Biomedical subjects

C Ropke

Publications and source records attributed to C Ropke.

14 recordsLinked to original sources

PubMed2004

In vivo activation of STAT3 in cutaneous T-cell lymphoma. Evidence for an antiapoptotic function of STAT3.

A characteristic feature of neoplastic transformation is a perpetual activation of oncogenic proteins. Here, we studied signal transducers and activators of transcription (STAT) in patients with mycosis fungoides (MF)/cutaneous T-cell lymphoma (CTCL). Malignant lymphocytes in dermal infiltrates of CTCL tumors showed frequent and intense nuclear staining with anti-PY-STAT3 antibody, indicating a constitutive activation of STAT3 in vivo in tumor stages. In contrast, only sporadic and faint staining was observed in indolent lesions of patch and plaque stages of MF. Moreover, neoplastic lymphocytes in the epidermal Pautrier abscesses associated with early stages of MF did not express activated STAT3. To address the role of STAT3 in survival/apoptosis, CTCL tumor cells from an advanced skin tumor were transfected with either wild-type STAT3 (STAT3wt) or dominant-negative STAT3 (STAT3D). Forced inducible expression of STAT3D triggered a significant increase in tumor cells undergoing apoptosis, whereas forced expression of STAT3wt or empty vector had no effect. In conclusion, a profound in vivo activation of STAT3 is observed in MF tumors but not in the early stages of MF. Moreover, STAT3 protects tumor cells from apoptosis in vitro. Taken together, these findings suggest that STAT3 is a malignancy factor in CTCL.

Adult↗

PubMed2000

Dipeptidyl peptidase IV inhibition enhances the intestinotrophic effect of glucagon-like peptide-2 in rats and mice.

Glucagon-like peptide-2 (GLP-2) induces intestinal growth in mice; but in normal rats, it seems less potent, possibly because of degradation of GLP-2 by the enzyme dipeptidyl peptidase IV (DPP-IV). The purpose of this study was to investigate the survival and effect of GLP-2 in rats and mice after s.c. injection of GLP-2 with or without the specific DPP-IV inhibitor, valine-pyrrolidide (VP). Rats were injected s.c. with 40 microg GLP-2 or 40 microg GLP-2+15 mg VP. Plasma was collected at different time points and analyzed, by RIA, for intact GLP-2. Rats were treated for 14 days with: saline; 15 mg VP; 40 microg GLP-2, 40 microg GLP-2+15 mg VP; 40 microg GLP-2 (3-33). Mice were treated for 10 days with: saline; 5 microg GLP-2; 5 microg GLP-2+1.5 mg VP; 25 microg GLP-2; 25 microg GLP-2 (3-33). In both cases, body weight, intestinal weight, length, and morphometric data were measured. After s.c. injection, the plasma concentration of GLP-2 reached a maximum after 15 min, and elevated concentrations persisted for 4-8 h. With VP, the concentration of intact GLP-2 was about 2-fold higher for at least the initial 60 min. Rats treated with GLP-2+VP had increased (P < 0.01) small-bowel weight (4.68 +/- 0.11%, relative to body weight), compared with the two control groups, [3.01 +/- 0.06% (VP) and 2.94 +/- 0.07% (NaCl)] and GLP-2 alone (3.52 +/- 0.10%). In mice, the growth effect of 5 microg GLP-2+VP was comparable with that of 25 microg GLP-2. GLP-2 (3-33) had no effect in rats, but it had a weak effect on intestinal growth in mice. The extensive GLP-2 degradation in rats can be reduced by VP, and DPP-IV inhibition markedly enhances the intestinotrophic effect of GLP-2 in both rats and mice. We propose that DPP-IV inhibition may be considered to enhance the efficacy of GLP-2 as a therapeutic agent.

Animals↗

PubMed1993

Regulatory effects in vitro by thymic medullary epithelial cells on TCR transgenic T cells specific for male H-Y antigens.

To evaluate the ability of thymic epithelial cells (TEC) to influence growth and differentiation of antigen specific T cells, we have used female transgenic (TG) mice expressing a receptor on the majority of their T cells for the male (H-Y) antigen in the context of H-2Db antigens. Male or female TEC expanded in serum-free medium were co-cultured with female TG thymocytes. FAC-Scan analysis after 3 days of co-culture did not indicate any selective deletion of subpopulations induced by male TEC. In contrast, the presence of TEC in TG thymocyte cultures led to increased proliferation, irrespective of the type of TEC and stimulus used. Limiting dilution (LD) proliferation analyses, using irradiated male spleen cells as stimulator cells, showed increased clonability of CD4-CD8+ cells, but reduced clonability of CD4-CD8- thymocytes, in the presence of both male and female TEC. Clones from the LD cultures were expanded for several weeks. Expanded clones all expressed the v beta 8.2+ TG TCR. One-half of the expanded TG CD8+ T cell clones obtained from LD cultures exhibited H-Y specific proliferation, and the majority of clones showed antigen-specific IL-3 secretion. Expanded clones did not develop into a cytotoxic machinery in the present culture system.

Animals↗

PubMed1992

Human thymic epithelial cells in serum-free culture: nature and effects on thymocyte cell lines.

