Association of plectin with Z-discs is a prerequisite for the formation of the intermyofibrillar desmin cytoskeleton

Plectin is a high-molecular mass protein (approximately 500 kd) that binds actin, intermediate filaments, and microtubules. Mutations of the plectin gene cause a generalized blistering skin disorder and muscular dystrophy. In adult muscle, plectin is colocalized with desmin at structures forming the intermyofibrillar scaffold and beneath the plasma membrane. To study the involvement of plectin in myofibrillogenesis, we analyzed the spatial and temporal expression patterns of plectin in cultured differentiating human skeletal muscle cells and its relationship to desmin intermediate filaments during this process. Northern and Western blot analyses demonstrated that at least two different plectin isoforms are expressed at all developmental stages from proliferating myoblasts to mature myotubes. Using immunocytochemistry, we show that the localization of plectin dramatically changes from a network-like distribution into a cross-striated distribution during maturation of myocytes. Double immunofluorescence experiments revealed that desmin and plectin are colocalized in premyofibrillar stages and in mature myotubes. Interestingly, plectin was often found to localize to the periphery of Z-discs during the actual alignment of neighboring myofibrils, and an obvious cross-striated plectin staining pattern was observed before desmin was localized in the Z-disc region. We conclude that the association of plectin with Z-discs is an early event in the lateral alignment of myofibrils that precedes the formation of the intermyofibrillar desmin cytoskeleton.

Alternative pathways for processing exogenous and endogenous antigens that can generate peptides for MHC class I-restricted presentation

The concept of distinct endogenous and exogenous pathways for generating peptides for MHC-I and MHC-II-restricted presentation to CD4+ or CD8+ T cells fits well with the bulk of experimental data. Nevertheless, evidence is emerging for alternative processing pathways that generate peptides for MHC-I-restricted presentation. Using a well characterized, particulate viral antigen of prominent medical importance (the hepatitis B surface antigen), we summarize our evidence that the efficient, endolysosomal processing of exogenous antigens can lead to peptide-loaded MHC-I molecules. In addition, we describe evidence for endolysosomal processing of mutant, stress protein-bound, endogenous antigens that liberate peptides binding to (and presented by) MHC-I molecules. The putative biological role of alternative processing of antigens generating cytotoxic T-lymphocyte-stimulating epitopes is discussed.

Priming MHC-I-restricted cytotoxic T lymphocyte responses to exogenous hepatitis B surface antigen is CD4+ T cell dependent

MHC-I (Ld)-restricted, S28-39-specific CTL responses are efficiently primed in H-2d BALB/c mice injected with low doses of native hepatitis B surface Ag (HBsAg) lipoprotein particles without adjuvants. Priming of this CTL response by exogenous HBsAg required CD4+ T cell "help" and IL-12: this CTL response could be neither induced in mice depleted of CD4+ T cells by in vivo Ab treatment, nor in (CD4+ T cell-competent or CD4+ T cell-depleted) IL-12-unresponsive STAT4-/- knockout BALB/c mice. Codelivery of oligonucleotides (ODN) with immunostimulating CpG sequences (ISS) with exogenous HBsAg reconstituted the CTL response to exogenous HBsAg in CD4+ T cell-depleted normal mice and in CD4+ T cell-competent and CD4+ T cell-depleted STAT4-/- BALB/c mice. Injection (by different routes) of "naked" pCI/S plasmid DNA encoding HBsAg into IL-12-responsive or -unresponsive BALB/c mice efficiently primed the MHC-I-restricted, HBsAg-specific CTL response. CTL priming was not detectable when CD4+ T cell-depleted animals were subjected to genetic immunization. In vivo priming of the well-characterized CD8+ CTL response to HBsAg in "high responder" BALB/c mice either by exogenous surface lipoprotein particles or by DNA vaccination is thus CD4+ T cell dependent. CTL priming by exogenous HBsAg, but not by genetic immunization, is IL-12 dependent. The dependence of CTL priming by exogenous HBsAg on CD4+ T cells can be overcome by codelivering ODN with ISS motifs, and this "adjuvants effect" operates efficiently in IL-12-unresponsive mice. The data characterize a feature of the adjuvant effect of ISS-containing ODN on CTL priming that may be of major interest for the design of CTL-stimulating vaccines with efficacy in immunodeficiency conditions.

