current study was to determine the involvement of IFN-alpha on murine CD4(+)CD25(-) Th cell activation, as well as to define the role played by this cytokine on CD4(+)CD25(+) regulatory T (Treg) cell proliferation and function. Although IFN-alpha promotes CD4(+)CD25(-) Th cells coincubated with APCs to produce large amounts of IL-2, the ability of these cells to respond to IL-2 proliferative effects is prevented. Moreover, in medium supplemented with IFN-alpha, IL-2-induced CD4(+)CD25(+) Treg cell proliferation is inhibited. Notably, IFN-alpha also leads to a decrease of the CD4(+)CD25(+) Treg cell suppressive activity. Altogether, these findings indicate that through a direct effect on APC activation and by affecting CD4(+)CD25(+) Treg cell-mediated suppression, IFN-alpha sustains and drives CD4(+)CD25(-) Th cell activation.

Autoimmune Hepatitis Induced by Interferon Beta Therapy in a Patient with Multiple Sclerosis: A Case Report

Objective:

To report a case of a woman who had multiple sclerosis and developed autoimmune hepatitis (AIH) induced by interferon beta therapy.

Case Summary:

A 35–year-old woman with multiple sclerosis was being treated with interferon beta when she presented with fatigue and jaundice. Liver biochemistry testing revealed acute hepatitis (alanine and aspartate aminotransferase values >10 times the upper limit of normal) that was histologically consistent with AIH. Our patient had a score of 9 on the Roussel Uclaf Causality Assessment Method scale, indicating a high probability that hepatotoxicity in this case was related to interferon beta therapy. The patient had spontaneous clinical and biochemical improvement after stoppage of treatment. However, when she resumed interferon beta therapy, derangement of liver function reappeared, which again responded well to discontinuation of interferon.

Discussion:

Interferons can induce many autoimmune diseases due to their immunomodulatory effects. Autoimmune thyroid diseases and, to a lesser extent, skin and pulmonary involvement, are frequently reported during interferon alfa treatment for chronic hepatitis C. Several different forms of hepatotoxicity have also been described with interferon alfa and beta therapy, but few cases of AIH induced by interferon are reported in the literature. AIH has been described in association with interferon alfa therapy; however, this association with interferon beta therapy is extremely rare, and only a handful of cases have been described. Moreover, reports of previous cases were not rechallenged with the same medication, thereby failing to demonstrate firm evidence of causality. This is the first report of the disease reappearing upon drug rechallenge. In addition, we have shown that interferon-induced AIH can be suitably treated by drug withdrawal rather than by institution of steroid therapy.

Conclusions:

Practitioners need to be aware of the potential complication of AIH induced by interferon beta; this condition occurs independently of the typically benign enzyme elevations frequently reported with this drug.

Dendritic cells in cytomegalovirus infection: viral evasion and host countermeasures

Human cytomegalovirus (HCMV) is a beta-herpesvirus that infects the majority of the population during early childhood and thereafter establishes life-long latency. Primary infection as well as spontaneous reactivation usually remains asymptomatic in healthy hosts but can, in the context of systemic immunosuppression, result in substantial morbidity and mortality. HCMV counteracts the host immune response by interfering with the recognition of infected cells. A growing body of literature has also suggested that the virus evades the immune system by paralyzing the initiators of antiviral immune responses--the dendritic cells (DCs). In the current review, we discuss the effects of CMV (HCMV and murine CMV) on various DC subsets and the ensuing innate and adaptive immune responses. The impact of HCMV on DCs has mainly been investigated using monocyte-derived DCs, which are rendered functionally impaired by infection. In mouse models, DCs are targets of viral evasion as well, but the complex cross-talk between DCs and natural killer cells has, however, demonstrated an instrumental role for DCs in the control and clearance of viral infection. Fewer studies address the role of peripheral blood DC subsets, plasmacytoid DCs and CD11c+ myeloid DCs in the response against HCMV. These DCs, rather than being paralyzed by HCMV, are largely resistant to infection, mount a vigorous first-line defense and induce T-cell responses to the virus. This possibly provides a partial explanation for an intriguing conundrum: the highly efficient control of viral infection and reactivation in immunocompetent hosts in spite of multi-layered viral evasion mechanisms.

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.

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.