Thymic epithelial cells (TEC) have been cultured for several months and/or for 4 to 5 transfers in a growth factor-defined serum-free medium without concurrent growth of other cell types. The use of monoclonal antibodies and alpha MAM-6 indicated that the majority of TEC were of medullary origin. The vast majority of cells were positive for LFA-3 and class I, and class II expression was low or absent. Supernatants from the cultures were shown to contain IL-1 beta, IL-6, and M-CSF. Coculture of cloned subpopulations of thymocytes and TEC showed effects of TEC and of secreted ILs on thymocyte proliferation. High percentages of TEC were able to bind DN, DP, or SP thymocyte populations, partly via CD2-LFA-3 adhesion. Thus, it is possible to culture TEC without unknown serum factors and with maintenance of functional activities.

Antibodies, Monoclonal↗

PubMed1992

T-cell colony formation from murine thymocyte subpopulations and pre-T cells.

Murine thymocytes are able to proliferate on clonal basis as colonies in the semisolid medium methylcellulose. It has previously been shown that the colony-forming cells are predominantly rather mature thymocytes and presumably exclusively single positive CD8+ cells. The results of the present study point to that also immature CD4-CD8- (DN = double negative) thymocytes and pre-T cells from nude mice are able to form colonies in methylcellulose culture. The numbers of colonies are increased by the presence of phorbolester, and it is shown by the addition of various interleukins to the culture that IL-2 is the essential interleukin in colony formation. It is further shown that all colony cells derived from DN thymocytes are of the CD4-CD8+ phenotype, while nude mouse precursors give rise to either CD8+ or DN colony cells. Thus, no CD4+ T cells were able to proliferate as colonies by the present culture method, even after exposure to a number of different interleukins or phorbolesters. This makes the method a reliable tool for clonal growth of both immature and mature CD8+ thymocytes and T cells.

Animals↗

PubMed1990

Short-term cultivation of murine thymic epithelial cells in a serum-free medium.

Thymic epithelial cells were grown in defined medium without unknown serum factors and without concurrent growth of other cell types. Thymic tissue was obtained from 1- to 4-wk-old mice, disaggregated, and incubated in a mixture of collagenase-dispase-DNAse. The resulting organoids were seeded on collagen-coated flasks. The culture medium consisted of DME-F12 with low or high concentration of Ca2+ supplemented with insulin, epidermal growth factor, cholera toxin, hydrocortisone, and transferrin. Under these conditions, explants attached to the substrate within 2 d, and expanding epithelioid monolayer islets emerged from the organoids during the following days. [3H]Thymidine incorporation revealed a growth fraction of the cells close to 5%. By omitting either epidermal growth factor, insulin, or cholera toxin from the medium, pronounced reduction in sizes of islets and in [3H]thymidine incorporation was found. Throughout the culture period, the islets appeared as continuous sheets of polygonal cells. The epithelial nature of the expanding cell islets was confirmed by demonstration of cytokeratins and of desmosomes. Ultrastructural evaluation of early cultures revealed clusters of epithelial cells intermixed with lymphocytes, and late cultures showed a typical pattern of stratified keratinizing epithelium. However, squamous metaplasia was avoided by the use of low Ca2+ medium, which also proved essential for cell transfer. MHC class II antigen was detected on the majority of the cultured cells, and culture supernatants contained co-mitogenic activity for thymocytes and GM-colony stimulating activity.

Animals↗

PubMed1990

Renewal rates of murine T-lymphocyte subsets.

The proliferative dynamics of T-cell subsets in lymphoid organs of BALB/c mice have been evaluated by means of [3H]thymidine injections for up to 3 days, followed by FACS and autoradiography. In the thymus, cells positive for both CD4 and CD8 antigens were more rapidly renewed than single-positive cells. Cell populations showing strong expression of Thy-1 and weak expression of CD5 antigens were more rapidly renewed than populations with the opposite antigen expressions. The results obtained from the spleen and the lymph nodes indicated that the majority of T cells have life spans exceeding a few days, and comparable cell kinetics were found in the different T-cell subpopulations. Results obtained after injections of hydroxyurea, which causes elimination of cycling cells, paralleled the autoradiographic results.

Animals↗

PubMed1990

Thymic epithelial cells. I. Expression of strong suppressive (veto) activity in mouse thymic epithelial cell cultures.

We show that thymic epithelial cells grown under serum-free conditions in a chemically defined culture medium can act as veto cells in vitro. The veto activity of thymic epithelial cells results in inactivation of specific alloreactive cytotoxic T-cell precursors at the clonal level. It is concluded that the epithelial stromal cells of the thymus, by acting as veto cells, may be responsible for the negative intrathymic selection of self-reactive thymocytes leading to elimination of the vast majority of immature thymic lymphocytes.

Animals↗

PubMed1988

Suppression of the number of clonally expanding T cells by CD8+ cells as demonstrated by murine T-cell colony formation.

Clonally developing murine T cells in the form of T-cell colonies (TCC) in methylcellulose were used to investigate the interaction between polyclonally activated T cells. Only CD8+ T cells proliferate in the methylcellulose and form TCC after stimulation with PHA and IL-2. When the number of developing TCC was counted as a measure of developing clones, it was found that increased cell numbers in the cultures led to decreased percentages of TCC (Number of TCC per 100 seeded cells). This was found already at very low cell concentrations: 40 cells per ml culture, and was maintained at least up to 10,000 cells per culture. Cell sorting (FACS) of cells showed that the suppression of developing clones was mediated via a non-adherent, Thy-1+, CD8+ cell, present in lymph nodes, spleen and the thymic medulla. Such seemingly non-specific suppressor cells may be considered in the network regulation of the functionally mature T-cell population.

Animals↗

PubMed1974