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T H The

Publications and source records attributed to T H The.

At least 91 records · Page 5Linked to original sources
PubMed1993

Magnetite as a potent contrast-enhancing agent in magnetic resonance imaging to visualize blood-brain barrier disruption.

Imaging of blood-brain barrier damage by magnetic resonance was currently studied as to the potential of dextran-magnetite particles (DMP) for contrast enhancement. For that purpose, dextran-T10 (average molecular weight: 10.9 Kilodalton) was complexed with magnetite (Fe3O4) in ammonia. Experimental testing of the agent was made in vivo using Wistar rats with a freezing injury to the brain. DMP was i.v. injected at a dose of 90 microM Fe/kg b.w. followed by 2% Evans blue (0.6 ml). Control animals with trauma were studied without administration of DMP. Histochemical assessments were made to analyze the tissue distribution of DMP in the brain, kidney and liver after fixation in 4% formalin. MR imaging was conducted with 1.5 Tesla field strength with a circular coil 15 min after the freezing insult and administration of DMP. T1- and T2-weighted images were obtained using spin echo sequences among others. Regression analyses indicated a 50% reduction of T1 at a DMP concentration of 48 microM Fe, while for T2 only 4 microM/Fe(DMP) were sufficient for a 50% reduction. DMP was also accumulating in other organs, particularly in the Kupffer cells of the liver. Administration of DMP led to recognition of the freezing lesion as black area in agreement with macroscopical findings obtained by autopsy. In animals with a freezing lesion without administration of DMP, only T2-weighted images demonstrated a somewhat higher intensity attributable to the disruption of the blood-brain barrier. The present findings demonstrate the usefulness of DMP for contrast enhancement of lesions following disruption of the blood-brain barrier.

Animals↗
PubMed1993

Intracerebral and subcutaneous xenografts of human SCLC in the nude rat: comparison of monoclonal antibody localization and tumor infiltrating lymphocytes.

In the WAG/Rij nude rat, subcutaneous (s.c.) and intracerebral (i.c.) xenografts of the human SCLC cell line GLC-28 were evaluated for their growth behavior, in vivo monoclonal antibody binding and presence of tumor infiltrating lymphocytes. For the i.c. xenografts, two models of cerebral tumor growth were studied, one in the cerebral cortex and one in the lateral ventricle of the brain. In the s.c. and both i.c. xenografts models, in vivo localization of anti-carcinoma moab MOC-31 occurred within 4 hours after i.p. injection, with a maximal binding at 24 h after injection. A pronounced tumor infiltration of predominantly NK cells was observed for s.c. and intraventricular xenografts, but not for the GLC-28 tumors xenografted in the cerebral cortex. The presented nude rat/GLC-28 xenograft models may be used for the in vivo testing of experimental imaging techniques or alternative treatment strategies relevant to brain metastases of human SCLC.

Animals↗
PubMed1993

Local antitumour treatment in carcinoma patients with bispecific-monoclonal-antibody-redirected T cells.

In a pilot clinical study carcinoma patients with malignant ascites or pleural exudates have been treated locally with autologous lymphocytes activated ex vivo and redirected towards tumour cells with bispecific monoclonal antibodies. BIS-1, the bispecific monoclonal antibody used in this study, combines specificity against a tumour-associated antigen, AMOC-31, present on carcinomas, with a specificity against the CD3 complex on T lymphocytes. Patients selected for treatment had malignant pleural or peritoneal effusions. Treatment consisted of isolating autologous peripheral blood lymphocytes, ex vivo activation, incubation with bispecific monoclonal antibodies and injection at the effusion site of these BIS-1-redirected lymphocytes. To evaluate the effects of the bispecific monoclonal antibody, five patients received treatments with activated lymphocytes without bispecific antibodies. Effusion samples taken before and at various times after treatment were analysed by immunocytology and for the presence of the soluble factors carcinoembryonic antigen (CEA), interleukin-6 (IL-6), tumour necrosis factor (TNF), C-reactive protein and soluble CD8. In this way both immune activation and anti-tumour activity could be monitored. Conjugate formation between tumour cells and activated lymphocytes was seen as soon as 4 h after injection of BIS-1-redirected activated lymphocytes, followed by a disappearance or reduction of tumour cells after 24-48 h. In parallel with this, the soluble tumour marker CEA decreased in the effusion fluid following injection with the BIS-1-redirected lymphocytes. Furthermore, a steep increase in local granulocyte numbers was observed in the effusion fluid, which reached a maximum 24-48 h after the start of the treatment. Also levels of IL-6 and TNF were greatly elevated. The data suggest that the treatment induces both antitumour activity and a strong local inflammatory reaction. This is accompanied by no or only minor local and systemic toxicity, i.e. mild fever, which disappeared as the local inflammatory reaction diminished 48-72 h after treatment.

