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Biomedical subjects

W Müller-Ruchholtz

Publications and source records attributed to W Müller-Ruchholtz.

At least 55 records · Page 3Linked to original sources
PubMed1994

Human monoclonal antibodies recognize early and late viral proteins of human cytomegalovirus.

Human monoclonal antibodies directed against human cytomegalovirus were generated by fusion of in vitro stimulated human spleen lymphocytes from an HCMV-seropositive 53-year-old organ donor with the mouse myeloma cell line Ag8.653. Fourteen human/mouse hybridomas producing anti-cytomegalovirus IgG were screened by an ELISA technique and four selected clones have been established since March 1988, generating about 5-40 micrograms/24 h IgG per ml culture supernatant. Reference and local cytomegalovirus strains were stained by the antibodies without showing cross-reactivity to other herpes viruses. Three monoclonal antibodies, A4B4 (IgG11), A6B3 (IgG1k) and A6A2 (IgG1k), immunoprecipitated a 68 kDa early viral protein which appears during the infectious cycle, first in the nucleus (18-24 h) and then also in the cytoplasm (24-96 h) of infected cells. Inhibition of DNA replication restricted the detection of the 68 kDa viral protein to the nucleus of infected cells. Staining of unfixed infected cells showed that two of the antibodies bound at the surface of a few cells. The fourth monoclonal antibody A3C5 (IgG11) immunoprecipitated a 34/38 kDa late viral protein which appears in the nucleus (48-72 h) of infected cells. These antibodies enable us to study the human host response to human cytomegalovirus and to elucidate the functions of human antibodies especially in their interaction with the T-cell response.

Animals↗
PubMed1993

Effective mobilisation of peripheral blood progenitor cells with 'Dexa-BEAM' and G-CSF: timing of harvesting and composition of the leukapheresis product.

The mini-BEAM regimen (BCNU, etoposide, cytarabine, melphalan) and its modification 'Dexa-BEAM' are effective salvage protocols for relapsed Hodgkin's disease and non-Hodgkin's lymphoma. Since many patients with relapsed lymphoma are eligible for high-dose chemotherapy with autologous stem cell rescue, we were interested in the suitability of these second line regimens for mobilising peripheral blood progenitor cells (PBPC). The kinetics of PBPC were studied in 15 patients treated with Dexa-BEAM and granulocyte colony-stimulating factor (G-CSF). Leukocytes started to rise from < 0.5 nL-1 on day 18 (16-22) after Dexa-BEAM, and exceeded 10 nL-1 on day 20 (18-28). Peripheral blood CFU-GM peaked on day 21 (19-28) and declined slowly thereafter; the median leukocyte count was 18.7 nL-1 (12.2-60) on the day of CFU-GM-peak. The maximum number of CFU-GM circulating in peripheral blood was inversely correlated to the duration of leukopenia after Dexa-BEAM. Measurement of CD34+ cells with the monoclonal antibody 8G12-PE (HPCA-2) predicted the number of CFU-GM precisely in both peripheral blood and leukapheresis products (r = 0.90-0.95). Two to six leukapheresis procedures yielded 6.39 x 10(8) mononuclear cells kg-1 (1.82-13.49) containing 44.4 x 10(4) CFU-GM kg-1 (2.2-213.8). Immunophenotypical analysis revealed that the percentage of CD19+ B cells was very low in all collection products (less than 1%). Nine patients were autografted with PBPC (15.4-213.8 x 10(4) CFU-GM kg-1) after myeloablative chemotherapy and experienced rapid and sustained engraftment (Platelets > 50 nL-1 on day +13 [9-22]). We conclude that PBPC can be mobilised effectively by Dexa-BEAM plus G-CSF. An adequate timing of PBPC collection (when the leukocyte count has exceeded 10 nL-1) and evaluation of the progenitor content of the leukapheresis products with 8G12-PE will allow to minimise the number of leukaphereses.