Improving the in vitro antigen specific T cell proliferation assay: the use of interferon-alpha to elicit antigen specific stimulation and decrease bystander proliferation

The measurement of the proliferative response of primed T cells to an antigenic stimulus (lymphocyte transformation assay: LTT) is commonly used for determining T cell immune responsiveness. However, the ratio between the spontaneous and the antigen-triggered response (stimulation index) is frequently quite low (<3-5) making the interpretation difficult. We modified the assay by the addition of interferon-alpha and the use of fresh autologous serum instead of human AB pool serum. These measures significantly enhanced the stimulation index following stimulation with tetanus toxoid, Candida albicans and tick-borne encephalitis (TBE) viral antigen in studies of sensitized patients. There was no concomitant increase in false positive results. Kinetic studies showed a reduced nonspecific background proliferation of non-stimulated cultures particularly between days 4 and 6 of culture. Furthermore, the positive effect of interferon-alpha were confirmed in studies of patients with contact allergy to nickel and gold. We conclude that this modified form of proliferation assay significantly increases the signal to noise ratio which can be attained. This may be of particular value when looking at T cell responses in immunocompromised patients or in diagnostic attempts to detect very low frequencies of antigen-specific T cells.

Cyclophosphamide induces type I interferon and augments the number of CD44hi T lymphocytes in mice: implications for strategies of chemoimmunotherapy of cancer

In a previous study, we reported that a single injection of cyclophosphamide (CTX) in tumor-bearing mice resulted in tumor eradication when the animals were subsequently injected with tumor-sensitized lymphocytes. Notably, CTX acted by inducing bystander effects on T cells, and the response to the combined CTX/adoptive immunotherapy regimen was inhibited in mice treated with antibodies to mouse interferon (IFN)–/β. In the present study, we have investigated whether CTX induced the expression of type I IFN, and we have characterized the CTX effects on the phenotype of T cells in normal mice. CTX injection resulted in an accumulation of type I IFN messenger RNA in the spleen of inoculated mice, at 24 to 48 hours, that was associated with IFN detection in the majority of the animals. CTX also enhanced the expression of the Ly-6C on spleen lymphocytes. This enhancement was inhibited in mice treated with anti–type I IFN antibodies. Moreover, CTX induced a long-lasting increase in in vivo lymphocyte proliferation and in the percentage of CD44hiCD4+ and CD44hiCD8+T lymphocytes. These results demonstrate that CTX is an inducer of type I IFN in vivo and enhances the number of T cells exhibiting the CD44hi memory phenotype. Since type I IFN has been recently recognized as the important cytokine for the in vivo expansion and long-term survival of memory T cells, we suggest that induction of this cytokine may explain at least part of the immunomodulatory effects observed after CTX treatment. Finally, these findings provide a new rationale for combined treatments with CTX and adoptive immunotherapy in cancer patients.

Autoimmunity induced by interferon-alpha therapy for chronic viral hepatitis

Type I interferons, which are mostly alpha-interferons (either as single agents or in combination with antiviral drugs), are currently the standard therapy for chronic viral hepatitis B, B/D, and C. Side-effects are not uncommon and include exacerbation of pre-existing autoimmune disorders or the de novo induction of autoimmunity. These adverse effects are attributed to the immunomodulatory properties of type I interferons, and should be distinguished from autoimmunity associated with chronic viral hepatitis in which interferon treatment may indeed be beneficial. The major autoimmune side-effects of interferon therapy for chronic viral hepatitis are thyroid or liver disease. Therefore, screening for thyroid antibodies and auto-antibodies indicative of autoimmune hepatitis both before, during, and after interferon therapy is strongly recommended. The presence of high concentrations of thyroid auto-antibodies or antibodies associated with autoimmune hepatitis can be contraindicative to interferon therapy. However, treatment is not contraindicated in viral hepatitis (in particular chronic hepatitis C) associated with autoimmune phenomena--including low-titer thyroid antibodies or other non-organ specific auto-antibodies. If interferon-induced autoimmunity occurs, the necessity of therapy has to be balanced carefully against the risks of autoimmune disease. Further research is needed to identify the factors which determine susceptibility to interferon-associated autoimmunity in individual patients.

Type I interferons keep activated T cells alive

Antigen injection into animals causes antigen-specific T cells to become activated and, rapidly thereafter, die. This antigen-induced death is inhibited by inflammation. To find out how inflammation has this effect, various cytokines were tested for their ability to interfere with the rapid death of activated T cells. T cells were activated in vivo, isolated, and cultured with the test reagents. Two groups of cytokines were active, members of the interleukin 2 family and the interferons (IFNs) alpha and beta. This activity of IFN-alpha/beta has not been described previously. It was due to direct effects of the IFNs on the T cells and was not mediated by induction of a second cytokine such as interleukin 15. IFN-gamma did not slow the death of activated T cells, and therefore the activity of IFN-alpha/beta was not mediated only by activation of Stat 1, a protein that is affected by both classes of IFN. IFN-alpha/beta did not raise the levels of Bcl-2 or Bcl-XL in T cells. Therefore, their activity was distinct from that of members of the interleukin 2 family or CD28 engagement. Since IFN-alpha/beta are very efficiently generated in response to viral and bacterial infections, these molecules may be among the signals that the immune system uses to prevent activated T cell death during infections.

