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Biomedical subjects

G Riethmüller

Publications and source records attributed to G Riethmüller.

At least 127 records · Page 7Linked to original sources
PubMed1991

Treatment of rheumatoid arthritis with monoclonal CD4 antibody M-T151. Clinical results and immunopharmacologic effects in an open study, including repeated administration.

Recent experimental and clinical data point to the T helper lymphocyte subset as playing a central role in the pathogenesis of rheumatoid arthritis (RA). Thus, a therapeutic strategy aimed specifically at the CD4 T cell subset is warranted. We treated patients with active RA for 7 days with a daily dose of 20 mg of CD4 monoclonal antibody M-T151, administered intravenously over 30 minutes. There were no negative side effects. According to changes in the combined parameters of Ritchie articular index, pain assessment, grip strength, and morning stiffness, 6 patients had a good response. Clinical improvement was greatest approximately 2 weeks after termination of the therapy and lasted from 4 weeks to 6 months. Of the serologic parameters of inflammation, only the C-reactive protein level improved in the patients with a favorable response. Close immunologic monitoring revealed a transient, selective depletion of CD4+ T cells after each infusion. During the entire treatment period, residual circulating CD4+ cells were found to be coated with CD4 antibody, whereas free antibody was detected in the serum only for approximately 8 hours after each infusion. Immediately after infusion, soluble CD4 antigen appeared in the serum. In addition to the cell-bound CD4 antibody, complement components could be detected on the surface of the remaining CD4+ cells. The proliferative response of peripheral blood mononuclear cells to purified protein derivative was significantly diminished 4 weeks after cessation of antibody treatment. Six patients showed a weak antibody response to mouse immunoglobulin. In 4 of the responders who received a second course of therapy (2 of them as outpatients), a therapeutic effect was noted that was similar to that after the first course. Only 1 patient, who had low titers of serum IgE anti-mouse Ig antibodies, showed a mild anaphylactic reaction at the end of the second course of therapy. Treatment of RA with the monoclonal CD4 antibody M-T151 seems to be a promising alternative, although the optimal dose and the regimen of administration are still to be defined.

Animals↗
PubMed1991

Hepatitis B virus antigen-specific T-cell activation in patients with acute and chronic hepatitis B.

Since the hepatitis B virus is noncytopathic, it is generally believed that the individual specific immune response determines the course of infection. The lack of data about hepatitis B virus-specific T-cell reactions in acute infection led us to investigate the specific cellular immune response of infected individuals in terms of proliferation, and gamma-interferon and lymphotoxin production. Our results demonstrate that peripheral blood mononuclear cells (PBMNC) from patients with acute and chronic hepatitis B respond weakly to HBsAg. In contrast, patients with acute hepatitis show a vigorous response to the nucleocapsid antigen (HBcAg) in terms of proliferation and lymphokine production, while only few chronic virus carriers gave a proliferative response. Either of the antigens could activate lymphocytes to produce gamma-interferon and lymphotoxin, cytokines which may modulate antiviral immune response.

Acute Disease↗
PubMed1991

Micrometastatic tumour cells in bone marrow of patients with gastric cancer: methodological aspects of detection and prognostic significance.

Monoclonal antibodies (Mab) are potent probes to identify individual tumour cells or small tumour cell clusters in bone marrow. In the present study, various antibodies directed against either cell surface or intracytoplasmic antigens of epithelial cells were assessed for their ability to detect such cells in bone marrow of patients with breast, colorectal and gastric cancer. According to the presented data, monoclonal antibodies against intracellular cytokeratin (CK) components are superior in terms of specificity and sensitivity to antibodies reacting with epitopes of the cell membrane. Using a monoclonal antibody against the cytokeratin polypeptide 18 in connection with the alkaline phosphatase anti-alkaline phosphatase detection system (APAAP), we could detect tumour cells in bone marrow of 34 out of 97 patients with gastric cancer examined at the time of primary surgery. The incidence of positive findings was correlated to established risk factors, such as histological classification and locoregional lymph node involvement. Clinical follow-up studies on 38 patients demonstrated a significantly increased relapse rate in patients presenting with CK-positive cells in their bone marrow at the time of primary surgery. Thus the described technique may help to identify patients with gastric cancer carrying a high risk of early relapse.

Antibodies, Monoclonal↗
PubMed1991

Anti-idiotypic antibodies against anti-CD4 antibodies MT151 and OKT4A.