Abdominal Neoplasms↗
PubMed1993

HLA-Dr-expressing CD8bright cells are only temporarily present in the circulation during subcutaneous recombinant interleukin-2 therapy in renal cell carcinoma patients.

The effect of subcutaneous recombinant interleukin-2 (rIL-2) therapy on the "activation status" of peripheral blood lymphocytes (PBL) of 17 renal cell carcinoma patients was investigated in a longitudinal study. The expression of the activation markers HLA-Dr and CD25 on cytotoxic T cells, helper T cells, and natural killer (NK) cells, was analysed using two-colour flow cytometry of whole-blood samples. In addition, the ability of isolated PBL to proliferate in vitro in response to various stimuli was investigated. The absolute amounts of NK cells and HLA-DR-expressing NK cells increased continuously during the whole course of therapy. The absolute amounts of T cells and HLA-Dr-expressing T cells, however, showed an early increase only during the first 1 or 2 weeks of therapy, after which the absolute amounts of HLA-Dr-expressing T cells decreased. In particular, the absolute amount of HLA-Dr-expressing CD8bright+ T cells was significantly lowered in the second half of therapy. PBL collected on day 7 of therapy (post-cycle-1 PBL) showed, as compared to those collected prior to therapy (pretherapy PBL), a decreased proliferative response in vitro after stimulation with phytohaemagglutinin, concanavalin A, soluble CD3 mAb (WT32) or rIL-2. This decreased in vitro response of post-cycle-1 PBL was also reflected in a decrease in the percentage of CD8bright+ T cells expressing HLA-Dr in cultures with rIL-2 or CD3 mAb, in contrast to cultures of pretherapy PBL, which showed an increase of this percentage. We conclude that T cells are the predominantly stimulated subpopulation during the first 2 weeks of subcutaneous rIL-2 therapy. The significant decrease in the absolute amounts of HLA-Dr-expressing T cells in the peripheral blood during the second half of therapy may partly be explained by a decreased responsiveness to rIL-2, but a selective redistribution of HLA-Dr-expressing cells may also be involved.

Adult↗
PubMed1993

Our approach towards developing a specific tumour-targeted MRI contrast agent for the brain.

This review presents various aspects of the technological development, and their assessment in the design of a contrast agent for MRI, tailored to visualise tumours in the brain. First, it was demonstrated that magnetite as a contrast agent exhibited a much stronger relaxivity than gadolinium. The prepared magnetite particles bound to dextran, were also shown to be of appropriate size by electron microscopy. After their intravenous injection into rats with blood-brain barrier disruption, the lesion was strongly enhanced by T2-shortening. Furthermore, monoclonal antibodies directed against small cell lung carcinoma, proved to be able to penetrate into tumours, which had been raised by implantation of the small cell lung carcinoma cells into the brains of nude rats. As to the essential step, it was demonstrated in vitro that magnetite particles coupled to monoclonal antibodies by the biotin-streptavidin binding, could be bound to the target cells of the antibody, changing the relaxation rates of the latter. Finally it could be shown in vitro that an alternative approach, using lymphocytes to be targeted to tumour cells, also proved feasible, in that these lymphocytes could be labelled with magnetite that had been incorporated into liposomes. Further developments will be the in vivo assessment of the acquired progress in experimental animals, before clinical application is warranted.

Animals↗
PubMed1993

Radioimmunodetection of human small cell lung carcinoma xenografts in the nude rat using 111in-labelled monoclonal antibody MOC-31.

