Mechanism of induction of class I major histocompatibility antigen expression by murine leukemia virus

Alterations in expression of major histocompatibility complex (MHC) antigens on tumor cells clearly correlate with the tumorgenicity and metastatic potential of those cells. These changes in the biological behavior of the tumor cells are presumably secondary to resulting changes in their susceptibility to immune recognition and destruction. Murine leukemia viruses (MuLV) exert regulatory effects on class I genes of the MHC locus. MuLV infection results in substantial increases in cell surface expression of all three class I MHC antigens. These viral effects on MHC antigen expression profoundly influence immune-mediated interaction with the infected cells, as assessed by cytotoxic T lymphocyte recognition and killing. Control of class I MHC and beta-2 microglobulin genes by MuLV takes place via a trans-acting molecular mechanism. MuLV controls expression of widely separated endogenous cellular MHC genes, transfected xenogeneic class I MHC genes, and unintegrated chimeric genes consisting of fragments of class I MHC genes linked to a bacterial reporter gene. These findings indicate that MuLV exerts its effects on MHC expression via a trans mechanism. The MuLV-responsive sequences on the MHC genes appear to lie within 1.2 kilobases upstream of the initiation codon for those genes.     

Direct induction of Ia antigen on murine thyroid-derived epithelial cells by reovirus

The ability of thyroid follicular epithelial cells (TFEC) to act as APC is linked to the expression of class II (Ia) molecules of the MHC. The cloned murine thyroid-derived epithelial cell line M.5 was used to demonstrate the potential effects of virus in the direct induction of Ia molecules on TFEC. Membrane binding and replication of reovirus type 1 in TFEC was demonstrated using fluorescein-labeled antireovirus antibody and fluorescence microscopy. One consequence of the interaction between reovirus and M.5 cells was the induction of Ia Ag and augmented class I molecule expression in M.5 cells. The levels of Ia expression at three days after reovirus binding were amplified 17.3-fold over controls and were 2-fold less than that seen upon treatment of M.5 cells with IFN-gamma. Supernatant transfer experiments showed that the induction of Ia expression was directly linked to the binding of virus to M.5 cells, and was not dependent upon virus replication or the presence of IFN. These results indicate that early events of reovirus binding or receptor internalization on TFEC initiate a signaling process which results in the induction of class II and augmentation of class I MHC protein levels on the cell surface.     

Immunosuppressive properties of murine trophoblast

The modification of the immunological response by murine trophoblast cells of different sources was investigated using the mixed lymphocyte reaction (MLR) and the cell mediated lympholysis (CML) test. MLR between C57BL (H-2b) stimulator splenocytes (mitomycin C treated in the unidirectional MLR) and BALB/c (H-2d) responder lymph node cells were markedly suppressed by trophoblast of ectoplacental cone (EPC) and placental origin. The same in vitro effect was observed with supernatants (SN) of trophoblast cells and with supernatants of blastocysts. Addition of anti-progesterone serum (APS), anti-testosterone serum (RAT), and anti-immunoglobulin serum (RAHIg) in serial dilutions to the trophoblast-MLR system revealed that the immunosuppressive effect of trophoblast giant cells and trophoblast giant cell culture supernatants can be abolished with APS. Identical results were obtained with APS added to immunosuppressive doses of progesterone. CML between C57BL responder lymph node cells and mitomycin C-treated BALB/c stimulator spleen cells was also markedly suppressed when trophoblast of EPC origin was added. A similar suppression of cytotoxic T-cell induction was seen when progesterone was added to the system. The immunosuppressive action of trophoblast as detected in vitro is likely to play an important role in the maintainance of pregnancy by protecting the semiallogeneic conceptus against immune aggression by the maternal immune system.     