Type I interferons

Type I interferons (IFNs) constitute a family of structurally related proteins that are all derived from the same ancestral gene and act on a common cell-surface receptor. Contrary to many other cytokines, the production of type I IFNs is not a specialized function, and all cells in the organism can produce them, usually as a result of induction by viruses, via the formation of double-stranded RNA. Type I IFNs are indeed responsible for the first line of defense during virus infection and act through the induction of a great number of proteins. Of these, at least thirty have been characterized, and there are probably many more. In addition to their direct antiviral effect, type I IFNs exert a wide variety of other activities, such as for example the induction of various cytokines and the stimulation of different effector cells of the immune system. Due to these pleiotropic effects, recombinant interferons are used in the clinic to treat a variety of diseases, among which cancer, viral hepatitis and multiple sclerosis.

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.

Successful immunotherapy of the highly metastatic murine ESb lymphoma with sensitized CD8+ T cells and IFN-alpha/beta

Daily IFN-alpha/beta therapy was totally ineffective in inhibiting the development of visceral metastases in DBA/2 mice injected i.v. with the ESb lymphoma regardless of the number of tumor cells injected. The finding that IFN-alpha/beta therapy increased the survival time of ESb-immunized mice rechallenged with ESb cells suggested that cooperation between the immune system and IFN-alpha/beta was important. Adoptive transfer of Esb-immune spleen cells (but not normal cells) together with IFN-alpha/beta treatment did inhibit the development of ESb metastases in immunocompetent DBA/2 mice. Either treatment alone was ineffective. The anti-metastatic effect was specific for the ESb lymphoma as spleen cells from ESb-immunized mice together with IFN-alpha/beta treatment did not inhibit the development of metastases in mice challenged with IFN-alpha/beta-resistant 3C18 FLC. Depletion of CD8+ T cells (but not CD4+ T cells or B lymphocytes) prior to transfer eliminated the protective effect of ESb-immune splenocytes in IFN-alpha/beta-treated mice. As few as 1 x 10(6) ESb-immune spleen cells highly enriched for CD8+ cells increased the survival time of IFN-alpha/beta-treated ESb-challenged DBA/2 mice. The combined therapy of ESb-specific immune cells and IFN-alpha/beta resulted in long-term immunity to this tumor.

Sensitized T lymphocytes render DBA/2 beige mice responsive to IFN alpha/beta therapy of Friend erythroleukemia visceral metastases

Interferon alpha/beta (IFN alpha/beta) is highly effective in inhibiting the development of Friend erythroleukemia cell (FLC) visceral metastases in DBA/2 mice injected intravenously (i.v.) with FLC, but does not protect FLC-injected DBA/2 beige (bg/bg) mice. Use of IFN alpha/beta-resistance FLC indicated that IFN was acting through host mechanisms in DBA/2 mice and thus pointed to a defect in some host mechanism in bg/bg mice essential for IFN's anti-metastatic action. We undertook experiments to restore in bg/bg mice the marked anti-FLC metastatic effect of IFN alpha/beta observed in DBA/2 and +/bg mice. Adoptive transfer of spleen cells from normal syngeneic mice to IFN-treated bg/bg mice was ineffective, but the transfer of splenic T lymphocytes from FLC-immunized DBA/2 or +/bg mice markedly increased the survival time of FLC-injected bg/bg mice provided that these mice were also treated with IFN alpha/beta. Neither treatment alone resulted in an increase in survival time. As few as 1 x 10(7) immune spleen cells were effective in IFN-treated FLC-injected bg/bg mice. The T-cell immune response to FLC of bg/bg mice was diminished compared with that of +/bg mice. Likewise, only combination therapy of immune spleen cells and IFN alpha/beta resulted in an increased survival time of ESb-lymphoma-injected bg/bg mice. Our results indicate the essential participation both of T-cell-mediated immune mechanisms and of IFN alpha/beta in the inhibition of FLC visceral metastases.

