Interferon enhances the amount of membrane-bound beta2-microglobulin and its release from human Burkitt cells

The beta2-microglobulin mRNA in human Daudi cells has a mutated initiation codon but is still inducible by interferon

The human Burkitt lymphoma cell line Daudi does not synthesize beta2-microglobulin (beta2m) and lacks the cell surface histocompatibility antigens. The cells, however, contain RNA hybridizing to a cloned human beta2m cDNA probe. cDNA from this Daudi beta2m RNA, was cloned and sequenced. By comparison with cDNA prepared from Ramos cells, which synthesized microglobulin, we determined the sequence of the 20 amino acid long leader peptide of pre-beta2m and show that in Daudi cells the initiator ATG has been mutated to ATC. Although Daudi beta2m RNA cannot be translated, interferon induces the beta2m RNA in Daudi cells as well as in normal human cells.

Dialysis-associated amyloidosis

Dialysis-related arthropathy represents a major complication of uremic patients treated by hemodialysis or other renal replacement therapies. Nearly 10 years ago, this syndrome was shown to be associated with a new type of amyloid, mainly composed of beta-2 microglobulin (beta 2-M). Retention of the beta 2-M protein due to chronic renal failure, although unquestionably a prerequisite for the occurrence of beta 2-M amyloidosis, appears not to be the unique pathogenetic factor involved in this complication. A role has also been attributed to an enhanced local or systemic generation of inflammatory mediators, an increased production of beta 2-M, and an altered metabolism of the molecule including partial proteolysis and glycation. It is possible that factors related to renal replacement therapy such as dialysis membrane biocompatibility also play a role. However, the clarification of the precise underlying mechanism(s) awaits further study. Because dialysis technology has progressed considerably during the last decade, a significant beta 2-M removal can be achieved at present using high-flux dialyzers. Moreover, a marked reduction in bioincompatibility during the dialysis procedure as manifested by activation of complement and stimulation of mononuclear blood cells can now be attained. Future studies will tell whether technical progress in dialysis technique results in a decrease in the incidence of symptomatic dialysis-associated amyloidosis.

Basic fibroblast growth factor induces 3T3 fibroblasts to synthesize and secrete a cyclophilin-like protein and beta 2-microglobulin

When stimulated by fibroblast growth factor (FGF) BALB/c 3T3 cells synthesize and secrete elevated amounts of five proteins called the 'superinducible proteins', or SIPs. The expression of these proteins is greatly enhanced if the cells are treated with cycloheximide during induction. The 24 kDa protein (SIP24) has been purified and antiserum raised against it. This protein is N-glycosylated and probably structurally constrained by one or more intramolecular disulfide bonds. The amino acid sequences of three of four peptides show significant identity with cyclophilin, an abundant cytoplasmic protein believed to mediate the immunosuppressive effects of cyclosporin A. Several members of the cyclophilin family have been identified, and cDNA clones of two cyclophilin-like proteins with signal sequences have been reported. Here we show that at least one cyclophilin-like protein is secreted and that its expression is regulated by growth factors. The 12.5 kDa protein (SIP12.5) was found to be immunoprecipitated by an antiserum raised to human beta 2-microglobulin. This protein is strongly induced by interferon, which is a characteristic of the beta 2-microglobulin gene. Thus, FGF stimulates mouse embryo 3T3 cells to produce two proteins related to immune regulatory molecules. This may reflect an interaction between immune cells and nonimmune cells that occurs in vivo during processes such as wound healing when growth factors are released locally.