Rapid induction of Fas antigen mRNA expression in vivo by cycloheximide

The effect of administration into rats of cycloheximide on the expression of genes, such as tissue transglutaminase, testosterone-repressed prostate message-2, Fas antigen, bcl-2, DNase I, and poly(ADP-ribose) polymerase, which were believed to be involved in the mechanism of apoptosis, was studied. While the effect of cycloheximide on the expression of genes other than Fas antigen was modest, only the expression of Fas antigen was elevated rapidly in most of the organs examined. A possible direct effect of cycloheximide on cells per se to induce Fas antigen mRNA expression was demonstrated by the tissue culture study using L929 fibroblast cells, although the magnitude of the induction detected in vitro was small compared with that in vivo. This induction of Fas antigen mRNA by cycloheximide is a first report on the modulation of Fas antigen mRNA expression in vivo. © 1997 John Wiley & Sons, Ltd.     

Differential induction of H-2K vs H-2D class I major histocompatibility complex antigen expression by murine recombinant interferon-gamma

The results presented here indicate that recombinant murine interferon-gamma can cause a dramatic differential induction of two distinct class I MHC molecules. Thus, IFN-gamma treatment of the murine leukemia virus (MuLV)-induced AKR SL3 tumor, a cell line that normally expresses moderate levels of class I MHC antigens, resulted in a large increase in H-2Dk expression, but no change or a slight decrease in H-2Kk expression as measured by cytofluorography. Explanations of the selective enhancement of Dk expression based on increased Fc receptor display or differential kinetics of induction were ruled out. The phenomenon was observed over a wide range of doses of IFN-gamma and with two different monoclonal antibodies to Kk, the latter finding making it unlikely that an altered form of the Kk molecule was induced. The same differential induction of the Dk antigen was observed for the LBRM.5A4 tumor cell line. Because LBRM.5A4 is also MuLV+ but of congenic B10.BR (H-2k) origin, these results were consistent with the possibility that such differential induction was associated with the H-2k haplotype and/or MuLV. The implications of these results, as a possible mechanism of tumor cell escape from an immune surveillance system monitored by class I MHC-restricted T cells and as a useful model system to dissect the mechanism of IFN-gamma induction of class I MHC antigens, are discussed.     

Trypsin inhibitors inhibit induction by interferon-gamma of HLA-DR antigen expression on human skin cells

Serine protease inhibitors with a specificity for trypsin inhibit interferon-gamma (INF-gamma)-induced HLA-DR expression on a hybrid human epidermal cell line (H12), dermal fibroblasts, and primary keratinocytes. Protease inhibitors with a specificity for chymotrypsin or papain fail to inhibit IFN-gamma. The inhibitory effect of the trypsin inhibitors is similar to that of glucocorticoids in that it is a transient event, fading with length of exposure to IFN-gamma, and is reversed by the addition of dibutyryl cyclic AMP (dbcAMP) and phospholipase C(PLC) from Clostridium perfringens. In H12 cells, dbcAMP and PLC enhance the IFN-gamma induction of HLA-DR, but do not induce in the absence of INF-gamma. Evidence suggests that the protease inhibitors, as well as dbcAMP and PLC, may modulate HLA-DR expression at a post-translational site as well as during IFN-gamma signal transduction. These results suggest that trypsin-like protease activity may be required for cellular HLA-DR antigen expression following exposure to IFN-gamma.     

Expression of MHC antigens on murine trophoblast and their modulation by interferon

Primary cultures of defined populations of mouse trophoblast, isolated from mature placentas, were analyzed for their MHC antigen expression and for the modulatory effect of interferon (IFN) by antibody- and complement-mediated cytotoxicity and flow cytofluorometry. The cells were obtained from placentas by enzymatic digestion, followed by Percoll gradient fractionation, and are large, fetally derived epithelial cells, which we previously characterized and identified as trophoblast cells. After 2 days in culture, a significant proportion of the trophoblast cells were susceptible to antibody- and complement-mediated lysis by anti-paternal strain alloantisera (40%) and, to a lesser degree, by an anti-class I monoclonal antibody (20%). Flow cytofluorometric analysis indicated that 20 to 50% of the cultured trophoblast cells expressed low levels of paternal strain class I antigens as compared to L cell fibroblasts. After culture for 48 hr with IFN-alpha/beta or IFN-gamma, the percent of class I-positive cells was increased to 68 to 76%, as was the mean fluorescence intensity, which correlated with the increased percent of antibody- and complement-mediated specific lysis (73%). No expression of class II MHC antigen by the cultured trophoblast cells was detected, even after culture in the presence of IFN-gamma. The cultured trophoblast cells, when tested for alkaline phosphatase (AP) activity, were composed of strongly positive and weakly positive subpopulations. An inverse correlation between strength of AP activity and the expression of H-2 was observed by double staining. These results indicate that trophoblast cells cultured in vitro are able to express paternal strain class I but not class II MHC antigens, as has been reported in vivo, and that this expression can be modulated by IFN. Further study of these cells should provide important clues for the understanding of materno-fetal coexistence in the face of MHC antigen differences.     