The applicability of mouse monoclonal antibody MOC-31 for in vivo radioimmunodetection of human small cell lung cancer (SCLC) was investigated in a nude rat xenograft model. MOC-31 is reactive with a 38 kD pancarcinoma membrane antigen. [111In]DTPA-MOC-31 showed good in vivo immunolocalisation to xenografted SCLC cells, whereas antigen-related uptake was low in normal rat tissues and in a control antigen-negative, human-derived tumour. Non-antigen-related uptake in the liver could be blocked by pretreatment with irrelevant antibody. It is concluded that MOC-31 can be used for radioimmunodetection of SCLC in vivo and may be suitable as a targeting device in patients.

Animals↗
PubMed1993

Circulating cytomegalovirus (CMV)-infected endothelial cells in patients with an active CMV infection.

In 10 of 14 patients with an active cytomegalovirus (CMV) infection, distinctive large cells (35-45 microns in diameter) were present in the peripheral blood. Morphologically these cells closely resembled the classic cytomegalic inclusion cells, generally regarded as a diagnostic hallmark of CMV infection. Moreover, these cells were shown to express CMV antigens belonging to all three stages of the viral replication cycle, indicating a productive CMV infection. In addition, immunologic staining with monoclonal antibodies directed against cell differentiation and marker proteins showed that these circulating cytomegalic cells were of endothelial origin. The presence of CMV-infected endothelial cells in the peripheral blood of patients with an active CMV infection indicates that such an infection might be accompanied by widespread occult vascular damage.

AIDS-Related Opportunistic Infections↗
PubMed1993

Ultrastructural analysis of circulating cytomegalic cells in patients with active cytomegalovirus infection: evidence for virus production and endothelial origin.

The presence of cytomegalic inclusion cells in the peripheral blood of patients with an active cytomegalovirus infection has recently been demonstrated. Immunologic staining showed that these cells were of endothelial origin. Study of circulating cytomegalic cells by transmission electron microscopy showed the cells to be productively infected with cytomegalovirus. Viral capsids were present in the nucleus and virus particles and dense bodies were found in the cytoplasm. The results indicate that these circulating cytomegalic cells could disseminate cytomegalovirus throughout the body. In addition, the finding of a cluster of cytomegalic cells in the peripheral blood linked together by zonula adherens type cell junctions is further evidence that these cells are of endothelial origin and suggests that the endothelial damage may be extensive.

Cell Nucleus↗
PubMed1993

Prediction of recurrent cytomegalovirus disease after treatment with ganciclovir in solid-organ transplant recipients.

CMV disease often recurs after initially successful antiviral therapy. We retrospectively determined in a group of 36 organ transplant patients whether clinical, virological, or immunological parameters during or shortly after cessation of antiviral therapy can identify those at high risk of relapse. Eleven of 36 patients had recurrent CMV disease after ganciclovir therapy. Neither donor or recipient CMV serostatus, type of baseline immunosuppression, antirejection treatment, indication for antiviral treatment, nor presence of CMV in the blood during or after therapy (as detected by antigenemia, viremia, or a positive polymerase-chain-reaction signal) were helpful in identification of patients with subsequent relapse. However, quantitative monitoring of antigenemia fascilitated early diagnosis of relapse since 10 of 11 patients with > or = 10 antigen-positive cells per 50,000 PMNs relapsed (99.1%, 95% CI 58.7-99.8). IgM and IgG responses against CMV during primary infection were comparable in relapsing and nonrelapsing patients. During secondary infection relapse occurred only in the 4 patients with the lowest IgG responses. The number of activated CD8bright lymphocytes in the peripheral blood as determined by flow cytometry at the end of antiviral therapy was a strong risk factor for the subsequent clinical course: 6 of 7 patients (85.7%, 95% CI 42.1-99.6%) with < 100 x 10(3) HLADR+CD8bright cells/ml blood relapsed, while 8 of 8 (100%, 95% CI 63-100) with activated CD8bright cells above that level remained asymptomatic (P < .025). These data show that patients with a high risk of relapse of CMV disease can be identified at the end of antiviral therapy.

Antibody Formation↗
PubMed1993

Cytomegalovirus antigenemia: clinical correlations in transplant recipients and in persons with AIDS.