Recombinant gamma interferon provokes resistance of human breast cancer cells to spontaneous and IL-2 activated non-MHC restricted cytotoxicity

Natural and lymphokine activated killer cells (NK and LAK) are believed to play an important role in the control of tumour progression and metastasis. Their specific receptors on tumours cells are still unknown. Several studies suggest that these cells recognise and eliminate abnormal cells with deleted or reduced expression of MHC class I molecules. Previous reports suggest that interferons (IFN), by increasing MHC class I expression on target cells, induce resistance to killing by NK cells. We investigated the role of MHC molecule expression by two human breast cancer cell lines T47D and ZR75-1 in their susceptibility to NK and LAK cells. These two cell lines spontaneously express low levels of HLA class I antigens but no HLA class II molecules. After IFN-gamma treatment they both overexpressed MHC class I and de novo expressed class II molecules as detected by flow cytometry, quantified by a radioimmunoassay and analysed by two-dimensional gel electrophoresis. Opposed to untreated cells these IFN-gamma treated cells were resistant to NK and LAK lysis. Furthermore, preincubation of IFN-gamma treated breast cancer cells with F(ab')2 fragments of monoclonal antibodies to HLA class I and HLA class II molecules was unable to restore lysis. In contrast, several complete monoclonal antibodies including anti-HLA class I and HLA class II induced the lysis of target cells whether or not they had been treated by IFN-gamma. The therapeutic use of monoclonal antibodies directed against antigens expressed on tumour cells (ADCC) in conjunction with interferon therapy should be discussed in lymphokine-based strategies for treatment of cancer patients.

IFN-induced modulation of histocompatibility antigens on human cells. Background, mechanisms and perspectives

IFN proteins are a family of lymphokines with anti-viral effects. Several other effects of IFNs have also been described, including enhancement of natural killer (NK) cell activity, enhancement of cytotoxic T-lymphocyte activity, and enhancement of the expression of major histocompatibility complex (MHC) antigens. The latter effects have been characterized as immunomodulatory, whereas the well-known inhibition of growth of malignant cells has been termed anti-proliferative. This review summarizes the current knowledge of the enhancement of MHC products by IFNs. Whereas the basic methodologies for demonstrating the enhancement are simple and reliable, especially when using flow cytometry (FCM), the biological relevance of this reaction is largely unknown. Based on recent findings, however, we have hypothesized that the above-mentioned diverse effects of IFNs are all - in some way or other - related to the classical anti-viral mechanism. This concept proposes that the MHC-enhancing effect of IFNs is a vital part of the immunological defense against virus infections and an integral part of the anti-viral effects of IFN proteins.

Differential expression and interferon response of HLA class I genes in thymocyte lines and response variants

cDNA clones which seem to represent the alleles of HLA-A and -B expressed by the thymoma MOLT-4 have been isolated and used as locus-specific probes to measure the corresponding mRNA levels in MOLT-4 and other human thymocyte lines, and the effect of interferon (IFN)-alpha and -gamma on these levels. It is shown in MOLT-4, and in its derived line YHHH, that HLA-B mRNA levels are undetectable before treatment but respond to IFN-alpha and -gamma more markedly than those of HLA-A. This differential induction is best shown with YHHH, which is hypersensitive to IFN-alpha, where the HLA-B mRNA levels increase to a level threefold those of HLA-A. Other thymocyte lines tested also showed preferential induction by IFN-alpha of HLA-B, although the basal levels of HLA-A and -B tended to be similar. The effect of the altered ratio of HLA-A to -B mRNA on surface expression of the antigens and the correlation between basal level expression and inducibility are discussed.

Quantitative modifications of major histocompatibility complex (MHC) antigens induced by recombinant gamma interferon in two human breast cancer lines