Hormonal induction of specific protein synthesis in murine Leydig tumor cells

The M5480A murine Leydig cell tumor was used to investigate the effects of three hormones, which produce distinct biochemical actions, on cytoplasmic protein synthesis. Human choriogonadotropin treatment of tumor-bearing mice induced the synthesis of six proteins with relative molecular weights (Mr) of 135K, 82K, 60K, 19K, 18.2K and 17.3K (K = kilodaltons). Diethylstilbestrol induced one protein peak in common with the gonadotropin Mr = 135K) and three additional proteins with Mr's of 120K, 50K and 36K. Epidermal growth factor induced one major protein with Mr = 33K, which is similar to that of a protein induced in murine epidermal cells by tumor promoters. These studies demonstrate the induction of specific gene products in a hormone-responsive tumor.     

Vascular endothelial growth factor receptor-3 mediates induction of corneal alloimmunity

There are no studies so far linking molecular regulation of lymphangiogenesis and induction of adaptive immunity. Here, we show that blockade of vascular endothelial growth factor receptor-3 (VEGFR-3) signaling significantly suppresses corneal antigen-presenting (dendritic) cell trafficking to draining lymph nodes, induction of delayed-type hypersensitivity and rejection of corneal transplants. Regulating the function of VEGFR-3 may therefore be a mechanism for modulating adaptive immunity in the periphery.     

Identical D region sequences expressed by murine monoclonal antibodies specific for a human tumor-associated antigen

Sequence analysis has revealed significant structural similarities among murine mAb specific for the human tumor-associated Ag GA733. Antibodies generated in independent immunizations, either with Ag-positive tumor cells or with anti-idiotypic antibodies produced by immunization of goats with a GA733-specific antibody, all use members of the same gene families; remarkably, they also express identical amino acid sequences in their H chain CDR3. Inasmuch as this region normally exhibits considerable sequence variability, the identity displayed by the antibodies indicates a requirement for this particular sequence in the generation of their specificity for the GA733 antigen. Moreover, this homology suggests that the antibodies recognize a common determinant on the Ag, and that the polyclonal anti-idiotypic antibodies can functionally mimic the Ag at the level of the structure of the Ag-specific antibody that is induced.     

The murine male antigen. I. Sensitive detection by the PEC transfer system

The peritoneal exudate cell (PEC) transfer system was investigated as a means of studying the murine male antigen (H-Y). The initial studies reported here established: (1) The sensitive detection by the PEC technique of male incompatibility; (2) the time interval and dose range which produces significant immunity to H-Y within the PEC system; (3) the specificity of the induction of immunity to H-Y; and (4) the specificity of the expression of anti-H-Y immunity. It is concluded that the PEC system provides a sensitive nonsubjective approach to the study of histo-compatibility barriers.     

Developmental expression of macronuclear specific antigen in Paramecium caudatum

We obtained a monoclonal antibody (MA-1) specific for macronuclei of the ciliate Paramecium caudotum and P. dubosqui. Immunoblotting showed that the antigen was a poly-peptide of 50 kilodalton (kDa). During the process of nuclear differentiation in P. caudatum, the MA-1 antigens appeared in the macronuclear anlagen immediately after four out of eight post zygotic nuclei differentiated morphologically into the macro-nuclear anlagen. Afterwards, the antigens could be detected in the macronucleus through the cell cycle, and disappeared when the macronucleus began to degenerate in exconjugant cells. These results suggest that the antigens may play a role in the differentiation and function of the macronucleus. © 1992 Wiley-Liss, Inc.     

