Increased Major Histocompatibility Complex Class Research Articles

A mouse cytomegalovirus glycoprotein, gp34, forms a complex with folded class I MHC molecules in the ER which is not retained but is transported to the cell surface.

Murine cytomegalovirus (MCMV) interferes with antigen presentation by means of retaining major histocompatibility complex (MHC) class I molecules in the endoplasmic reticulum (ER). Here we identify and characterize an MCMV-encoded glycoprotein, gp34, which tightly associates with properly conformed MHC class I molecules in the ER. Gp34 is synthesized in large quantities during MCMV infection and it leaves the ER only in association with MHC class I complexes. Many but not all class I molecules are retained in the ER during the early phase of MCMV infection, and we observe an inverse correlation between amounts of gp34 synthesized during the course of infection and class I retention. An MCMV deletion mutant lacking several genes, including the gene encoding gp34, shows increased class I retention. Thus, MCMV gp34 may counteract class I retention, perhaps to decrease susceptibility of infected cells to recognition by natural killer cells.

Immunoreactivity of the central nervous system in cats with a Borna disease-like meningoencephalomyelitis (staggering disease).

The inflammatory cell composition and the expression of major histocompatibility complex (MHC) antigens in the central nervous system (CNS) of 13 cats with a spontaneous, Borna disease-like meningoencephalomyelitis (staggering disease) was investigated by immunohistochemistry with a panel of monoclonal and polyclonal antibodies. T lymphocytes were the predominating inflammatory cells within the adventitial space. CD4+ T cells were more abundant than CD8+ T cells. Scattered IgG-, IgA- and IgM-containing cells were found in the adventitial space and surrounding neuropil, often adjacent to neurons. There was a markedly increased MHC class II expression in cells morphologically resembling microglia. In several cats, Borna disease virus specific antigen was detected, but only in a few cells, mainly of macrophage character. Our findings indicate a long-standing inflammatory reaction in the CNS of cats with staggering disease, possibly triggered and sustained by a persistent viral infection.

Immunoreactivity of the central nervous system in cats with a Borna disease-like meningoencephalomyelitis (staggering disease)

The inflammatory cell composition and the expression of major histocompatibility complex (MHC) antigens in the central nervous system (CNS) of 13 cats with a spontaneous, Borna disease-like meningoencephalomyelitis (staggering disease) was investigated by immunohistochemistry with a panel of monoclonal and polyclonal antibodies. T lymphocytes were the predominating inflammatory cells within the adventitial space. CD4+ T cells were more abundant than CD8+ T cells. Scattered IgG-, IgA- and IgM-containing cells were found in the adventitial space and surrounding neuropil, often adjacent to neurons. There was a markedly increased MHC class II expression in cells morphologically resembling microglia. In several cats, Borna disease virus specific antigen was detected, but only in a few cells, mainly of macrophage character. Our findings indicate a long-standing inflammatory reaction in the CNS of cats with staggering disease, possibly triggered and sustained by a persistent viral infection.

Presentation of exogenous antigens by macrophages: analysis of major histocompatibility complex class I and II presentation and regulation by cytokines

There is an antigen presenting cell (APC) in the lymphoid organs capable of presenting exogenous antigen (Ag) with major histocompatibility complex (MHC) class I molecules. This study was initiated to isolate clones of these APC to definitively establish their phenotype and to further study their properties. Murine bone marrow macrophages (BM M psi) were immortalized by overexpression myc and raf oncogenes. Five BM M psi cell lines were generated that are phagocytic and expressed at their surface M psi differentiation Ag. All five cell lines processed and presented exogenous ovalbumin (OVA) with MHC class I molecules. They all presented OVA-linked to a phagocytic substrate 10(2)-10(4)-fold more efficiently than soluble Ag. Clonal isolates of two of the M psi cell lines had an identical phenotype and functional properties as the uncloned lines. These results definitively establish that M psi are APC with the capacity of presenting exogenous Ag with MHC class I molecules. Interferon (IFN)-gamma interleukin-4, granulocyte-macrophage colony stimulating factor and lipopolysaccharide either alone or in combination induced little or no augmentation and in some cases decreased presentation of exogenous OVA with MHC class I. In contrast, all of M psi activating factors increased MHC class I expression. Moreover, IFN-gamma increased the presentation of cytosolic OVA, demonstrating differences between the presentation of cytosolic Ag versus exogenous Ag with MHC class I. Finally, some lines constitutively processed and presented exogenous OVA with MHC class II while others only presented after stimulation with IFN-gamma. These results demonstrate that the pathways involved in the presentation of exogenous Ag with MHC class I and class II are independently regulated and that a cloned cell is capable of presenting exogenous Ag through both pathways.