Adjuvants that enhance priming of cytotoxic T cells to a Kb-restricted epitope processed from exogenous but not endogenous hepatitis B surface antigen

Intramuscular (i.m.) or s.c. injection of plasmid DNA encoding hepatitis B small surface antigen (HBsAg) primes potent MHC I-restricted cytotoxic T lymphocyte (CTL) responses in H-2(d) (BALB/c) and H-2(b) (C57BL/6) mice. In contrast, i.m. or s.c. injection of exogenous HBsAg particles without adjuvants primes CTL responses in 'high responder' H-2(d) but not 'low responder' H-2(b) mice. We have shown that processing of exogenous but not endogenous HBsAg generates the Kb-binding S208-215 peptide ILSPFLPL. This system allowed us to optimize conditions for stimulating murine CTL responses to exogenous antigen by identifying adjuvants that facilitate priming of Kb-restricted CTL by injecting recombinant HBsAg particles into 'low responder' H-2(b) mice. Synthetic oligodeoxynucleotides with immunostimulating sequences or the recombinant cytokine IL-12 efficiently enhanced priming of CTL to exogenous HBsAg. Hence, the adjuvanticity of DNA sequences that induce Th1 cytokines facilitate priming of MHC I-restricted T cell responses to exogenous antigen and are therefore of potential value in formulating vaccines designed to enhance CTL priming to exogenous antigen.

Malabsorption with progressive weight loss and multiple intestinal ulcers in a patient with T-cell lymphoma

We describe a 52-year-old woman who presented with severe diarrhea, nausea, intermittent abdominal pain and weight loss of 18 kg within ten months. Jejunal and duodenal ulcers were detected by endoscopy and multiple biopsies revealed villous atrophy of the jejunum. However, neither gliadin nor endomysium antibodies were detected and no clinical and histological improvement was achieved after gluten withdrawal. Despite strong clinical suspicion for intestinal lymphoma many unrevealing biopsies were done. The patient developed intermittent septic fever and diagnostic laparotomy revealed jejunal perforation. Partial jejunal resection was performed and histology confirmed the diagnosis of an intestinal T-cell lymphoma without celiac disease. Malabsorption and all intestinal ulcers disappeared during the course of chemotherapy (six cycles CHOP) and the patient recovered remarkably.

Tumour necrosis factor-alpha (TNF-alpha) transcription and translation in the CD4+ T cell-transplanted scid mouse model of colitis

The adoptive transfer of activated CD4+ alpha/beta T cell blasts from the spleens of immunocompetent C.B-17+/+ or BALB/cdm2 mice into C.B-17scid/scid (scid) mice induces a colitis in the scid recipient within 8 weeks, which progresses to severe disease within 16 weeks. T cells isolated from recipient colon show a Th1 cytokine phenotype. We have examined the relationship between the phenotype of the cellular infiltrate and the transcription and translation of the proinflammatory cytokine TNF-alpha. The techniques of double indirect immunohistology and in situ hybridization using digoxigenin-labelled riboprobes were used. The prominent myeloid cell infiltrate in diseased tissues comprised F4/80+, Mac-l+ macrophages, neutrophils, dendritic cells and activated macrophages. TNF-alpha transcription and translation were associated with activated macrophages in the lamina propria. Activated macrophages transcribing and translating TNF-alpha were clustered in areas of tissue destruction. Crypt epithelium of inflamed tissues transcribed TNF-alpha at a very early stage of the disease process, but translation of TNF-alpha protein could only be found in advanced epithelial dysplasia. This indicates differential post-transcriptional control of TNF-alpha in activated macrophages and the epithelium.

