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Biomedical subjects

R Schmits

Publications and source records attributed to R Schmits.

At least 19 recordsLinked to original sources
PubMed2006

The cervical lymph node preparation: a novel approach to study lymphocyte homing by intravital microscopy.

OBJECTIVE: Lymphocyte recirculation constitutes an integral part of the adaptive immune system. Blood-borne lymphocytes migrate into secondary lymphoid organs, crossing the vascular wall of site-specific high endothelial venules (HEVs). We created a preparation of the cervical lymph node in mice to study lymphocyte homing in vivo. METHODS AND RESULTS: Our novel approach allowed the detailed analysis of hemodynamics and lymphocyte-HEV endothelium interactions by means of intravital fluorescence microscopy. We confirm the key roles of L-selectin and LFA-1 for lymphocyte homing. Blockade of L-selectin function inhibited lymphocyte rolling and firm adhesion by 92% and 66%. In LFA-1-deficient mice, lymphocyte firm adhesion was reduced by 70%. In addition to the microcirculation studies, the cervical lymph node preparation allowed for visualization of afferent lymphatic transport, which is mainly derived from the oral mucosa. CONCLUSION: This study reports a novel technical tool for the detailed in vivo analysis of adaptive immune responses.

Animals↗
PubMed2003

Practicability and acute haematological toxicity of 2- and 3-weekly CHOP and CHOEP chemotherapy for aggressive non-Hodgkin's lymphoma: results from the NHL-B trial of the German High-Grade Non-Hodgkin's Lymphoma Study Group (DSHNHL).

BACKGROUND: There is evidence that intensified variants of the classical 3-weekly CHOP-21 chemotherapy [cyclophosphamide (C), doxorubicin (H), vincristine (O), prednisone (P)] may improve treatment outcome in aggressive lymphoma. Three variants using either an addition of etoposide (CHOEP-21: 100 mg/m(2) on days 1-3), the shortening to 2-week intervals using recombinant human granulocyte colony-stimulating factor (rhG-CSF; CHOP-14) or both (CHOEP-14) are currently compared with CHOP-21 in the NHL-B trial of the German High-Grade Non-Hodgkin's Lymphoma Study Group (DSHNHL). To enable more extensive testing of these schemes we here characterise their practicability regarding schedule adherence, acute haematotoxicity and need for supportive treatment. PATIENTS AND METHODS: The trial included patients with normal lactate dehydrogenase (LDH) aged </=60 years (NHL-B1) and patients aged 61-75 years (NHL-B2). The data are taken from an interim analysis. Data from 959 patients (CHOP-21: 232; CHOP-14: 238; CHOEP-21: 244; CHOEP-14: 245) from 162 institutions with a total of 5331 therapy cycles were evaluated. RESULTS: The dose adherence in the NHL-B1 trial was excellent. The median relative dose (RD; i.e. actually given compared to planned dose) exceeds 98% for the myelosuppressive drugs in all four regimens. Only </=5% of patients received a relative dose <80% (RD <80). The median treatment duration could be shortened as scheduled for both CHOP-14 by 36 days and CHOEP-14 by 35 days. The dose adherence in the NHL-B2 trial was excellent for CHOP-21 and CHOP-14 for the myelosuppressive drugs (median RD >/=98%, RD <80 </=15%). Addition of etoposide, however, was accompanied by more dose erosion (median RD >/=97%, RD <80 </=17% for CHOEP-21 and </=27% for CHOEP-14). The median treatment duration could be shortened by 34 days with CHOP-14 compared with CHOP-21. Less treatment shortening was feasible for CHOEP-14 compared with CHOP-21 (median of 29 days). CHOP-14 and CHOP-21 were similar regarding toxicity profile, rate of infection, use of antibiotics, rate of transfusions and hospitalisation. CHOEP schemes were associated with a higher rate of infections, more transfusion requirements, more antibiotic use and longer hospitalisation than the CHOP schemes, particularly in patients aged >60 years. Haematopoietic recovery was age- and treatment-related. CONCLUSIONS: CHOP-14 with the addition of rhG-CSF is safe and practicable in a large multicentre setting in patients aged 18-75 years. Despite shorter treatment intervals it can be delivered at the same dose as the classical 3-weekly CHOP with a comparable toxicity profile. The addition of etoposide is feasible and safe for patients </=60 years old in both the CHOEP-21 and CHOEP-14 schemes. For patients >60 years of age the addition of etoposide is associated with marked dose erosion due to increased toxicity. In this age group CHOEP should be used with caution.