Interferon-gamma induces a cell surface phenotype switch on T84 intestinal epithelial cells.

Intestinal epithelia are in intimate contact with submucosal and intraepithelial lymphocytes. The concentration of intraepithelial lymphocytes increases during inflammatory processes, and, when stimulated, these cells generate cytokines such as interferon-gamma (IFN-gamma). In this study, we examined the effect of recombinant human IFN-gamma on ion transport events in T84 cells, a crypt epithelial cell line widely used to study electrogenic Cl- secretion, the transport event responsible for mucosal hydration. Epithelial exposure to IFN-gamma brought about a marked attenuation in stimulated Cl- secretion, as measured by generation of short-circuit current (ISC). This IFN-gamma-elicited decrease in the Cl- secretory response was present for a variety of specific agonists, appeared largely due to IFN-gamma interactions with the basolateral surface, and did not result from a defect in second messenger generation. Efflux and uptake studies were utilized to functionally define the individual cell surface transport proteins that participate in Cl- secretion and revealed that, in response to epithelial exposure to IFN-gamma, apical Cl- channels and basolateral Na(+)-K(+)-2Cl- cotransporters, K+ channels, and Na-K-adenosinetriphosphatase were all functionally downregulated. [3H]bumetanide binding assays suggested that surface expression of the cotransporter was diminished by > 70% after IFN-gamma preexposure. Concurrently, surface immunofluorescence studies revealed that epithelial exposure to IFN-gamma brought about the induction of major histocompatibility complex (MHC) class II molecule expression on T84 epithelial monolayers and markedly increased MHC class I surface expression. Finally, neutrophil-epithelial adhesion studies revealed that preexposure of epithelial monolayers to IFN-gamma elicited a beta 2-integrin-dependent induction of neutrophil adhesion.(ABSTRACT TRUNCATED AT 250 WORDS)

HLA class I heavy-chain gene promoter elements mediating synergy between tumor necrosis factor and interferons.

The cytokines tumor necrosis factor (TNF), beta interferon (IFN-beta), and IFN-gamma increase major histocompatibility complex class I molecule expression. A greater than additive (i.e., synergistic) induction of class I heavy-chain mRNA is observed in HeLa cells treated with TNF in combination with either type of IFN. To define the cis-acting elements mediating cytokine synergy, the promoter of a human major histocompatibility complex class I heavy-chain gene (HLA-B7) was placed in front of a reporter gene and transfected into HeLa cells. Deletion analysis mapped the elements required for synergy to a 40-bp region containing a kappa B-like element, which is necessary for the response to TNF, and an interferon consensus sequence (ICS), which is necessary for the responses to IFNs. When the orientation of these elements was reversed or their normal 20-bp spacing was reduced by 5 or 10 bp, i.e., one half or one full turn of the DNA helix, essentially equivalent responses were obtained, suggesting that these parameters are not critical. In electromobility shift assays, a p50-containing NF-kappa B nuclear factor from TNF-treated cells binds kappa B-containing probes, and ISGF-2 from IFN-gamma-treated cells binds ICS-containing probes. A probe containing both the kappa B and ICS elements (kappa B-ICS) forms a novel complex with nuclear factors isolated from cells treated with both TNF and IFN-gamma; this complex also forms when nuclear factors from individually cytokine-treated cells are mixed in vitro. The natural variant ICS found in HLA-A responds to IFN-gamma and can mediate synergy with TNF. However, the variant kappa B found in HLA-C does not respond to TNF, nor can it mediate synergy between TNF and IFN-gamma. These observations suggest that synergy between TNF and IFNs in the induction of HLA class I gene expression results from the sum of individual interactions of cytokine-activated enhancer-binding factors with the transcription initiation complex.