Truncated or chimeric endogenous protein antigens gain immunogenicity for B cells by stress protein-facilitated expression

Truncated variants of the SV40 large T antigen (T-Ag) with an intact N terminus are as efficiently expressed in eukaryotic transfectants as wild-type (wt) T-Ag. Coprecipitation of N-terminal T-Ag fragments with the constitutively expressed, cytosolic stress protein hsp73 suggests that this chaperone stabilized expression of the truncated T-Ag fragments. In contrast to T-Ag, the 163-residue N-terminal preS domain of the hepatitis B surface antigen (HBsAg) is difficult to express. When the preS domain is C-terminally fused to a hsp73-binding cytoplasmic T-Ag (cT-Ag) fragment its stable expression as a chimeric cT-preS protein is obtained. DNA-based vaccination with plasmid DNA encoding either wt or hsp-associated mutant T-Ag elicited potent MHC class I-restricted, T-Ag-specific T cell responses. In contrast, DNA vaccination with hsp73-binding (mutant or chimeric) T-Ag variants, but not with wt T-Ag elicited T-Ag-specific antibody responses. Furthermore, vaccination with cT-preS-encoding plasmid DNA induced antibodies binding to the preS domain of the large HBsAg. Hence, hsp73-bound endogenous antigens efficiently stimulate antibody responses. These findings may be relevant for tumor immunology and autoimmunity.

Purification and characterization of hepatitis B virus surface antigen particles produced in Drosophila Schneider-2 cells

The small surface antigen of hepatitis B virus (HBV) was produced in Drosophila melanogaster Schneider-2 (DS-2) cells transfected stably using an inducible Drosophila metallothionein promoter. Selected clonal DS-2 cell-lines expressed and secreted large quantities of HBsAg particles consisting exclusively of non-glycosylated 25 kDa proteins. HBsAg produced by DS-2 cells had physical and biochemical properties very similar to 22 nm particles derived from the human hepatoma cell-line PLC/PRF/5. DS-2 cell-derived HBsAg particles were purified near homogeneity by a strategy based on protein concentration, precipitation and ultracentrifugation. The resulting HBsAg product was < 98% pure. A single immunisation of BALB/c mice with both DS-2 and yeast-cell derived purified HBsAg particles without adjuvants elicited a substantial humoral antibody and class-I restricted cytotoxic T lymphocyte (CTL) response. Adsorption of HBsAg particles to aluminium hydroxide resulted in increased levels of HBsAg-specific antibodies. However, CTLs were not elicited by HBsAg/Alum combinations. Thus, stably transfected DS-2 cells provide a useful source for the production of HBV subviral particles for diagnostic and research purposes as well as for novel vaccine development.

Colitis-inducing potency of CD4+ T cells in immunodeficient, adoptive hosts depends on their state of activation, IL-12 responsiveness, and CD45RB surface phenotype

We studied the induction, severity and rate of progression of inflammatory bowel disease (IBD) induced in SCID mice by the adoptive transfer of low numbers of the following purified BALB/c CD4+ T cell subsets: 1) unfractionated, peripheral, small (resting), or large (activated) CD4+ T cells; 2) fractionated, peripheral, small, or large, CD45RBhigh or CD45RBlow CD4+ T cells; and 3) peripheral IL-12-unresponsive CD4+ T cells from STAT-4-deficient mice. The adoptive transfer into SCID host of comparable numbers of CD4+ T cells was used to assess the colitis-inducing potency of these subsets. Small CD45RBhigh CD4+ T lymphocytes and activated CD4+ T blasts induced early (6-12 wk posttransfer) and severe disease, while small resting and unfractionated CD4+ T cells or CD45RBlow T lymphocytes induced a late-onset disease 12-16 wk posttransfer. SCID mice transplanted with STAT-4-/- CD4+ T cells showed a late-onset IBD manifest > 20 wk posttransfer. In SCID mice with IBD transplanted with IL-12-responsive CD4+ T cells, the colonic lamina propria CD4+ T cells showed a mucosa-seeking memory/effector CD45RBlow Th1 phenotype abundantly producing IFN-gamma and TNF-alpha. In SCID mice transplanted with IL-12-unresponsive STAT-4-/- CD4+ T cells, the colonic lamina propria, mesenteric lymph node, and splenic CD4+ T cells produced very little IFN-gamma but abundant levels of TNF-alpha. The histopathologic appearance of colitis in all transplanted SCID mice was similar. These data indicate that CD45RBhigh and CD45RBlow, IL-12-responsive and IL-12-unresponsive CD4+ T lymphocytes and lymphoblasts have IBD-inducing potential though of varying potency.