Adult↗
PubMed1993

Granulocyte-colony-stimulating factor induces increased serum levels of soluble interleukin 2 receptors preceding engraftment in autologous bone marrow transplantation.

The serum levels of soluble interleukin 2 receptors (sIL-2R) were determined in 19 patients who received high-dose chemotherapy and an autologous or syngeneic bone marrow transplant (BMT) for treatment of Hodgkin's disease (n = 18) or non-Hodgkin's lymphoma (n = 1). Twelve patients received granulocyte colony-stimulating factor (G-CSF) from day 0 or day +1 after autologous BMT until the white blood cell count had been stable for 9 d above 1 x 10(9)/l, the remaining seven patients did not receive growth factors. In all G-CSF-treated patients the sIL-2R levels increased steadily in the early post-transplant course, even in the absence of infection. This increase was statistically significant 2-4 d prior to the appearance of leucocytes in the peripheral blood (median 340 pM versus median 256 pM immediately after BMT, P < 0.025) and peaked with the appearance of first peripheral blood leucocytes (median 536 pM, P < 0.001). Cessation of G-CSF administration resulted in a decline of sIL-2R levels. In contrast, five of seven patients without G-CSF treatment did not exhibit an sIL-2R increase before or at the time of engraftment. Infection was associated with a rise of sIL-2R levels. A correlation between sIL-2R levels and total leucocyte count, lymphocyte count, or CD25+ lymphocyte count was not evident. These data suggest that after autologous BMT G-CSF induces increased sIL-2R levels, which occur independent of lymphocyte activation. This may be compatible with involvement of immature bone marrow cells in G-CSF-induced sIL-2R release.

Adolescent↗
PubMed1993

Interaction of papain-digested HLA class I molecules with human alloreactive cytotoxic T lymphocytes (CTL).

Acute immunological rejection events of transplanted allogeneic organs are strongly dependent on T cell reactivity against foreign MHC products. The recognition requirements of alloreactive cytotoxic T cells are of particular interest for finding approaches to modulating alloreactivity. The role of the allogeneic MHC molecule itself and/or an associated peptide in the interaction with the T cell receptor is still, however, unclear. Our studies have focused on the interactions of papain-digested HLA class I molecules with alloreactive CD8+ CTL. These polypeptides, consisting of the polymorphic alpha 1 and alpha 2 and the monomorphic alpha 3 domains, were used in both soluble and immobilized form to study their functional effects on anti-HLA-A2 reactive CTL. Purified polypeptides were of molecular mass 32-34 kD. HLA-A2 polypeptides (0.55 micrograms/ml) in soluble form induced half-maximal reduction of CTL cytotoxicity. These concentrations were quantitatively comparable to the effective doses of intact HLA class I molecules, which contain the hydrophobic transmembrane domain and the intracytoplasmic tail. In addition, specific activation requirements of these CTL were investigated in a serine esterase release assay. Maximal degranulation was observed after 2 h of antigen contact. Purified HLA class I molecules allospecifically activated the anti-HLA-A2 CTL to degranulate serine esterase, when immobilized on plastic microtitre plates. Thus, polypeptides containing the polymorphic alpha 1 and alpha 2 domains of human class I molecules potentially modulate the cytotoxic T cell response. This might have implications for the reduction or prevention of allograft rejection in recipients of foreign organs.

Cytotoxicity, Immunologic↗
PubMed1993

Oncogene transformation can induce tolerogenicity in murine macrophages after down-regulation of immunogenicity without altering major histocompatibility complex antigen expression.

In vitro studies on cell lines may allow analyses of the mechanisms of immunogenicity and tolerogenicity in cells. We used a model of oncogenic transformation of an established murine macrophage cell line and report here that one v-mos-transformed clone expressing unaltered high amounts of MHC class I and II antigens does not induce proliferation of unprimed T cells in primary mixed lymphocyte reactions, in sharp contrast to its non-transformed parental cells. Interestingly, this clone induces specific unresponsiveness, as revealed by the lack of responsiveness of MHC-specific T cells when subsequently exposed to the pertinent MHC alloantigens in immunogenic form but unaltered MHC-third party responsiveness of the naive spleen T cells. Furthermore, the accessory function of this clone is strongly reduced. These functional defects could be overcome by the addition of exogenous interleukin-1 alpha (IL-1 alpha). Analysis of mRNA expression showed a significant and selective reduction of IL-1 alpha mRNA levels when compared with parental cells.