HLA Class I Heavy-Chain Gene Promoter Elements Mediating Synergy Between Tumor Necrosis Factor and Interferons

The cytokines tumor necrosis factor (TNF), beta interferon (IFN-beta), and IFN-gamma increase major histocompatibility complex class I molecule expression. A greater than additive (i.e., synergistic) induction of class I heavy-chain mRNA is observed in HeLa cells treated with TNF in combination with either type of IFN. To define the cis-acting elements mediating cytokine synergy, the promoter of a human major histocompatibility complex class I heavy-chain gene (HLA-B7) was placed in front of a reporter gene and transfected into HeLa cells. Deletion analysis mapped the elements required for synergy to a 40-bp region containing a kappa B-like element, which is necessary for the response to TNF, and an interferon consensus sequence (ICS), which is necessary for the responses to IFNs. When the orientation of these elements was reversed or their normal 20-bp spacing was reduced by 5 or 10 bp, i.e., one half or one full turn of the DNA helix, essentially equivalent responses were obtained, suggesting that these parameters are not critical. In electromobility shift assays, a p50-containing NF-kappa B nuclear factor from TNF-treated cells binds kappa B-containing probes, and ISGF-2 from IFN-gamma-treated cells binds ICS-containing probes. A probe containing both the kappa B and ICS elements (kappa B-ICS) forms a novel complex with nuclear factors isolated from cells treated with both TNF and IFN-gamma; this complex also forms when nuclear factors from individually cytokine-treated cells are mixed in vitro. The natural variant ICS found in HLA-A responds to IFN-gamma and can mediate synergy with TNF. However, the variant kappa B found in HLA-C does not respond to TNF, nor can it mediate synergy between TNF and IFN-gamma. These observations suggest that synergy between TNF and IFNs in the induction of HLA class I gene expression results from the sum of individual interactions of cytokine-activated enhancer-binding factors with the transcription initiation complex.

FOETO‐MATERNAL COMPATIBILITY IN HLA‐DR, ‐DQ, AND ‐DP LOCI IN FINNISH COUPLES SUFFERING FROM RECURRENT SPONTANEOUS ABORTIONS

The polymorphism of Major Histocompatibility Complex (MHC) class II genes DRB, DQA, DQB, and DPA was studied by TaqI Restriction Fragment Length Polymorphism (RFLP) in recurrent spontaneous abortions (RSA). The study group consisted of 35 primary abortion (PA) couples (no children) and 15 secondary abortion (SA) couples (1-2 children before abortions). We found no increase in DR-DQ compatibility between the mother and the foetus in the Finnish RSA group. In contrast to findings in some other populations, foeto-maternal incompatibility was increased in the PA group. Thus, our results do not support the theory that increased MHC class II compatibility is a cause of abortions as such. The Finns are a small and relatively isolated population with a unique gene inheritance. Thus, one can speculate that, if the human MHC class II is in the linkage with disadvantageous 'fertility genes', and these genes might nonetheless still be clustered in only a few MHC haplotypes among the Finns. This would be the reason, that DR-DQ sharing is not seen. The presence of rare HLA alleles, such as DR2 and DR6, among the aborters also supports this. In addition, this study extends our previous findings on MHC class III in regards to PA and SA couples differing immunogenetically from each other. In MHC class II, this was most obvious in the DPA1 locus. The vast majority of SA women were heterozygous for the two most common DPA1 alleles (14.0 kb and 13.5 kb), resulting in significantly smaller chances for a DPA1 mismatched foetus to occur in the SA group than in the controls or in the PA women.

Inflammatory cells in the peripheral nervous system in motor neuron disease.

We examined post-mortem material of the peripheral nervous system of 26 cases of motor neuron disease (MND) for the presence of lymphocyte subsets and macrophages. Findings were quantified and compared with those in control nerves. Lymphocytes in chronic and acute axonal degeneration were studied in sural nerve biopsy and animal material. Signs of demyelination were studied in MND and controls with infiltrates of T cells. A few T lymphocytes were scattered diffusely within the fascicles. The numbers did not differ between MND and controls. About half of the T cells was positive for CD45RA, the other half being positive for CD45RO. T cells were negative for CD25, CD54 and major histocompatibility complex (MHC)-class II. There were hardly any B lymphocytes. The numbers of lymphocytes in nerves with and without axonal degeneration did not differ. Increased MHC class II expression was present on denervated Schwann cells and macrophages in MND and in sural nerves with axonal degeneration. Macrophages were increased in number and in size, both in MND and in control material with axonal degeneration. No signs of demyelination were present either in MND or in controls. It is concluded that a T cell-mediated process in peripheral nerves in MND is very unlikely.