Effect of biolinker on the detection of prostate specific antigen in an interferometry

Prostate-specific antigen (PSA) has been identified as a significant biomarker for prostate cancer screening. Heavily-doped porous silicon, etched to form a Fabry-Perot fringe pattern, can be applied to an interferometric sensing for detecting PSA bound with PSA-antibody. In the previous works, a calyx crown derivative (Prolinker-A) was used as an alternative biolinker on the porous silicon surface for interferometric biosensing of DNA-damaging chemical instead of employing the conventional biomolecular affinity method using biotin, which resulted in a denser linker formation. In this study, G5 amineterminated PAMAM (poly amidoamine) dendrimer as a biolinker, was applied to an interferometric sensing of PSA by using porous silicon, which shows the enhancement of adhesion capability and increase of functional groups more than those with Prolinker-A. Considerably low level down to 1 ng/mL of PSA could be detected by this sensing system.     

Membrane vesicles shed by murine melanoma cells selectively inhibit the expression of Ia antigen by macrophages

We previously demonstrated that membrane vesicles shed by the F10 variant of the murine B16 melanoma cell line inhibited the induction by interferon-gamma (IFN) of murine macrophage immune response region-associated (Ia) antigen expression. In this paper we present evidence that the inhibition of macrophage Ia antigen expression is a selective effect of vesicles and characterize its temporal requirements. Membrane vesicles shed from F10 cells did not affect the expression of macrophage H-2K or H-2D antigens under conditions shown to profoundly inhibit Ia antigen expression. Similarly, the induction of plasminogen activator and interleukin 1 from macrophages was not inhibited by the vesicles. The vesicles did not measurably decrease total cellular RNA or protein synthesis. Macrophages were sensitive to the inhibitory effects of the vesicles during the induction and maintenance phases of Ia expression. Pretreatment of macrophages with vesicles before culture with IFN did not reduce the induction of Ia. The rate of decline of Ia expression after removal of IFN was unaffected by the presence of vesicles. Removal of vesicles from cultures of IFN-treated macrophages resulted in only a partial recovery of Ia expression, suggesting that the inhibition of Ia expression may be a slowly reversible process. The selective and partially reversible inhibition of Ia expression by vesicles shed from the plasma membrane of tumor cells is a possible mechanism whereby tumor-bearing hosts may become immunocompromised.     

Intracrine induction of 11beta-hydroxysteroid dehydrogenase type 1 expression by glucocorticoid potentiates prostaglandin production in the human chorionic trophoblast

Glucocorticoids are involved in the modulation of the release of parturition hormones from the fetal membranes and placenta, where their actions are determined by the prereceptor glucocorticoid metabolizing enzyme 11beta-hydroxysteroid dehydrogenase (11beta-HSD). Two distinct isozymes of 11beta-HSD have been characterized. In the fetal membranes, 11beta-HSD1 is the predominate isozyme; it converts biologically inert 11-ketone glucocorticoid metabolites into active glucocorticoids. Sequence analysis of the cloned 11beta-HSD1 gene revealed a putative glucocorticoid response element in the promoter region. However, whether glucocorticoids modulate 11beta-HSD1 expression in the fetal membranes is unknown. In this study, 11beta-HSD1 and glucocorticoid receptor (GR) were coexpressed in the chorionic trophoblast. Radiometric conversion assay and Northern blot analysis revealed that both 11beta-HSD1 reductase activity and mRNA levels were increased by dexamethasone (1 microM, 0.1 microM) in the cultured chorionic trophoblast, and the effects were blocked by GR antagonist RU486 (1 microM). Prior induction of 11beta-HSD1 by dexamethasone potentiated the subsequent stimulation of prostaglandin H synthetase 2 expression and secretion of prostaglandin E(2) by cortisone in the chorionic trophoblast. There is colocalization of 11beta-HSD1 and GR in the chorionic trophoblast. By binding to GR, glucocorticoids induce the expression of 11beta-HSD1 by a possible intracrine mechanism, thereby amplifying the actions of glucocorticoids on prostaglandin production in the fetal membranes. This cascade of events initiated by glucocorticoids may play an important role in the positive feed-forward mechanisms of labor.