The influence of adjuvants on the generation of autoantibody and specific suppression in rat erythrocyte-immunized mice

A number of adjuvants were investigated for their ability to modulate either the autoimmune response induced in mice by immunization with rat erythrocytes (RRBC) or the ability of RRBC-primed spleen cells to suppress the induction of anti-red cell autoimmunity in recipient mice. The inability of the agents used to do so is discussed on the background of models used to explain the generation of suppression in this system.

Effect of recombinant human interferon-alpha in vitro and in vivo on mitogen-induced lymphocyte blastogenesis in cats

The effect of recombinant human interferon-alpha (rHuIFN-alpha) in vitro and in vivo on mitogen-induced lymphocyte blastogenesis was evaluated in specific-pathogen-free cats. Pre-incubation of isolated feline peripheral blood lymphocytes (PBL) in vitro with either 10(4) or 10(3) International Units (U) of rHuIFN-alpha for 24 h significantly suppressed (P less than 0.001 and 0.01, respectively) blastogenic responses to the phytomitogens concanavalin A (Con A) and pokeweed mitogen (PWM). Lower doses of IFN (range, 10-10(-3) U/ml) neither suppressed nor enhanced mitogenesis. In the absence of phytomitogens, incubation of PBL with 10(4) - 10(2) U (P less than 0.001) or 10 U (P less than 0.05) of rHuIFN-alpha/ml resulted in a significant decrease in incorporation of [methyl-3H] thymidine into newly synthesized cellular DNA. Cultures of PBL exposed continuously for 4 days to rHuIFN-alpha doses of 10(4) U/ml or less did not demonstrate specific reductions in cell viability, indicating that the observed antiproliferative actions of IFN apparently were independent of any direct cytotoxic effects. To investigate the dose-response effects of rHuIFN-alpha in vivo on lymphocyte blastogenesis, individual groups of cats were evaluated on 3 consecutive days before and then 24 h after each cat was inoculated intramuscularly with either a high dose (10(6) U/kg), moderate dose (10(4) U/kg), or a relatively low dose (10(2) U/kg) of rHuIFN-alpha. Cats inoculated with 10(6) U of rHuIFN-alpha/kg had significantly reduced (P = 0.037) blastogenic responses to Con a at 24 h postinoculation compared to preinoculation values; mean PWM responses were also decreased, but this effect was not statistically significant. In contrast, inoculation of cats with either 10(4) or 10(2) U of rHuIFN-alpha/kg significantly enhanced (P = 0.05 or 0.008, respectively) Con A-induced blastogenesis and had no discernible effect on PWM responses. These findings suggest that very high doses of rHuIFN-alpha given parenterally may be associated with suppression of certain T-cell responses in cats; conversely, much lower doses may be immunoenhancing.

Interferons and autoimmunity

Autoimmunity can be accelerated in several genetically prone murine models and can even be induced in normal mice by treatment with interferon (IFN) or IFN-inducers. Several cases of IFN-induced autoimmune disease in humans also have been observed; however, more striking is the fact that some of the clinical manifestations in autoimmune diseases and many of the immunological aberrations can be mediated or enhanced by IFN. The finding of high levels of circulating IFN in many patients may be highly significant in that respect, and the characterization of the predominant type of IFN as an unusual acid-labile IFN-alpha may indicate an infectious etiologic agent in autoimmunity, since this peculiar IFN was mostly associated with viral infections in vivo or in vitro. The induction of MHC class II antigens on previously HLA-DR or Ia negative cells appears to be caused primarily by IFN-gamma and may have a central role in the pathogenesis of autoimmunity in susceptible individuals. Such aberrant HLA-DR expression on nonlymphoid cells can be detected early in the disease in the target organs of many varied autoimmune conditions and may trigger a cascade of self-directed, uncontrolled immune response in conjunction with other factors.

Selective up-regulation by interferon-gamma of surface molecules of the Ly-6 complex in resting T cells: the Ly-6A/E and TAP antigens are preferentially enhanced