Acute Disease↗
PubMed2002

Analysis of the B cell repertoire against autoantigens in patients with giant cell arteritis and polymyalgia rheumatica.

The analysis of the antibody repertoire of patients with giant cell arteritis (GCA) and polymyalgia rheumatica (PMR) might identify target antigens of the autoimmune response with potential relevance to our understanding of the pathogenesis of the disease and to the development of serodiagnostic tests. To detect such antigens, we screened a cDNA library derived from normal human testis for antigens reacting with IgG antibodies in the 1 : 250 diluted sera of three patients with untreated GCA using SEREX, the serological identification of antigens by recombinant cDNA expression cloning. Of 100 000 clones screened with each serum, six, 28 and six clones, respectively, were positive, representing a total of 33 different antigens. Most of the antigens reacted only with the serum used for identification and/or at a similar frequency with normal control sera. However, lamin C and the nuclear antigen of 14 kD reacted specifically with 32% of GCA/PMR, but with none of the control sera, while human cytokeratin 15, mitochondrial cytochrome oxidase subunit II, and a new gene product were detected preferentially, but not exclusively by sera from GCA/PMR patients. We conclude that patients with GCA/PMR develop antibodies against a broad spectrum of human autoantigens. Antibodies against human lamin C, the nuclear autoantigen of 14 kD as well as human cytokeratin 15, mitochondrial cytochrome oxidase subunit II and the product of a new gene should be investigated further to determine their value as tools for the diagnosis and/or the definition of clinical subgroups of patients with GCA/PMR.

Adult↗
PubMed2001

Systematic search and molecular characterization of the antigenic targets of myeloma immunoglobulins: a monoclonal IgA from a female patient targeting sperm-specific cylicin II.

The identification of the antigenic stimuli of B-cell neoplasms might be of considerable importance since a causal relationship between these neoplasms and antigenic stimulation has been suggested. To date the identification of such antigens has been erratic and accidental. For a systematic search and molecular characterization of human proteins that are antigenic target structures of myeloma-associated immunoglobulins, we applied SEREX (serological analysis of antigens by recombinant cDNA expression cloning) using a testis cDNA expression library and myeloma proteins from 42 patients. A monoclonal IgA from a female patient was shown to target sperm-specific cylicin II. The specificity of the reaction was confirmed by the characteristic staining of the equatorial belt of human sperm heads by the patient's myeloma protein. Serological analysis of recombinantly expressed cDNAs is a straightforward and high throughput approach for the molecular characterization of the targets of myeloma-associated immunoglobulins. The analysis of the antigenic spectrum of immunoglobulins associated with B-cell neoplasms will provide valuable information for the understanding of the pathogenesis of these diseases.

Aged↗
PubMed2001

Lack of in vivo function of CD31 in vascular thrombosis.

A murine model of endothelial cell injury-based vascular thrombosis was used to test the role of platelet-endothelial cell adhesion molecule-1 (PECAM-1, CD31) in blood cell aggregate formation and vessel occlusion in vivo. Photochemically-induced thrombus formation was analyzed in detail using intravital fluorescence microscopy of individual microvessels in cremaster muscle preparations of CD31-deficient and wildtype mice. In venules, epi-illumination induced rapid thrombus formation with first platelet deposition after 0.56 +/- 0.11 min and complete vessel occlusion within 5.05 +/- 0.45 min. In arterioles, thrombus formation was markedly delayed with first platelet deposition after 3.03 +/- 0.47 min and complete vessel occlusion within 10.04 +/- 1.26 min. Kinetics of thrombus formation in both venules (first platelet deposition: 0.52 +/- 0.1 min; vessel occlusion: 5.03 +/- 0.52 min) and arterioles (first platelet deposition: 3.06 +/- 0.68 min; vessel occlusion: 10.02 +/- 1.38 min) of CD31-deficient mice was found almost identical compared with that in wildtype animals. Tail bleeding time was 233 +/- 24 s in wildtype and 243 +/- 32 s in CD31-deficient mice. Moreover, CD31-deficient and wildtype mice revealed comparable interaction of leukocytes to endothelium. This study shows for the first time in vivo that CD31 is not critically involved in blood cell thrombus formation upon endothelial cell injury.

Animals↗
PubMed2000

Cutting edge: contribution of NK cells to the homing of thymic CD4+NKT cells to the liver.