We evaluated a rapid immunoperoxidase technique for the detection of cytomegalovirus (CMV) antigenemia in peripheral blood neutrophils of 56 transplant recipients (117 specimens) and 36 persons with AIDS (59 specimens). Antigenemia was 92% sensitive and 98% specific for the detection of clinical CMV infection in transplant recipients and 100% sensitive and 86% specific in persons with AIDS. Overall, CMV antigenemia was a more rapid and sensitive method for the detection of clinical CMV infection than either shell vial culture or conventional tube culture of blood.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Efficient generation of human anti-cytomegalovirus IgG monoclonal antibodies from preselected antigen-specific B cells.

Human anti-cytomegalovirus (CMV) specific B cells were enriched to a purity of up to 38% on CMV-coated dishes and subsequently clonally expanded in the presence of human T cell supernatant and irradiated murine thymoma helper cells. The expanded cells were immortalized by a mini-electrofusion with K6H6B5 myeloma cells. Twenty-two anti-CMV positive B cell clones could be obtained from as little as 1.5 ml donor blood. The majority of these clones produced anti-CMV antibodies of the IgG class. Ten anti-CMV positive B cell clones were submitted to separate mini-electrofusions yielding stable, human anti-CMV IgG-producing hybridomas in six out of ten fusions. These antibodies recognized different proteins of the CMV virus, as deduced from the immunofluorescence staining pattern on infected human fibroblasts.

Antibodies, Monoclonal↗
PubMed1992

Direct visualisation and quantification of cellular cytotoxicity using two colour flourescence.

A fluorescence method is described for the evaluation of cell death induced by cellular cytolytic activity. A green fluorescent membrane dye, D275, was used to label various target cell lines and propidium iodide (PI) uptake was used to assay cell death. Natural killer (NK), lymphokine activated killer (LAK) as well as targeted T cell mediated cellular cytotoxicity were quantified using the fluorescence method and compared to results obtained with the 51chromium (51Cr) release assay. A good correlation was found after an assay period of 4-8 h indicating that the fluorescence method is a reliable alternative to the 51Cr release assay.

Carbocyanines↗
PubMed1992

Increased production of antigen-specific B lymphocytes during in vitro immunization using carrier-specific T helper hybridomas.

An in vitro method to increase the production of hapten-specific antibody-forming B cells (AFC) using a carrier-specific T helper hybridoma and murine splenocytes is described. Naive splenocytes (6 x 10(6)/ml) are cultured in vitro in the presence of a hapten-carrier conjugate (DNP.OVA) and OVA-specific T helper hybridomas (0.5 x 10(6)/ml). After 4-5 days in vitro immunization (IVI), the maximum number of DNP-specific AFC were found using a spot-ELISA with twice the number of IgM positive cells as IgG positive AFC. The presence of antigen in the form of a hapten-carrier complex and the use of a carrier-specific Th hybridoma resulted in more hapten-specific AFC than when neither antigen nor Th hybridoma were present or when antigen alone or T help alone were used. Also when the hapten was conjugated to a carrier not recognised by the carrier-specific Th hybridoma there were considerably fewer (less than 50%) hapten specific AFC formed. When in vivo primed splenocytes (DNP) were boosted in vitro (IVB) under the same conditions as for IVI most hapten-specific AFC were found on day 4 and both anti-DNP IgM and IgG AFC were increased relative to IVI. Again most AFC were found when hapten was bound to the relevant carrier. In conclusion, carrier-specific T hybridomas can be used in an in vitro immunization procedure with naive or primed splenocytes to increase the frequency of anti-hapten AFC. This method offers an improvement over the current in vitro immunization procedures for the production of monoclonal antibodies.

Animals↗
PubMed1992

Dextran-magnetite particles: contrast-enhanced MRI of blood-brain barrier disruption in a rat model.

Dextran-magnetite particles (DMP) were studied for their use as a MR contrast agent to visualize lesions with a blood-brain barrier (bbb) disruption. A freezing injury to the rat cerebral cortex was used as a model of bbb disruption. The biodistribution of iv-injected DMP was studied using atomic absorption spectrophotometry, electron microscopy, and MRI. One hour after injection, focal accumulation of the particles in capillary endothelial cells could be demonstrated in the freezing lesion. Despite the observation that the relaxivity of DMP in vivo appears to be less well pronounced than that in vitro, the MR imaging studies show that DMP can be used to visualize bbb disruption with adequate contrast.

Animals↗