Surface molecules encoded by the murine Ly-6 locus can transduce triggering signals in T cells and thus may play important roles in T cell function. Previously, we found that Ly-6 molecules are up-regulated by interferon (IFN)-alpha/beta in resting T cells. Here, we examined the possible influence of IFN-gamma on these molecules. Purified T cells from C57BL/6 (Ly-6.2) and BALB/c (Ly-6.1) mice were incubated in vitro with recombinant murine IFN-gamma and the expression of Ly-6 antigens was measured by flow cytofluorometry. It was found that both Ly-6A/E and T cell-activating protein (TAP) molecules are markedly enhanced while Ly-6C is less affected. Under the same conditions, other T cell surface molecules showed no or marginal changes. The effect of IFN-gamma on Ly-6A/E and TAP expression reached a maximum with as little as 10 U/ml and required only 18-24 h of incubation. Moreover, the enhancement of Ly-6A expression induced by IFN-gamma was stable for at least 5 days. Analysis of T cell subsets further revealed that IFN-gamma-induced augmentation of Ly-6A (C57BL/6 mice) involves both Lyt-2+ and L3T4+ cells while the increase of Ly-6E (BALB/c mice) is more pronounced in Lyt-2+ cells. The functional consequence of these phenotypic alterations was evaluated by studying the mitogenic responses of T cells to antibody-mediated Ly-6 cross-linking in the presence of phorbol myristate acetate. Pretreatment of resting T cells with IFN-gamma dramatically increased the responses to anti-Ly-6A and anti-Ly-6E monoclonal antibodies. IFN-gamma treatment also boosted the stimulation induced by anti-TAP monoclonal antibody when this stimulation was performed under suboptimal conditions. Therefore, IFN-gamma selectively up-regulates the Ly-6A/E and TAP activation pathways in resting T cells. We speculate that this effect may contribute to the immunoregulatory activities of IFN-gamma.

Alpha interferon in the treatment of hematologic malignancies

The interferons are an important first member of a family of biologic response-modifiers used in treating human malignancies. Activities associated with the interferons include inhibition of viral replication, influence on cellular protein production, direct antiproliferative effects, and a variety of modulatory effects on the immune response. These regulatory functions of interferon underlie the interest in its use as an anticancer agent. Alpha interferon is the most extensively studied interferon species. Although antitumor activity has been seen both in vitro and in vivo in some solid malignancies, the most impressive responses have occurred in the hematologic malignancies. More than 90 percent of patients with hairy cell leukemia have a sustained recovery of their peripheral blood cell counts with alpha interferon therapy. Approximately 50 percent of patients with low-grade non-Hodgkin's lymphoma and cutaneous T cell lymphoma demonstrate a response to alpha interferon. More than 80 percent of patients with chronic myelogenous leukemia have a response to alpha interferon, and in one study, nearly half of the patients with response had complete suppression of the Philadelphia chromosome clone on at least one examination. Ongoing clinical trials are addressing such issues as optimal dosage, duration of alpha interferon therapy, and combinations of alpha interferon with other biologic agents, chemotherapy drugs, and radiation.

Effects of interferon on the lymphocyte subset in the blood and lymphoid organs in mice

The effects of mouse interferon-alpha/beta (MuIFN) or poly(I):poly(C) injection on the lymphocytes in the blood, thymus, and spleen of C3H/HeN mice were examined. A single injection of MuIFN (2 X 10(6) to 2 X 10(7) IU/kg of MuIFN) or poly(I):poly(C) (0.12-1.2 mg/kg) caused a significant lymphocytopenia without any evidence of direct cytotoxic effects on lymphocytes in the blood or lymphoid organs, a significant decrease in the number of T cells both in the thymus and spleen along with a significant increase in the number of non-T cells in the splenic white pulp, and a differential decrease in the number of blood T-cell subsets ("suppressor/cytotoxic" subset was decreased continuously whereas "helper" subset only transiently). The differential effect on T-cell subsets could explain the complicated effects of IFN on the cell-mediated immune response.

A sensitive radioimmunoassay for alpha-interferon: circulating alpha-interferon-like substance in the plasma of healthy individuals and rheumatoid arthritis patients

A radioimmunoassay for circulating alpha-interferon (IFN alpha) has been developed using lymphoblastoid IFN alpha. The assay was specific for IFN alpha, and did not cross-react with IFN beta, IFN gamma, or ACTH, while it was specifically inhibited by recombinant IFN alpha. The radioimmunoassay (y) correlated linearly with the virus inhibition assay (x), with a regression line of y on x of y = 0.659x + 245 (u) (P less than 0.01). alpha-Interferon-like substance (IFN alpha-LS) was extracted and concentrated from plasma either by silicic acid or by antibody immunoadsorption. Serial dilutions of plasma and extracted samples of plasma showed dilution curves identical to those of standard IFN alpha, suggesting the presence of endogenous IFN alpha in human plasma. The circulating IFN alpha-LS of healthy individuals aged 20 to 45 was 0.207 +/- 0.055 ng/ml in males (n = 48) and 0.172 +/- 0.076 ng/ml in females (n = 34). Gel filtration studies on a Sephadex G-75 column suggested that circulating IFN alpha-LS exists in a fragmented form, inactive in virus inhibition assays, in the plasma of healthy individuals. The finding may help explain why biological IFN alpha is often undetectable in the plasma of healthy donors, yet is detectable by radioimmunoassay. Circulating IFN alpha-LS in the plasma of healthy individuals declined gradually with age. IFN alpha-LS was significantly decreased in the plasma of rheumatoid arthritis patients, when compared with the value found in the age and sex-matched healthy controls and in osteoarthritis patients (P less than 0.0001). The decrease was related neither to treatment nor to disease activity. IFN alpha-LS was, however, not decreased in the plasma of vasculitis patients. Decreased IFN alpha-LS in rheumatoid arthritis may be important from pathogenetic and therapeutic standpoints.