In contrast to peripheral lymphoid organs, in the liver a high proportion of T cells are CD4+NKT cells. We have previously reported that LFA-1 plays a pivotal role in the homing of thymic CD4+NKT cells to the liver. In the present study, we further assessed which cell type participates in the homing of thymic CD4+NKT cells to the liver. The accumulation of donor thymocyte-derived CD4+NKT cells in the liver of SCID mice that had been reconstituted with thymocytes from C57BL/6 mice was severely impaired by in vivo depletion of NK cells, but not Kupffer cells in recipients. These results suggest that NK cells participate in the homing of thymic CD4+NKT cells to the liver. We assume that LFA-1 expressed on NK cells is involved in this mechanism.

Animals↗
PubMed2000

Participation of leukocyte function-associated antigen-1 and NK cells in the homing of thymic CD8+NKT cells to the liver.

A distinct CD8+NKT cell population expressing TCRalpha/beta or TCRgamma/delta has been identified in liver and thymus. We wondered whether cell adhesion molecules play a role in the homing of CD8+NKT cells to the liver. The number of liver CD8+NKT cells was markedly reduced in leukocyte function-associated antigen (LFA)-1-/- mice compared with wild-type (WT) mice. The reduction was restricted to the liver only and no measurable alterations were found in other organs. In the liver of SCID mice reconstituted with thymocytes from LFA-1-/- or WT mice, the number of donor-derived CD8+NKT cells was comparable and the vast majority of these cells expressed TCRalpha/beta. In a reciprocal radiation thymocyte reconstitution system with LFA-1-/- and WT mice, LFA-1 expressed on liver cells other than CD8+NKT cells appeared to be required for the homing of thymic CD8+NKT cells to the liver. The accumulation of donor thymocyte-derived CD8+NKT cells in the liver of SCID mice was severely impaired by in vivo depletion of NK cells, but not of Kupffer cells. These results not only indicate that thymus provides a source for CD8+NKT cells expressing TCRalpha/beta in the liver, but also suggest that LFA-1 expressed on NK cells is involved in the homing of thymic CD8+NKT cells to the liver.

Animals↗
PubMed2000

Gene-modified spontaneous Epstein-Barr virus-transformed lymphoblastoid cell lines as autologous cancer vaccines: mutated p21 ras oncogene as a model.

The transfer of genes coding for tumor antigens (Ags) into Ag-presenting cells is a promising strategy to develop cancer vaccines for patients not limited by major histocompatibility complex restriction. To test whether autologous lymphoblastoid cell lines (LCL) can be used as an alternative to dendritic cells for Ag presentation, we established LCL by spontaneous growth in cyclosporin-containing medium in vitro (SP-LCL). SP-LCL, which have an advantage over B95-8-transfected LCL in that they carry no risk of introducing a new infectious agent when used for vaccination, served as a permanent source for transfection with an episomal Epstein-Barr virus-based expression vector encoding the Ki-ras p21 oncogene carrying a point mutation at codon 12 (muRas) as a model tumor Ag. The ability of muRas-transfected SP-LCL (muRas-LCL) to induce immunoreactivity was determined in vitro. After electroporation with an optimized protocol, muRas-LCL expressed mutated ras peptides for a considerable period of time (at least 8 weeks) on the cell surface. The transfection procedure did not affect the expression of the costimulatory molecules B7.1, intercellular adhesion molecule-1, and leukocyte function associated Ag-3 by SP-LCL. muRas-LCL were able to induce muRas-specific cytotoxic T lymphocytes from three of three healthy donors and one of one patient with pancreatic carcinoma. Our results suggest that the gene transfer of muRas sequences to SP-LCL leads to an endogenous processing of this Ag in the major histocompatibility complex class I pathway and to functional presentation of antigenic peptides to CD8+ T lymphocytes. Autologous SP-LCL can serve as an unlimited renewable source for autologous cellular vaccines and appear to be good candidates as presenters for a wide range of human tumor Ags.

B7-1 Antigen↗
PubMed2000

Lymphocyte function antigen 1 (LFA-1) mediates early tumour necrosis factor alpha-induced leucocyte adhesion in venules.

A co-ordinated expression of specific adhesion molecules regulates leucocyte-endothelium interactions in the microcirculation. In the present study, we used intravital microscopy of the cremaster muscle in CD11a gene-targeted mice to examine the role of lymphocyte function antigen 1 (LFA-1, CD11a/CD18) in tumour necrosis factor alpha (TNF-alpha)-induced leucocyte rolling and firm adhesion in venules. We found that 30 min after TNF-alpha administration leucocyte rolling was unchanged compared with phosphate-buffered saline (PBS)-treated mice and similar in LFA-1-deficient and wild-type animals. In contrast, firm leucocyte adhesion in venules increased by almost 10-fold following 30 min of TNF-alpha challenge in LFA-1-expressing animals, whereas no increase was observed in LFA-1-deficient mice. Four hours after intrascrotal administration of TNF-alpha, venular leucocyte adhesion was found to be markedly increased, but similar in extent to LFA-1-deficient and wild-type mice. Histological examination of haematoxylin-eosin-stained tissue sections revealed that approximately 90% of the leucocytes in the TNF-alpha-stimulated venules in both wild-type and LFA-1-deficient mice were polymorphonuclear. Taken together, our functional in vivo data demonstrate that LFA-1 is an important adhesion molecule in early TNF-alpha-induced venular leucocyte adhesion.