DNA immunization confers systemic, but not mucosal, protection against enteroinvasive bacteria

Naked plasmid DNA (pRc/Y-hsp60) with a cytomegalovirus promoter and a sequence encoding Yersinia enterocolitica 60-kDa heat shock protein (Y-HSP60) was used for vaccination. After intramuscular injection of pRc/Y-hsp60, Y-hsp60 mRNA could be detected by reverse transcription-PCR in muscle, liver and spleen. A single immunization with pRc/Y-hsp60 induced significant Y-HSP60-specific T cell responses after 1 week. IFN-gamma production by spleen cells upon stimulation with Y-HSP60 was strictly dependent on the presence of CD4+ T cells, indicating the generation of a Th1 response upon DNA immunization. DNA immunization in addition induced strong Y-HSP60-specific IgG2a, weak IgG1, but not IgA antibodies. Immunization of BALB/c and C57BL/6 mice with pRc/Y-hsp60 conferred protection against disseminated Y. enterocolitica infection in spleen, but not at the site of mucosal entry, the Peyer's patches. Furthermore, pRc/Y-hsp60 vaccination did not induce cross-protection against related pathogens. Vaccination of beta2-microglobulin- and H2-I-Abeta-deficient mice was not protective, suggesting that both CD4+ and CD8+ T cells are required for protective immunity induced by DNA vaccination.

Enhancing the immunogenicity of exogenous hepatitis B surface antigen-based vaccines for MHC-I-restricted T cells

Vaccination with either exogenous hepatitis B surface antigen (HBsAg) lipoprotein particles without adjuvants, or plasmid DNA encoding secreted small HBsAg stimulate long-lasting, potent antibody responses in H-2d (BALB/c) and C57Bl/6 (H-2b) mice. Vaccination with exogenous HBsAg primes MHC-I restricted cytotoxic T lymphocyte (CTL) responses to HBsAg in H-2d but not H-2b mice, while DNA vaccination primes HBsAg-specific CTL responses in both mouse strains. We defined vaccination strategies that could elicit CTL responses to exogenous HBsAg in 'low responder' C57Bl/6 mice. We found that the bacterial plasmid DNA itself, synthetic oligodeoxynucleotides containing immunostimulating sequences, or recombinant Th1 cytokines (IL12, IFNgamma) efficiently support priming of CTL responses to exogenous HBsAg in 'low responder' H-2b mice, but have only minor effects on CTL priming in 'high responder' H-2d mice in the high dose range tested. These molecularly well defined adjuvants can thus efficiently support priming of anti-viral T cell responses under 'low responder' conditions.

Immunostimulatory CpG motifs trigger a T helper-1 immune response to human immunodeficiency virus type-1 (HIV-1) gp 160 envelope proteins

Bacterial DNA sequences containing unmethylated CpG motifs have recently been proposed to exhibit immunostimulatory effects on B-, T- and NK cells, leading to the induction of humoral and cell-mediated immune responses. In the present study we investigated the immunomodulatory effects of a CpG-containing oligodeoxynucleotide (CpG ODN) to the HIV-1 gp 160 envelope (Env) protein in the BALB/c mouse model. Priming and boosting of mice with gp 160 adsorbed to aluminium hydroxide (Alum) induced a typical T helper-2 (Th2)-dominated immune response with high titers of gp 160-specific immunoglobulin (Ig)G1 isotypes but a weak IgG2a response. Specifically re-stimulated splenocytes from these mice predominantly secreted interleukin (IL)-5 but only minute amounts of interferon-gamma (IFN-gamma) upon specific re-stimulation. In contrast, a boost immunisation of gp 160/Alum primed mice with a gp 160/Alum/CpG combination resulted in a seven times higher production of IgG2a antibodies, without affecting the titers of IgG1 isotypes. Furthermore, approximately 10-fold increased levels of IFN-gamma, but significantly reduced amounts of IL-5, were secreted from gp 160-restimulated splenic cells. A further greater than 30-fold increase in the levels of specific IgG2a responses and a substantially elevated secretion of IFN-gamma were observed when the mice received gp160/Alum/CpG combinations for priming and boost injections. Thus, CpG ODNs are useful as an adjuvant to induce a typical Th0/Th1 response to HIV gp 160 proteins. However, despite the induction of a more Th1-like immune response, gp 16O/Alum/CpG combinations were not sufficient to prime an Env-specific cytotoxic T-cell (CTL) response.