Dissection of human Langerhans cells' allostimulatory function: The need for an activation step for full development of accessory function

In the present study, we analyzed the mechanism by which human Langerhans cells (LC), the dendritic cells (DC) from epidermis, support the induction of a primary allogeneic T cell response. We reported that paraformaldehyde (PF) fixation completely abrogated the stimulatory property of freshly isolated LC, although the level of major histocompatibility complex (MHC) class II antigen (Ag) expression was unaltered by the fixative. Addition of either interleukin (IL)-1 beta and/or IL-6, during the mixed epidermal cell lymphocyte reaction, failed to restore the proliferative response. By contrast, when human LC were incubated for 3 days in culture medium before fixation, they retained a low but significant allostimulatory capacity. Trypsin treatment of incubated LC before fixation did not impair their function, suggesting that stimulatory activity by fixed incubated LC did not merely reflect a repair of LC membrane after trypsin trauma suffered during epidermal cell (EC) isolation. More interestingly, we found that addition of interferon-gamma during LC incubation mediated an enhanced allostimulatory activity by the PF-fixed LC. Acquisition of allostimulatory property by in vitro activated and fixed LC did not correlate with increased MHC class II Ag expression at the cell surface. By contrast, we showed that ICAM-1 Ag expression by human LC is involved in this maturation process. Finally, we found that once human LC have been activated, IL-1 beta, but not IL-6, could serve as a costimulatory factor in the primary allogeneic T cell response. In conclusion, the data suggest that human LC accessory function is not constitutive but requires an activation step which can be provided by interferon-gamma during LC-T cell interaction.

Expression of major histocompatibility complex (MHC) class I genes in astrocytes correlates with the presence of nuclear factors that bind to constitutive and inducible enahcers

The molecular basis of constitutive and inducible major histocompatibility complex (MHC) class I gene expression was studied in murine astrocytes in primary culture. Astrocytes constitutively expressed MHC class I molecules and treatment of these cells with interferon-γ (IFN-γ) further induced expression. The conserved region containing the upstream MHC class I regulatory element (MHC-CRE) and juxtaposed interferon consensus sequence (ICS) enhanced consttutive MHC class I promoter activity. As seen with cell surface expression of MHC molecules, treatment of astrocytes with IFN-γ increased MHC class I promoter activity. Inducible expression required the presence of the MHC-CRE/ICS enhancer region. Nuclear factors that bind to the MHC-CRE and ICS were constitutively expressed in cultured astrocytes and IFN-γ treatment further induced binding activity both to the MHC-CRE and ICS and correlated with induction of MHC class I gene expression. This study identifies the MHC-CRE and ICS as the major cis elements in controlling MHC class I promoter activity and suggests that the expression of nuclear factor binding activities to these enhancer elements is a basic transactivating mechanism for the expression of MHC class I genes in astrocytes.

Major histocompatibility complex class II antigen expression on leucocyte subpopulations in the draining lymph node and tumour in the early phase of bacillus-Calmette-Guérin-induced tumour regression.

We investigated the cellular composition and the major histocompatibility complex (MHC) class II antigen expression in the draining lymph node and the tumour during potentiation of the immune response by intralesional bacillus Calmette-Guérin (BCG) administration in the line 10 hepatocellular carcinoma in the strain 2 guinea-pig. Five days after its injection BCG induced a ninefold increase in the number of draining lymph node cells and an increased MHC class II expression. This increased MHC class II expression was mostly due to the selective increase of B cells in the lymph nodes, and to a lesser extent to the increase of T cells expressing MHC class II antigens. Taking into account this nine-fold increase, intralesional treatment of BCG increased considerably the number of T helper/inducer (anti-CT7) and T suppressor/cytotoxic (anti-CT6) lymph node cells expressing MHC class II antigen. The percentage of tumour-infiltrating T cells expressing MHC class II antigen in the tumour was higher than the percentage of T cells in the regional draining lymph node of non-treated guinea-pigs, indicating the presence of activated T cells in the tumour. After treatment with BCG no further increase in MHC class II expression was measured in the tumour, nor was any phenotypical change of the tumour-infiltrating T cells found. In conclusion, with the use of two-colour flow cytofluorometry we have shown that the potentiation of the already existing immune response to line 10 is accompanied by a considerable increase in T helper/inducer, T suppressor/cytotoxic cells and MHC class II antigen in the regional lymph node. Whether this is essential for the potentiation of the immune response causing tumour regression and long-lasting immunity is a subject for further study.