Animals↗
PubMed1999

Evidence for the involvement of CD44 in endothelial cell injury and induction of vascular leak syndrome by IL-2.

At sites of chronic inflammation seen during infections, autoimmunity, graft-vs-host response, and cytokine therapy, endothelial cell injury is known to occur, the exact mechanism of which is unknown. In the current study we used IL-2-induced vascular leak syndrome (VLS) as a model to investigate whether cytotoxic lymphocytes use CD44 in mediating endothelial cell injury. Administration of IL-2 to wild-type mice triggered significant VLS in the lungs and liver. In contrast, in CD44 knockout (KO) mice, IL-2-induced VLS was markedly reduced in the lungs and liver. IL-2-treated wild-type and CD44 KO mice had similar levels of perivascular infiltration with lymphocytes in the lungs and liver. This suggested that the decrease in VLS seen in CD44 KO mice was not due to the inability of lymphocytes to migrate to these organs. Ultrastructural studies demonstrated extensive endothelial cell damage in the lungs and liver of IL-2-treated wild-type, but not CD44 KO, mice. Moreover, CD44-KO mice exhibited a marked decrease in IL-2-induced lymphokine-activated killer cell activity. The induction of VLS was dependent on the expression of CD44 on immune cells rather than endothelial cells because adoptive transfer of CD44+, but not CD44- spleen cells along with IL-2 into CD44 KO mice triggered VLS. The IL-2-induced VLS was blocked by administration of F(ab')2 of Abs against CD44. The current study demonstrates that CD44 plays a key role in endothelial cell injury. Blocking CD44 in vivo may offer a novel therapeutic approach to prevent endothelial cell injury by cytotoxic lymphocytes in a variety of clinical disease models.

Adoptive Transfer↗
PubMed1999

Critical role of leukocyte function-associated antigen-1 in liver accumulation of CD4+NKT cells.

In contrast to peripheral lymphoid organs, a high percentage of T cells in the liver are CD4+NKT cells. We asked whether adhesion molecules play any role in the accumulation of CD4+NKT cells in the liver. Liver CD4+NKT cells expressed ICAM-1 and high levels of LFA-1. In the livers of LFA-1-deficient mice, the number of CD4+NKT cells was markedly decreased. This reduction was restricted to the liver, and no reduction was found in the other organs analyzed. In contrast, the number of liver CD4+NKT cells in ICAM-1-deficient mice was only marginally reduced. In a reciprocal radiation thymocyte reconstitution system with LFA-1-deficient and wild-type mice, LFA-1 expressed on liver cells other than CD4+NKT cells was required for an accumulation of CD4+NKT cells in the liver. These results demonstrate a crucial role for LFA-1 in the accumulation of CD4+NKT cells in the liver.

Adoptive Transfer↗
PubMed1998

Cooperation between CD44 and LFA-1/CD11a adhesion receptors in lymphokine-activated killer cell cytotoxicity.

IL-2-activated NK cells exhibit cytotoxic activity against a wide variety of tumor cells in a non-MHC-restricted fashion and in the absence of prior sensitization. The molecular mechanisms that regulate the cytotoxicity and attachment of activated killer cells to tumor target cells are not known. We provide genetic evidence in CD44(-/-) and LFA-1(-/-) mice that the cell adhesion receptors LFA-1 and CD44 regulate the cytotoxic activity of IL-2-activated NK cells against a variety of different tumor cells. This defect in cytotoxicity was significantly enhanced in mice that carried a double mutation of both CD44 and LFA-1. In vitro differentiation, TNF-alpha and IFN-gamma production, and expression of the cytolytic effector molecules perforin and Fas-L were comparable among IL-2-activated NK cells from LFA-1(-/-), CD44(-/-), CD44(-/-)LFA-1(-/-), and control mice. However, CD44(-/-), LFA-1(-/-), and CD44(-/-)LFA-1(-/-) IL-2-activated NK cells showed impaired binding and conjugate formation with target cells. We also show that hyaluronic acid is the principal ligand on tumor cells for CD44-mediated cytotoxicity of IL-2-activated NK cells. These results provide the first genetic evidence of the role of adhesion receptors in IL-2-activated NK killing. These data also indicate that distinct adhesion receptors cooperate to mediate binding between effector and target cells required for the initiation of "natural" cytotoxicity.