Similar as well as distinct MHC class I-binding peptides are generated by exogenous and endogenous processing of hepatitis B virus surface antigen

Murine MHC class I-restricted cytotoxic T lymphocyte (CTL) responses can be primed by exogenous as well as endogenous hepatitis B surface antigen (HBsAg). Immunodominant CTL-defined epitopes of this viral envelope protein are the Ld-binding 12-mer S28-39 peptide IPQSLDSWWTSL in H-2d mice, and the Kb-binding 8-mer S208-215 peptide ILSPFLPL in H-2b mice. We tested if CTL recognizing these epitopes can be primed in vivo by HBsAg delivered as either an exogenous antigen (native HBsAg lipoprotein particles), or an endogenous antigen (plasmid DNA encoding HBsAg). Primed T cells were restimulated in vitro prior to the cytotoxicity assay with cells presenting the H-2 class I-binding epitopes generated by either exogenous or endogenous processing of HBsAg. The data indicate that the Ld-binding peptide S28-39 is generated during exogenous as well as endogenous processing of HBsAg. In contrast, the Kb-binding peptide S208-215 is generated during exogenous but not endogenous processing of HBsAg. Hence, some but not all MHC class I-binding, immunogenic peptides are generated during endogenous and exogenous processing of HBsAg but there also exists a repertoire of immunogenic peptides of viral origin that is only revealed after exogenous processing of viral proteins.

Immunization of woodchucks with plasmids expressing woodchuck hepatitis virus (WHV) core antigen and surface antigen suppresses WHV infection

DNA vaccination can induce humoral and cellular immune response to viral antigens and confer protection to virus infection. In woodchucks, we tested the protective efficacy of immune response to woodchuck hepatitis core antigen (WHcAg) and surface antigen (WHsAg) of woodchuck hepatitis virus (WHV) elicited by DNA-based vaccination. Plasmids pWHcIm and pWHsIm containing WHV c- or pre-s2/s genes expressed WHcAg and WHsAg in transient transfection assays. Pilot experiments in mice revealed that a single intramuscular injection of 100 microgram of plasmid pWHcIm DNA induced an anti-WHcAg titer over 1:300 that was enhanced by boost injections. However, two injections of 100 microgram of pWHcIm did not induce detectable anti-WHcAg in woodchucks. With an increase in the dose to 1 mg of pWHcIm per injection, transient anti-WHcAg response and WHcAg-specific proliferation of peripheral mononuclear blood cells (PMBCs) appeared in woodchucks after repeated immunizations. Four woodchucks vaccinated with pWHcIm were challenged with 10(4) or 10(5) of the WHV 50% infective dose. They remained negative for markers of WHV replication (WHV DNA and WHsAg) in peripheral blood and developed anti-WHs in week 5 after challenge. In contrast, woodchucks not immunized or immunized with the control vector pcDNA3 developed acute WHV infection. Two woodchucks immunized with 1 mg of pWHsIm developed WHsAg-specific proliferative response of PBMCs but no measurable anti-WHsAg response. A rapid anti-WHsAg response developed during week 2 after virus challenge. Neither woodchuck developed any signs of WHV infection. These data indicate that DNA-based vaccination with WHcAg and WHsAg can elicit immunity to WHV infection.

Similar as well as distinct MHC class I-binding peptides are generated by exogenous and endogenous processing of hepatitis B virus surface antigen

Murine MHC class I-restricted cytotoxic T lymphocyte (CTL) responses can be primed by exogenous as well as endogenous hepatitis B surface antigen (HBsAg). Immunodominant CTL-defined epitopes of this viral envelope protein are the Ld-binding 12-mer S28-39 peptide IPQSLDSWWTSL in H-2d mice, and the Kb-binding 8-mer S208-215 peptide ILSPFLPL in H-2b mice. We tested if CTL recognizing these epitopes can be primed in vivo by HBsAg delivered as either an exogenous antigen (native HBsAg lipoprotein particles), or an endogenous antigen (plasmid DNA encoding HBsAg). Primed T cells were restimulated in vitro prior to the cytotoxicity assay with cells presenting the H-2 class I-binding epitopes generated by either exogenous or endogenous processing of HBsAg. The data indicate that the Ld-binding peptide S28-39 is generated during exogenous as well as endogenous processing of HBsAg. In contrast, the Kb-binding peptide S208-215 is generated during exogenous but not endogenous processing of HBsAg. Hence, some but not all MHC class I-binding, immunogenic peptides are generated during endogenous and exogenous processing of HBsAg but there also exists a repertoire of immunogenic peptides of viral origin that is only revealed after exogenous processing of viral proteins.