Animals↗
PubMed1993

Interleukin-4 bypass of the immunosuppressive effect mediated by interleukin-2 receptor antibodies.

Numerous studies have demonstrated that the generation of alloreactive effector cells depends on cytokines. Conversely, there is evidence that cytokine metabolism is altered at the clonal level in tolerant chimaeras. This has led to preclinical and clinical studies using antibodies that antagonize interleukin-2 (IL-2), with the hope of achieving immunosuppression and inducing tolerance. Monoclonal antibodies against the alpha-chain (p55) of the human IL-2 receptor are being applied to prevent transplant rejection and graft-versus-host disease in several clinical trials. The antibodies that have been applied clinically so far antagonize the binding of IL-2 to the IL-2 receptor alpha-chain which is part of the high affinity IL-2 receptor, but they do not deplete the receptor-bearing cells. Our study investigates the immunosuppressive effect of monoclonal antibodies against the alpha-chain (p55) and beta-chain (p75). In mixed lymphocyte cultures the p55 antibody causes a reduction in T-cell proliferation to about 50%. The generation of cytotoxic T cells is reduced more effectively (up to 80%). By additional blocking of the IL-2 receptor beta-chain we achieved an additional but still incomplete immunosuppressive effect. Moreover we show that IL-2 receptor-blocked alloreactive T cells escape suppression by using IL-4 as an alternative stimulating signal. To prevent T lymphocytes benefiting from this alternative and thwarting the immunosuppressive effect, cytotoxic IL-2 receptor antibodies that deplete the high affinity receptor-bearing cells are needed.

Antibodies↗
PubMed1993

In vitro cultivation and immunogenicity of human cardiac valve endothelium.

Endothelial cells were derived from aortic and mitral valves (n = 17) by collagenase digestion and subsequently cultivated in RPMI medium supplemented with 20% fetal calf serum. The cells were stained in an alkaline phosphatase-anti-alkaline phosphatase stain for the expression of MHC Class I and Class II antigens, ICAM-1, ELAM-1, F VIII, and H/Y. The endothelium showed a strong expression of Class I, H/Y, and ICAM-1 molecules, and weak expression of MHC Class II molecules. In contrast to vascular endothelium that is known to express F VIII constitutively, cardiac valve endothelium was found to be negative. F VIII and ELAM-1 were only expressed after stimulation with recombinant interferon-gamma. To analyze the immunogenicity of valve endothelium, cells were used as stimulator cells in a mixed cell culture reaction using lymphocytes as responder cells. Endothelial cells had a 2 to 3 times higher stimulatory effect than peripheral blood lymphocytes. These data allow speculation on whether the observed degeneration of homografts can be reduced if HLA matching is performed prior to valve implantation.

Cell Adhesion Molecules↗
PubMed1993

The hematopoietic system influences odor specificity in mice and rats.

The change in strain-specific urine odors which appears after bone marrow transplantations was examined in mice and rats in order to demonstrate an influence of the hematopoietic system on urinary chemosignals. Four rats were trained in an olfactometer to discriminate two allogeneic mouse or rat strains via their urine odors. Urine samples obtained from two inbred strains of mice, from two inbred strains of rats, from allogeneic reconstituted mice, and from semiallogeneic reconstituted rats were combined in a number of 'transfer of training' tests. Results confirm findings that the hematopoietic system influences odor specificity in mice. For the first time a change of urinary chemosignals after bone marrow transplantation in rats was demonstrated by using semiallogeneic reconstituted rat chimeras.

Animals↗