Animals↗
PubMed1998

Transendothelial migration and trafficking of leukocytes in LFA-1-deficient mice.

The leukocyte integrin LFA-1 plays an important role in leukocyte trafficking and the immune response. Using LFA-1-deficient mice, we demonstrate that LFA-1 regulates the trafficking of lymphocytes to peripheral lymph nodes, and, to a lesser degree, to mesenteric lymph nodes and acute inflammatory sites. LFA-1, either because of its role in initial adhesion and/ or the passage of leukocytes across endothelial cells, plays a vital role in T lymphocyte and neutrophil transendothelial migration. Neutrophils and activated T lymphocytes from LFA-1-deficient mice were unable to cross endothelial cell monolayers in response to a chemokine gradient, whereas wild-type (WT) T lymphocytes and neutrophils were capable of migration. By contrast, LFA-1-deficient T lymphocytes displayed normal chemotaxis to the same chemokine. Our studies with LFA-1-deficient monocytes indicate that LFA-1 acts in concert with complement receptor 3 to mediate transendothelial migration of these cells, as anti-CD18 monoclonal antibodies (mAb) blocked both WT and LFA-1-deficient monocyte transendothelial migration, whereas anti-CD11 b mAb preferentially blocked transendothelial migration of LFA-1-deficient monocytes. Finally, whereas anti-CD31 mAb blocked WT monocyte and neutrophil transendothelial cell migration they did not block LFA-1-deficient monocyte and neutrophil transendothelial migration.

Animals↗
PubMed1997

CD44 regulates hematopoietic progenitor distribution, granuloma formation, and tumorigenicity.

CD44 is expressed in various isoforms on numerous cell types and tissues during embryogenesis and in the mature organism. CD44 may also be involved in tumor growth. To study the multiple roles of CD44, we abolished expression of all known isoforms of CD44 in mice by targeting exons encoding the invariant N-terminus region of the molecule. Surprisingly, mice were born in Mendelian ratio without any obvious developmental or neurological deficits. Hematological impairment was evidenced by altered tissue distribution of myeloid progenitors with increased levels of colony-forming unit-granulocyte-macrophage (CFU-GM) in bone marrow and reduced numbers of CFU-GM in spleen. Fetal liver colony-forming unit-spleen and granulocyte colony-stimulating factor mobilization assays, together with reduced CFU-GM in peripheral blood, suggested that progenitor egress from bone marrow was defective. In what was either a compensatory response to CD44 deficiency or an immunoregulatory defect, mice also developed exaggerated granuloma responses to Cryotosporidium parvum infection. Finally, tumor studies showed that SV40-transformed CD44-deficient fibroblasts were highly tumorigenic in nude mice, whereas reintroduction of CD44s expression into these fibroblasts resulted in a dramatic inhibition of tumor growth.

Alternative Splicing↗
PubMed1997

Distinct roles for LFA-1 and CD28 during activation of naive T cells: adhesion versus costimulation.

Efficient T cell activation requires the engagement of a variety of ligand/receptor molecules in addition to T cell receptor (TCR)-major histocompatibility complex (MHC)/peptide interactions. The leukocyte function antigen 1 (LFA-1) and the CD28 glycoprotein have both been implicated in T cell activation. The present study dissects the roles of LFA-1 and CD28 in the activation of naive virus-specific CD8+ T cells. We demonstrate that LFA-1 facilitates T cell activation by lowering the amounts of antigen necessary for T cell activation. In the absence of LFA-1, 100-fold more antigen was required for T cell-antigen-presenting cell (APC) conjugation and all subsequent events of T cell activation, including TCR down-regulation, Ca2+-flux, T cell proliferation, and lytic effector cell induction. Thus, LFA-1 facilitates the functional triggering of TCRs by promoting adhesion of T cells to APCs but does not affect T cell activation otherwise. In contrast, CD28 played an entirely different role during T cell activation. CD28 reduced the number of TCRs that had to be triggered for T cell activation and allowed activation of T cells by low affinity ligands. CD28 but not LFA-1 prevented induction of T cell unresponsiveness after stimulation of TCRs. These results demonstrate that LFA-1 and CD28 exhibit distinct, nonoverlapping ways to influence T cell activation and suggest that the terms costimulation and signal 2 should be revisited.

Animals↗