Proliferation and apoptosis of lamina propria CD4+ T cells from scid mice with inflammatory bowel disease

Scid mice transplanted with low numbers of syngeneic CD4+ T cells, develop a chronic and lethal inflammatory bowel disease (IBD) within 4-6 months. We have used in vivo 5-bromo2-deoxy-uridine (BrdU) labeling to assess the proliferation of lamina propria-derived CD4+ T cells in diseased scid mice. The hourly rate of renewal of colonic lamina propria CD4+ T cells in diseased mice was 7% compared with 1.5% in normal BALB/c control mice. Transplantation of scid mice with in vitro activated CD4+ T cells accelerated the disease onset and development in a cell dose-dependent fashion when compared with non-activated CD4+ T cells. In pulse-chase experiments it was shown that BrdU-labeled cells disappeared rapidly from the lamina propria of diseased mice. DNA analysis revealed that this was due to the presence of nearly four times as many apoptotic CD4+ T cells in diseased than in control mice. Further analyses showed that the apoptotic lamina propria CD4+ T cells were derived from cells having entered the cell cycle within the previous 8 h. These data clearly demonstrate that vigorous CD4+ T cell proliferation and death are involved throughout the course of IBD.

DNA vaccination with glutamic acid decarboxylase (GAD) generates a strong humoral immune response in BALB/c, C57BL/6, and in diabetes-prone NOD mice

The technique of DNA-based vaccination was used to generate a T-cell-dependent antibody response to glutamic acid decarboxylase (GAD) in BALB/c, C57BL/6, and non-obese diabetic (NOD) mice. Plasmids were constructed in which the expression of the rat GAD65 (rGAD65) or the rat GAD67 (rGAD67) gene was driven by the immediate early region promoter of the human cytomegalovirus (pCMV). This "naked" plasmid DNA was then injected into the regenerating muscles of the studied mice. In the vaccinated animals, antibody responses to GAD65 or to GAD67 were induced. Epitope recognition of GAD was studied by protein footprinting, a technique which makes use of a limited proteolysis of antibody-bound antigen. Different epitope recognition patterns were found, corresponding to strain-specific patterns. Mild trypsin treatment generated 50 kD, 46 kD, 40 kD, 30 kD, and 21 kD proteolytic fragments. In NOD mice, 50, 46 and 40 kD bands were the most prominent signals. In non-diabetes prone BALB/c mice, a faint 40 kD band appeared suggesting a rather weak protection of GAD from tryptic lysis. The pattern observed in C57BL/6 mice was more comparable to the NOD mice pattern with prominent 40 kD and 30 kD signals and a faint 21 kD fragment. Diabetes incidence was unchanged in NOD mice, and no diabetes was observed in C57BL/6 and BALB/c mice, respectively. The data demonstrate that genetic immunization is a suitable novel tool to stimulate and to manipulate an immune response against the diabetes-associated protein glutamic acid decarboxylase. Interestingly, our results indicate that, by genetic vaccination, distinct B-cell epitopes were generated in the various studied mouse strains.