H466-B and T47-D breast carcinoma cell lines were treated with recombinant gamma interferon (r gamma IFN) to study major histocompatibility complex (MHC) class I and class II antigen responses. Untreated H466-B cells released B2 microglobulin (B2M) into the culture medium and expressed B2M and class I heavy chain on 100% of the cells. The expression of class II antigens (DR) was limited to 8 +/- 4% of the cells. This subpopulation was isolated by cell sorting and labelled with 35S methionine. Protein extracts were immunoprecipitated with anti-DR antibody and subjected to two dimensional non-equilibrium pH gradient electrophoresis (2D-PAGE). A normal pattern of expression of invariant, alpha and beta chains was shown. The MHC antigenic expression of H466-B parental cell line was not modified by interferon treatment. Untreated T47-D cells did not release B2M into the culture medium, expressed B2M and class I heavy chain on 100% of the cells but did not express class II molecules using radio-immunoassay or 2D-PAGE. As early as 24 h after r gamma IFN addition, T47-D cells released B2M into the medium, B2M and class I heavy chain were significantly greater than that of untreated cells, and class II antigenic expression was found, all these in a dose dependent manner. 2D-PAGE analysis of class II antigens revealed the profile of human DR molecules but this expression seemed incomplete since only single alpha and beta spots were detected suggesting a possible defect in the sialilation of DR molecules. These results show a heterogeneity in MHC antigenic responses to r gamma IFN and suggest that synthetized class II molecules may be incompletely processed.

The antitumor effects of interferon

Interferons show antitumor activity in patients with various malignancies. The mechanism(s) of the antitumor effects are not altogether clear. In one experimental animal model discussed herein, mice were injected with Friend erythroleukemia cells and treated with mouse interferon alpha/beta. The results suggest that interferon does not act directly on the tumor cells but acts via host mechanisms that are still ill defined.

Regulation of natural killer cytotoxicity by Escherichia coli-derived human interferon gamma

The abilities of Escherichia coli-derived human interferon gamma (IFN-gamma) and E. coli-derived human interferon-alpha A (IFN-alpha A) or -alpha 2 (IFN-alpha 2) to augment natural killer (NK) cytotoxicity were compared. When low concentrations (less than 10 antiviral units/ml) of interferons were used, and equal numbers of antiviral units of E. coli-derived IFN-gamma and E. coli-derived IFN-alpha A or IFN-alpha 2 were compared for their ability to augment NK, E. coli-derived IFN-gamma was found to be more active in augmenting NK against the K562 targets, than E. coli-derived IFN-alpha A or IFN-alpha 2. Antiviral units in these experiments were determined by the standard cytopathic effect assay using vesicular stomatitis virus (VSV)-challenged human fibroblasts, trisomic for chromosome 21. However, when these interferons were compared on a weight basis (ng/ml) or on a molar basis, their ability to augment NK against the K562 targets was comparable. These differences in the relative abilities of these interferons (when their concentrations were expressed in antiviral units/ml) to augment NK, were due to an approximately 100-fold difference in their specific activities (antiviral units per mg of interferon). These were 1.8 X 10(6) units/mg for E. coli-derived IFN-gamma, 2.0 X 10(8) units/mg for E. coli-derived IFN-alpha A, and 1.8 X 10(8) units/mg for E. coli-derived IFN-alpha 2. At concentrations higher than 10 units/ml, all these interferons showed a similar ability to augment NK. Studies on the kinetics of the augmentation revealed that in vitro treatment with E. coli-derived IFN-gamma for several hours was necessary for augmentation of NK against targets from haemopoietic human tumour cell lines (K562, Daudi). In contrast, alpha interferons were able to augment NK after treatment in vitro for significantly shorter periods (30 min or less with certain donors). Augmentation of NK cytotoxicity of human peripheral blood mononuclear leucocytes by E. coli-derived IFN-gamma was not accompanied by the induction of interleukin 2 (IL-2) production, suggesting that IL-2 is not involved in the augmentation of NK by IFN-gamma. A monoclonal antibody specific for human IFN-gamma blocked augmentation of NK by E. coli-derived IFN-gamma and natural IFN-gamma, but not by E. coli-derived IFN-alpha A or staphylococcal enterotoxin A (SEA).(ABSTRACT TRUNCATED AT 400 WORDS)

Receptor mediated pathways for interferon action: in vivo implications

High affinity receptors for human interferon (IFN) are a common surface component of human nucleated cells. A model culture system has been used to mark the activation of surface receptors by IFN as the first step in several, possibly separate, pathways of action, some of which depend on the continued presence of IFN. Two types of equilibrium binding can be seen: an initial one of short duration corresponding to receptor activation and a second of longer duration corresponding to activation of a second site by IFN. Various different responses to IFN are seen to be determined by one or other of these equilibria. In vivo, implications are discussed in terms of the pharmacokinetic distribution of IFN, with particular reference to intravenous injection. Desensitization of target cells with respect to late equilibrium effects is seen as a possible consequence of receptor activation against the background of changing IFN concentration in vivo. A modulating effect of combined IFN species is proposed.