Treatment of resting T lymphocytes with interferon-alpha/beta augments their proliferative response to activation signals delivered through their surface Ly-6 antigen

Although the exact significance of Ly-6 antigens is unknown, recent evidence suggests they may provide an important alternative pathway for murine T-cell activation. Thus, Shevach et al. (1986, Fed. Proc. 45, 1131) discovered that cross-linking of Ly-6 antigens on the cell surface acts in concert with phorbol myristate acetate to trigger mitogenesis in T cells. Previously, we reported that surface expression of Ly-6 antigens on T cells is markedly increased following exposure to interferon-alpha/beta (IFN-alpha/beta). The purpose of the present work was to determine the effect of IFN-induced Ly-6 enhancement on Ly-6-mediated T-cell stimulation. Purified T cells were incubated in vitro for 1-27 hr with various doses (10-10(4) units/ml) of IFN-alpha/beta. This was found to result in various degrees of augmentation of the proliferative responses of these T cells to stimulation through their Ly-6 antigen. Surprisingly, while maximal enhancement of Ly-6 expression occurred only after the longest pulses with the highest IFN concentrations, treatment with as little as 100 units IFN/ml for 12 hr was sufficient to induce a dramatic (25-fold) and nearly maximal enhancement of proliferation. This high sensitivity to IFN-alpha/beta of the Ly-6 pathway of T-cell activation led us to speculate that this pathway may play a role in the immunomodulatory activities of IFN-alpha/beta.

Interferon-alpha/beta enhances the expression of Ly-6 antigens on T cells in vivo and in vitro

Interferons (IFN) have been shown to modulate the expression of a number of cell surface antigens on macrophages and lymphocytes. Because such phenotypic alterations may be involved in the functional effects of IFN, it appears important to characterize further these alterations. In the present work, we evaluated the response to IFN of Ly-6-encoded molecules on murine T cells. Two types of Ly-6 antigens, Ly-6A and Ly-6C, normally present on minor subsets of mature T cells were studied. It was found that in vivo treatment of mice with the IFN inducer poly(I . C) or with purified IFN-alpha/beta resulted two days later in augmented expression of these antigens. Purified T cells cultured in vitro for 2 days in the presence of 5% serum from poly(I . C)-treated mice or of 10(4) units/ml IFN-alpha/beta also displayed dramatically increased (4-12-fold) amounts of Ly-6 antigens. Under the same conditions, the T cell markers Thy-1, Ly-1, Lyt-2 and MT4 were unaffected or slightly diminished while surface expression of H-2 or beta 2-microglobulin antigens was increased by only 10-36%. Therefore, poly(I . C)-induced or purified IFN interacts with resting T cells to selectively enhance Ly-6 antigen expression. This phenomenon was found to correlate functionally with increased proliferative response of the T cells, in presence of phorbol myristate acetate, to anti-Ly-6 antibodies cross-linked on their surface. Enhancement of Ly-6 antigen expression on T cells may thus play a role in IFN-mediated immunoregulation.

Inhibitory effects of interferon-gamma on the T suppressor cell circuit in contact sensitivity

The effects of a partially purified, splenocyte-derived murine interferon (MuIFN-gamma N) and a recombinant IFN-gamma (MuIFN-gamma R) on the T suppressor pathway and on the T effector cells of delayed type hypersensitivity were investigated in a 2,4-dinitrofluorobenzene contact sensitivity model. Various T cell subpopulations, suppressor T cells of afferent and efferent types, and an auxiliary T suppressor cells as well as a T effector cell of delayed type hypersensitivity were induced and the functions assessed in transfer experiments. Confirming the results of earlier experiments obtained with IFN-alpha, beta, the MuIFN-gamma N preparation and the rec. MuIFN-gamma R: enhanced the decreased response in animals sensitized with an antigen overload to an optimal response; inhibited the afferent-acting T suppressor cell in vivo and in vitro; inhibited the Ts-eff response; blocked the auxiliary T suppressor cell response after intravenous injection to recipients of Ts-eff cells on day 0 and 1; and did not suppress the activity of the T effector cell of delayed type hypersensitivity in vivo and in vitro (the MuIFN-gamma R was not tested). We conclude that IFN-gamma preferentially inhibited the T suppressor cell circuit of contact allergy. These results are similar to our observations on the inhibitory effects of a pure interferon-alpha, beta on the regulatory T suppressor cell circuit in contact allergy. Selective suppression of different T subpopulations by IFN-gamma may be an important regulatory mechanism in delayed type hypersensitivity.