Natural occurrence of Fusarium toxins in oats harvested during five years in an area of southwest Germany

A total of 56, 56, 54, 51, and 55 oats samples used for feed production were collected randomly after the 1987, 1989, 1990, 1991 and 1992 crops, respectively, from farms located in an area of southwest Germany. Deoxynivalenol (DON), 3- and 15-acetyl-deoxynivalenol (3-, 15-ADON), nivalenol (NIV), fusarenon-X (FUS-X), T-2 toxin (T-2), HT-2 toxin (HT-2) and diacetoxyscirpenol (DAS) were determined by gas chromatography with mass selective detection (GC-MS), zearalenone (ZEA), alpha and beta-zearalenol (alpha-, beta-ZOL) by GC-MS or by HPLC. DON was the major toxin with incidences at 49-85% and mean levels in positive samples of 52-302 micrograms/kg. Incidences of ZEA, 3-ADON, NIV, HT-2, and T-2 were at 20-37, 0-30, 18-67, 0-29, and 27-61%, respectively, with mean levels in positive samples at 8-25, 5-63, 11-192, 205-296, and 20-244 micrograms/kg, respectively. alpha- and beta-ZOL and DAS were not detected in any sample. 15-ADON and FUS-X were assayed in samples from 1987, 1991 and 1992. 15-ADON was detected in 9, 4 and 0% of samples, with an average of 9 and 18 micrograms/kg, respectively; FUS-X was not detected. The incidence and levels of toxins varied from year to year. The correlation between the occurrence of toxins and precipitation is discussed.

Accumulation of immunoglobulin-containing cells in the gut mucosa and presence of faecal immunoglobulin in severe combined immunodeficient (scid) mice with T cell-induced inflammatory bowel disease (IBD)

Scid mice transplanted either with a gut wall graft or with low numbers of purified CD4+ T cells from immunocompetent syngeneic donor mice show clinical signs of IBD 3-4 months post-transplantation. The disease is mediated by mucosa-infiltrating CD4+ TCR alphabeta+ T cells. The pathology of 52 individual colon segments obtained from 20 gut wall- or CD4+ T cell-transplanted diseased scid mice was evaluated by histology and the numbers of infiltrating immunoglobulin-containing cells were determined. In particular, cells positive for IgM, IgA and non-inflammatory immunoglobulin isotypes such as IgG1 and IgG2b were found to accumulate in colon segments displaying the most severe histopathology, including inflammatory cellular infiltration, epithelial hyperplasia and ulcerative lesions. Compared with colon segments of normal C.B-17 mice, the lesional scid colon shows increased levels of cells positive for the IgG classes. Faecal extracts of the CD4+ T cell-transplanted scid mice revealed the presence of all six murine immunoglobulin isotypes. Disease progression was accompanied by an increased level of excreted IgM and IgG3 and decreased levels of IgA. It is concluded that locally secreted immunoglobulins may play an immunomodulating role in the pathological changes observed in the present model of T cell-induced inflammatory bowel disease.

T cell-mediated, IFN-gamma-facilitated rejection of murine B16 melanomas

The murine melanoma cell line B16.F10 (H-2b) was used to study specific T cell responses that reject tumors. Stable B16 transfectants were established that express viral Ags, either the hepatitis B surface Ag (HBsAg) or the large tumor Ag (T-Ag) of SV40. B16 cells and their transfected sublines were CD40+ CD44+ but expressed no (or low levels of the) costimulator molecules CD154 (CD40L), CD48, CD54, CD80, and CD86. Surface expression of MHC class I (Kb, Db) and class II (I-Ab) molecules by B16 cells was low, but strikingly up-regulated by IFN-gamma. CD95 (Fas) and CD95 ligand (CD95L (FasL)) were "spontaneously" expressed by B16 cells growing in vitro in serum-free medium; these markers were strikingly up-regulated by IFN-gamma. B16 cells coexpressing CD95 and CD95L were irreversibly programmed for apoptosis. In vitro, noninduced B16 transfectants stimulated a specific IFN-gamma release response, but no cytolytic response (in a 4-h assay) in MHC class I-restricted CTL; in contrast, IFN-gamma-induced B16 targets were efficiently and specifically lysed by CTL. In vivo, B16 transfectants were specifically rejected by DNA-vaccinated syngeneic hosts through a T-dependent immune effector mechanism. The tumors showed evidence of massive apoptosis in vivo during the rejection process. The data suggest that CTL-derived IFN-gamma enhances an intrinsic suicide mechanism of these tumor cells in addition to facilitating lytic interactions of effectors with tumor targets.