Tumor growth stimulation in vitro by interferons

Interferons (IFNs) are a family of polypeptides originally identified as antiviral substances. Subsequently, other properties of interferons were recognized, including inhibition of cell proliferation, and effects on the immune response and on expression of surface antigens. In this paper we present evidence that interferons, even the highly purified cloned IFNs, can stimulate clonogenic tumor growth in vitro. Of 225 human tumor (HT) samples tested with IFN in a clonogenic assay (HTCA), 30 (13.3%) showed growth stimulation (greater than 2 S.E. above control). The phenomenon was observed most frequently with acute myeloid leukemia (6/22 samples, 27.3%), and renal (2/10, 20%) and breast cancer (4/21, 19%), but significantly less frequent in melanomas (2/34, 5.9%). As an independent assessment of proliferation, tritiated thymidine uptake by tumor cells was measured autoradiographically in 21 patients with multiple myeloma. A significant increase of the thymidine labeling index was seen in 4 (19%) of the samples. Since this growth stimulatory effect was also observed with cell lines which lack any contaminating immunoreactive cells, there is strong evidence that interferons can directly stimulate the proliferation of clonogenic tumor cells in vitro. Growth stimulation by interferons occurred preferentially with lower dosages. It is important to be cognizant of potential clinical implications of tumor growth stimulation by interferons.

Cellular RNA is not degraded in interferon-treated HeLa cells after poliovirus infection

A drastic inhibition of protein synthesis occurs in HeLa cells treated with human lymphoblastoid interferon and infected with poliovirus. At the time when this inhibition has been established no degradation of 32P-labelled ribosomal RNA can be detected. Isolation of the mRNAs from poliovirus-infected cells plus or minus interferon treatment, followed by translation in a reticulocyte lysate indicates that cellular mRNAs remain active. These results suggest that gross degradation of cellular RNA does not occur in interferon-treated poliovirus-infected HeLa cells and that a non-specific nuclease induced by 2'-5' A is not responsible for the inhibition of protein synthesis observed.

Quantification by flow cytofluorimetry of HLA class I molecules at the surface of murine cells transformed by cloned HLA genes

A method allowing quantitative analysis of the expression of foreign antigens at the surface of transformed cells is described. Aminoethyl-Sephadex G-25 beads labelled with different amounts of fluorescein isothiocyanate (FITC) were used to calibrate an Epics V cell sorter. The quantity of FITC molecules bound per bead was found to be a linear function of relative fluorescence intensity expressed by channel number for intermediate and high levels of fluorescence and a non-linear function for low levels. The lowest limit of detectable fluorescence was 3400 FITC molecules bound per bead. Using FITC-conjugated monoclonal antibodies (m.Ab.) the number of HLA class I molecules expressed at the surface of murine LMTK- (H-2Kk) cells transfected by cloned HLA class I genes was estimated and compared with the amount expressed on human B (Raji) and T (MOLT 4) lymphoblastoid reference cells. Murine transformed cells expressed approximately 3 times less HLA class I determinants per surface unit (micrometer 2) than Raji cells and 1.4 times less than MOLT 4 cells. Similar results were obtained by Scatchard analysis of the same populations using radiolabelled m.Ab. A detailed analysis of fluorescent cells showed that 5-20% of transformed cells expressed less than 33,000 HLA class I molecules/cell whereas most MOLT 4 cells exhibited at least 280,000 molecules/cell and the majority of Raji cells more than 700,000 molecules/cell. The expression of foreign antigen did not reduce the amount of H-2Kk molecules at the surface of transformed cells (mean of 350,000 molecules/cell).