Interferon activity and its characterization in the sera of patients with head and neck cancer

The interferon (IFN) assay of the sera from the 40 patients with head and neck cancer was performed by the plaque-reduction assay with vesicular stomatitis virus in FL cells derived from human amniotic membrane. The patients mainly had Stage III or IV lesion without distant metastasis, and previously had not received any cancer therapy. All of the patients were histologically diagnosed as squamous cell carcinoma. When the serum IFN activity was characterized by acid treatment, significant increases of IFN-alpha/beta/gamma (n = 24, P less than 0.05) and acid-labile IFN (n = 24, P less than 0.001), and significant decrease of acid-stable IFN (n = 24, P less than 0.001) in the cancer patients of 50-to-79-year age group were found, as compared with those in the normal controls of the same age group (n = 20). When IFN titers including various immunologic parameters of the patients and normal controls were simultaneously assayed prior to the beginning of the cancer therapy, the titers of IFN-alpha/beta/gamma, acid-stable IFN, and acid-labile IFN were significantly correlated with some immunologic parameters such as natural killer (NK) activity, the absolute number of T gamma lymphocytes, the percentages of beta- and gamma-globulin, and the amounts of IgA, IgG, IgM, and beta 2 microglobulin. To define further the nature of this IFN, both sera of the patients and normal donors of 50-to-79-year age group were characterized by a neutralization assay with an antiserum to HuIFN-alpha and HUIFN-beta. The IFN activity left when the testing sera were neutralization with these antisera was expressed as gamma-like IFN. The titers of gamma-like IFN in the sera of patients (n = 24, P less than 0.0001) showed a highly significant increase as compared with the normal controls (n = 20). When the correlation between prognosis of the disease and titers of serum IFN were investigated by measuring gamma-like IFN and acid-stable IFN in the sera of patients, all of nine patients with good prognosis after the cancer treatment showed significant decreased levels of gamma-like IFN (P less than 0.01) and acid-stable IFN (P less than 0.05) as compared with those on the time before cancer therapy. On the other hand, titers of gamma-like IFN in the sera of six patients with recurrent disease showed a significant increase as compared with those on the IFN measurement before cancer therapy (P less than 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)

Specific adoptive immunotherapy of malignant glioma with long-term cytotoxic T lymphocyte line expanded in T-cell growth factor. Experimental study and future prospects

The purposes of the current study were: (1) to investigate the immunoregulatory effects of T-cell growth factor (TCGF) on the activation and differentiation of syngeneic cytotoxic T lymphocyte (CTL) populations generated against a 20-methylcholanthrene-induced ependymoblastoma, 203-glioma, in C57BL/6 mice; and (2) to determine whether the glioma-specific CTL clone (G-CTLL) could be established by TCGF, and whether the in vivo efficacy of the cloned cells could be rendered more effective in adoptive therapy. It was found that TCGF largely allows the CTL populations to proliferate and thus can activate the depressed cytotoxic activity in tumour-bearing mice. Two lines of G-CTLL were successfully obtained by the limiting dilution technique. The G-CTLL retained a TCGF-dependent proliferative growth and a marked cytotoxic activity with target specificity for over 18 months, characterized by a surface phenotype of Lyt-1-.2.3+, Lyt-2 antibody blocking of cytotoxicity and the production of immune interferon in response to mitogen and tumour antigen. In the Winn assay and the adoptive transfer assay, the therapeutic effects were detected in intracranially inoculated tumours in mice. The in vivo efficacy was dependent on the dose of G-CTLL and on the time of the intravenous administration, although the transfer was inversely ineffective in conditions of increased intracranial pressure. The mechanism responsible for the in vivo effect was probably due to the adoptive immunity and/or the tumour-specific interferon production of G-CTLL.