Effect of recombinant gamma interferon on hepatocellular carcinoma cell lines

The effects of recombinant gamma interferon (rIFN-gamma) were tested on 4 different hepatocellular carcinoma (HCC) cell lines PLC/PRF/5, HepG2, Hep3B and SK-Hep1. Exposure of these HCC cells to 100/ml of rIFN-gamma induced high levels of major histocompatibility complex (MHC) class I expression on their membrane, but not class II antigens. The enhancement of class I antigen synthesis occurs without a corresponding increase in synthesis of HBsAg by HBV genome positive PLC/PRF/5 and Hep3B cells. A 5 log dose of rIFN-gamma also did not trigger the integrated HBV genome into active replication as indicated by a lack of HBcAg and HBeAg synthesis. These results point to a possible role for the use of rIFN-gamma to enhance tumour cell recognition by the host immune system via the increased MHC class I expression.

Increased expression of major histocompatibility antigens in the liver as a result of cholestasis.

Increased expression of major histocompatibility complex (MHC) antigens may occur following liver transplantation. The mechanism by which this occurs is unclear. Postoperative complications may result in cholestasis. We have investigated the possibility that cholestasis may cause increased expression of MHC antigens in the liver. Cholestasis was induced in rat livers by bile duct ligation and transection. Total serum bilirubin rose markedly postoperatively and remained elevated over a period of 21 days. Samples of bile taken from rats were shown to remain sterile during the study period and there was no evidence of viral infection. Liver tissue taken 1, 3, 7, and 21 days postobstruction showed a marked increase in the expression of rat class I MHC antigens but not class II antigens. We suggest that cholestasis itself can induce increased MHC class I antigens in the liver. Therefore, if cholestasis occurs postoperatively in the human liver transplant recipient this might lead to increased expression of human class I MHC antigens and add to the overall cellular immune activity in a rejection reaction, although cholestasis probably cannot initiate rejection.

Simian immunodeficiency virus induces expression of class II major histocompatibility complex structures on infected target cells in vitro.

The human immunodeficiency virus (HIV) and the closely related simian immunodeficiency virus (SIV) induce profound immune dysfunction in primate species. The present studies show that cell populations infected in vitro with SIV exhibit increases in major histocompatibility complex (MHC) class II antigen expression. Cell lines chronically infected with both the monkey and human viruses express substantially more MHC class II but not more lineage-restricted or activation antigens on their membranes than do uninfected cell lines. Furthermore, 2'-deoxy-5-iodouridine increased MHC class II antigen expression on SIV-infected cell lines in parallel with increased expression of viral antigens. MHC class II induction does not appear to be mediated through the production of a soluble factor, such as gamma interferon, by SIV-infected cells. Interestingly, studies of the kinetics of antigen expression by cell lines after SIV infection indicate that the induction of MHC class II structures is a late event. Immunoelectron microscopy revealed that MHC class II antigen is expressed not only on the surfaces of the SIV-infected cells but also on the envelope of virus particles derived from those cells. MHC antigen expression on virus-infected cells and the expression of those determinants by the virus may play a role in the pathogenesis of acquired immunodeficiency syndrome and the autoimmune abnormalities observed in HIV-infected individuals.

Distinct effects of gamma interferon on human B-lymphocyte precursor cell lines.

The effect of gamma interferon (IFN-gamma) on proliferation and antigenic characteristics of cell lines belonging to the B-cell progenitor compartment was studied. We observed a selective effect of recombinant IFN-gamma but not IFN-alpha on proliferation of the B-precursor cell lines Reh and KM3. On day 4, after addition of 400 mu/ml IFN-gamma the [3H]thymidine uptake in these cells was reduced to 60% and 45% respectively, while no effect of IFN-gamma was evident on the proliferation of the more mature B-cell lines Raji, Ramos, B85, and Daudi. On the other hand, both Reh and Ramos showed induction of major histocompatibility complex (MHC) class I antigen expression in response to 400 mu/ml IFN-gamma. In contrast to 12-O-tetradecanoyl-phorbol-13-acetate (TPA), IFN-gamma did not induce increased MHC class II antigen expression on Reh cells. Taken together, our results indicate that IFN-gamma fulfils distinct functions at different levels in the development of B cells.