Cytokine and hepatitis B virus DNA co-immunizations enhance cellular and humoral immune responses to the middle but not to the large hepatitis B virus surface antigen in mice

Genetic immunization is a potentially useful strategy to prevent or treat hepatitis B virus (HBV) infection. We have previously shown that HBV envelope proteins are highly immunogenic using this technique. The large envelope protein (LHBs), however, induced significantly weaker humoral and cellular immune responses when compared with the middle envelope protein (MHBs). We studied the effect of co-immunizations with cytokine DNA expression constructs encoding for interleukin (IL)-2 and (GM-CSF) on the immunogenicity of LHBs at the B-and T-cell level. Co-immunizations of mice with plasmids encoding for MHBs and IL-2 or GM-CSF increased anti-HBs responses, helper T-cell proliferative activity, and cytotoxic T lymphocyte (CTL) killing. In contrast, co-immunizations of plasmids encoding for LHBs and IL-2 or GM-CSF had no effect on humoral and cellular immune responses. LHBs did not inhibit the production or secretion of IL-2 and GM-CSF. In addition, IL-2, tumor necrosis factor alfa (TNF-alpha), and interferon gamma (IFN-gamma) had no suppressive effect on HBV envelope protein expression in vitro. Based on these data, MHBs, but not LHBs, genetic immunization can be augmented by IL-2 or GM-CSF cytokines.

A pancolitis resembling human ulcerative colitis (UC) is induced by CD4+ TCR alphabeta T cells of athymic origin in histocompatible severe combined immunodeficient (SCID) mice

CD4+ TCRalphabeta+ T cells from the colonic lamina propria of athymic (nude) mice were adoptively transferred into histocompatible (SCID) mice homozygous for the autosomal recessive mutation scid (severe combined immunodeficiency). Transfer of these extrathymic CD4+ T cells into SCID mice induced a pancolitis in the adoptive host. The histopathology of this inflammatory response was restricted to the colon and closely resembled human UC. CD4+ T cells infiltrating the colonic lamina propria of diseased SCID mice displayed the surface phenotype of mucosa-seeking memory/effector cells, expressed interferon-gamma (IFN-gamma), and lysed targets in a Fas (CD95)/FasL-dependent pathway. Massive accumulation of oligoclonal CD4+ T cells of athymic origin with the phenotype of Th1 memory/effector T cells in the colonic lamina propria of a histocompatible, immunodeficient host elicits a pancolitis that morphologically mimics human UC.

Expression of selectin-binding epitopes and cytokines by CD4+ T cells repopulating scid mice with colitis

Recruitment into the gut of CD4+ T cells and their activation in the colonic lamina propria (LP) are key events in the development of colitis in scid mice reconstituted with CD4+ T cells from immunocompetent, congenic donor mice. This study investigated the expression of cytokines and selectin-binding epitopes by CD4+ T cells repopulating different tissues of the adoptive scid host. Cells from the inflamed colonic LP of transplanted scid mice produced high amounts of IL-12, IFN-gamma and TNF-alpha but only low amounts IL-4 and IL-10. Intracellular cytokine staining confirmed the presence of large numbers of IFN-gamma- and TNF-alpha-producing effector CD4+ T cells in the colonic LP of scid mice with colitis but also in non-inflamed tissues [spleen (S), peritoneal cavity (PC) and mesenteric lymph nodes (mLN)] of the adoptive host. Cells from these tissues furthermore produced large amounts of IL-12. Ligands for endothelial selectins are involved in recruiting T cells into inflamed tissues. We have analyzed the expression of selectin-binding epitopes on CD4+ T cells repopulating different tissues of the adoptive scid host. We found that a large fraction of CD4+ T cells from inflamed colonic LP and from non-inflamed PC, mLN and S expressed high levels of P- and E-selectin-binding epitopes (P-Lhi) in transplanted scid mice, but not in congenic, immunocompetent control mice. Although P-Lhi CD4+ T cells were enriched in IFN-gamma-producing subsets from most (but not all) tissues, we also found large numbers of in vivo generated P-Llo CD4+ T cells producing pro-inflammatory cytokines. This was in contrast to in vitro generated Th1 CD4+ T blasts that were almost exclusively P-Lhi. In this mouse model, production of Th1-type pro-inflammatory cytokines and expression of surface epitopes binding endothelial selectins are hence strikingly up-regulated in CD4+ T cells residing in inflamed and non-inflamed tissues during the development of colitis.