Inhibition of cell division and antibody secretion by murine alpha/beta interferon: effects on plasmacytoma and hybridoma lymphoid cells

Murine alpha/beta interferon (IFN) inhibited the growth of myeloma cells in vitro. Independently of the cell growth inhibition, IFN also reduced the number of antibody secreting myeloma cells as measured by haemolytic plaque assay. The sensitivity of both MOPC 315 plasmacytoma cells and 4F4 hybridoma cells varied, though not to the same extent, depending on the dose of IFN used and the duration of exposure. Inhibition of PFC activity was observed after one day of IFN treatment while inhibition of cell growth was not detected until Day 2 of incubation. A dose of 20 u/ml IFN had no effect on the growth rate of MOPC 315 cells but with 100 u/ml the inhibition of growth was virtually complete. In contrast, an inhibition of PFC activity was observed at all the concentrations tested. The cell growth and PFC activity of 4F4 hybridoma cells, on the other hand, were both inhibited by IFN when used at concentrations as low as 1.25 u/ml. Incubation with higher concentrations of IFN resulted in a progressive reduction in cell growth and PFC activity of 4F4 cells, however to a lesser degree of inhibition compared to that observed with MOPC 315 cells. For example, although virtually 70% of MOPC 315 PFC could be inhibited by culture for two days in the presence of 100 u/ml, it was necessary to use 1,250 u/ml IFN for 4 days incubation before the similar level of PFC inhibition was achieved with 4F4 cells. IFN treatment resulted in an increase in both cellular volume and protein content and this effect was prevented when IFN was previously neutralised by a specific antiserum. IFN-treated cells also showed an inhibition in the incorporation of 3[H]-thymidine but no alteration in the rate of utilization of 35[S]-methionine, when compared with an equal number of control cells.

Improved culture conditions for quantitative evaluation of interleukin 2 production by frozen human lymphocytes

Several culture parameters were studied in order to establish methods for optimal and reproducible production of interleukin 2 (IL2) by thawed lymphocytes. Standard conditions, considered optimal for production by freshly separated lymphocytes (culture medium RPMI 1640 + 1% normal human serum + 10 micrograms/ml PHA), gave low and poorly reproducible results. An increased concentration of human serum (10 and 20%) in the medium improved production but best results were obtained by adding polyethylene glycol (PEG 6000, 0.1 mg/ml) to the culture medium. Furthermore, with the addition of PEG 6000, results became highly reproducible, thus permitting valid comparison of in vitro IL2 production by lymphocytes from normal donors and patients.

The interferons

An overview of the interferons is presented. A description of something of what is known about them is given, including: their genes; their protein structures and characteristics; their mechanisms of actions; and their varied biological effects emphasising particularly their immunomodulatory actions. Finally, a brief summary is made of the current status of human clinical studies that have been conducted with interferons in the oncological and viral fields, mentioning also recent findings in patients who have the acquired immunodeficiency syndrome (AIDS).

Human alpha-interferon enhances in vitro IgM rheumatoid factor synthesis by lymphocytes from normal subjects and rheumatoid arthritis patients

Alpha-interferon (alpha-IFN) was added to pokeweed mitogen (PWM) or Epstein-Barr virus stimulated human peripheral blood mononuclear cell cultures from normal subjects or patients with rheumatoid arthritis (RA). Alpha-IFN enhanced in vitro production of PWM induced IgG and IgM, and significantly enhanced PWM induced IgM rheumatoid factor (IgM-RF) production by lymphocytes both from normal subjects and RA patients. Enhancement was recorded whether cells were preincubated with alpha-IFN for 16 hours or with alpha-IFN present throughout the culture period. Alpha-IFN did not enhance IgM-RF production in the absence of PWM or T cells. Enhancement of IgM-RF production was not seen in Epstein-Barr virus stimulated cultures.

Differential cytostatic effect of interferon on murine BALB/c B- and T-cell tumors

The cytostatic effect of murine interferon (IFN) on several BALB/c-derived B- and T-cell tumor cells was examined. After incubation for 1 h in vitro with 1000 U of IFN, followed by intraperitoneal inoculation, tumor formation was not decreased in the case of B cell tumors or Lyt-1+2- or Lyt-1+2+3+ T cells tumors. Under the same conditions, the onset of tumor formation for Lyt-2+3+ T-cell tumors was delayed and the final incidence decreased. When the effect of IFN on cell multiplication in vitro was examined, Lyt-2+3+ T-tumor cells were found to be more sensitive to the cytostatic effect of IFN than Lyt-1+2+3+ T-tumor cells. This shows that the sensitivity of lymphocyte-derived tumor cells to the cytostatic effect of IFN is influenced by the type of differentiation of the cells.