Isolated interferon alpha-receptor complexes stabilized in vitro

We describe the extraction and stabilization in vitro of discrete complexes of interferon and cellular receptor proteins. A homogeneous complex of Mr 230 000 was extracted at the time of peak receptor binding (30 min). Complex formation was specific for human interferon. At later times a second complex could also be extracted suggesting transfer of interferon to a second site.

Cytofluorometric analysis of major histocompatibility antigens on human monocytes using monoclonal antibodies

The expression of HLA-A, B, C, and DR antigens was investigated on monocyte preparations by flow cytometry using various monoclonal antibodies. Essentially all human monocytes, either freshly isolated or after culture for several days, were stained for HLA-A, B, C, and DR antigens. When monocytes were incubated with Con-A-stimulated lymphocyte supernatants, an increase in HLA-A, B, C, and DR staining was observed. No increase was noted when two other monoclonal antibodies against non-HLA-related monocyte antigens (63D3 and 61D3) were studied under the same culture conditions. These results indicate that soluble factor(s) present in Con-A-stimulated lymphocyte supernatants modulate the expression of the major histocompatibility antigens on the surface of human monocytes.

Synergistic activities of type I (alpha, beta) and type II (gamma) murine interferons

Type I (alpha, beta) and type II (gamma) murine interferons are able to potentiate each other with respect to the inhibition of encephalomyocarditis (EMC) virus and of herpes simplex virus type 1 (HSV-1) multiplication in a murine cell line (DBT). Examination of two double-stranded RNA-dependent enzymes in DBT cells, the 2-5A synthetase and the 67,000 MW protein phosphokinase indicates that mixed interferon preparations act synergistically at least with respect to an increase in the activity of the former enzyme. The results obtained with gamma interferons of different origin and of different specific activity suggest that interferon itself, rather than the lymphokines present in the interferon preparations, is responsible for the synergistic effect.

Interferon increases HLA synthesis in melanoma cells: interferon-resistant and -sensitive cell lines

We report that human leukocyte interferon preparations increase the expression of beta 2-microglobulin by 100-200% on the surface of normal fibroblast and melanoma cell lines sensitive to interferon. This increase in expression can be correlated with an increase in HLA synthesis as measured by incorporation of [35S]methionine in these antigens. This enhanced HLA synthesis, which is 5- to 17-fold, is time dependent and dose related. Synchronized cells in the G0/G1 phase of the cell cycle appear to be more sensitive to this interferon action. Neither an increase in surface expression nor in HLA synthesis is observed in a melanoma cell line resistant to the antiviral and antigrowth effects of interferon. Furthermore, there appears to be a stronger correlation between this increased HLA synthesis and the antiviral function than between it and the antiproliferative action of interferon.

Control of HLA-A,B,C synthesis and expression in interferon-treated cells

Cytofluorimetric analyses with monoclonal antibodies were used to follow the specific effect of highly purified human leucocyte interferon (IFN-alpha) on the expression of transplantation antigens (HLA)1 in Molt 4, a thymus leukaemia cell line. After a lag period of approximately 10 h the amount of HLA steadily increases to reach a maximum at day six of approximately 10 times its original. The effect is reversible and due to an increase in the rate of synthesis of HLA and beta 2m molecules as demonstrated by analysis of [35S]methionine incorporation into specific proteins after a 3-h pulse of Molt 4 cells treated with IFN-alpha for one or six days. A dramatic increase in the amount of mRNA that hybridised with a [32P]cDNA probe containing HLA sequences has also been demonstrated. Surface iodination of IFN-treated Molt 4 cells showed an increase in the iodinated HLA and beta 2m chains and in addition another, apparently unrelated, component with an apparent mol. wt. of 16 000. This component, which appears after incubations with IFN-alpha for longer than 1 h at 37 degrees C, was also detected in the B lymphoid cell lines RAJI and DAUDI.