Anti-idiotypic antibodies (Ab2) binding to the antigen-combining site of other antibodies may functionally and even structurally mimic antigen. Ab2 to antibodies directed against the lymphocyte CD4 receptor for human immunodeficiency virus type 1 (HIV-1) may mimic the receptor and therefore inhibit viral infectivity. We have produced Ab2 against monoclonal anti-CD4 receptor antibodies (Ab1). The Ab1 strongly inhibit HIV-1 binding to the receptor. Six monoclonal rat Ab2 and two polyclonal rabbit Ab2 were produced against the Ab1 MT151 and nine monoclonal Ab2 against the Ab1 OKT4A. These Ab2 bound only to Ab1 and not to a panel of nine unrelated murine monoclonal antibodies (MAbs). The Ab2 completely inhibited the binding of the homologous Ab1 to CD4-positive target cells, and recombinant soluble CD4 inhibited binding of Ab2 to Ab1. Thus, the Ab2 seemed to mimic the Ab1-binding site of the CD4 receptor, although the results of inhibition assays did not exclude steric hindrance of antibody-combining sites. However, none of the 17 Ab2 bound to gp120 of HIV-1 envelope or inhibited syncytia formation between cells infected and uninfected with HIV-1. These results suggest that the Ab2 do not mimic the HIV-1 binding site of the CD4 receptor. They further suggest that the Ab1 may not bind within the virus-binding site of the CD4 receptor.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Expression of intercellular adhesion molecule-1 (ICAM-1) in the skin of patients with systemic scleroderma.

The expression and tissue distribution of intercellular adhesion molecule-1 (ICAM-1) in skin biopsies from 12 patients with systemic (SSc) and localized (LS) scleroderma was studied and compared to the biopsies from patients with lupus erythematosus (LE) and normal individuals. In normal human skin ICAM-1 expression was restricted to the vascular endothelium, infiltrating mononuclear cells (MNC), and to few individual keratinocytes. In the inflammatory stage of SSc, however, the expression of ICAM-1 was dramatically increased at the site of MNC infiltrates and could also be detected on fibroblast-like cells lying well apart from these infiltrates in the deep dermis. In contrast, in LS ICAM-1 was expressed mainly at the sites of MNC infiltrates. In LE ICAM-1 expression was confined to the keratinocytes, endothelial cells, and mononuclear cells in the upper parts of the dermis. Analysis of serial tissue sections from patients with SSc demonstrated also colocalization of staining of ICAM-1 around blood vessels with LFA-1-positive lymphocytes. Increased expression of ICAM-1 in the dermis of patients with SSc may represent an important mechanism by which MNC become localized and retained at a site of connective tissue inflammation, leading to the activation of fibroblasts.

Adult↗
PubMed1991

Vascular deposition of complement-split products in kidney allografts with cell-mediated rejection.

Complement activation in 73 renal transplant biopsies was investigated by indirect immunoperoxidase staining using MoAbs reactive with complement-split products. Intense deposition of complement fragments C4d and C3d in peritubular capillaries, indicating activation of the classical pathway, could be detected in the majority of transplanted kidneys with cell-mediated rejections. Abundant deposition of complement-split products was observed in 22 early biopsies from patients with high 'immunological risk' (i.e. previous, rejected transplants and/or circulating antibodies against HLA-antigens). Despite negative results in the crossmatch before transplantation and paucity of immunoglobulins in transplant biopsies, antibodies directed against endothelial cell antigens should be considered as a possible cause of classical complement activation.

Antibodies, Monoclonal↗
PubMed1991

Allelic variation in the TNF-beta gene does not explain the low TNF-beta response in patients with primary biliary cirrhosis.

Autoimmune disorders in humans are often associated with particular alleles of major histocompatibility genes. However, the chronic inflammatory liver disease primary biliary cirrhosis (PBC) has not been found to be correlated with certain haplotypes so far. Interestingly, an impaired production of tumour necrosis factor beta (TNF-beta) upon mitogen stimulation was observed for PBC patients, especially in the immunologically active stages of the disease. Furthermore, the identification of alleles of the TNF-beta gene which differ in one unique amino acid, and in the production of TNF-beta after phytohaemagglutinin stimulation, has prompted the idea of a possible linkage between the impaired TNF-beta response in PBC and the genetic prevalence of a certain TNF haplotype. We report here a rapid method for typing the TNFB*1 and TNFB*2 genes by a standard polymerase chain reaction. PBC patients (n = 60) as well as randomized healthy controls (n = 179) of the Munich area were studied for the occurrence of the TNF alleles. No deviation was found in the PBC collective (0.7) for the TNFB*2 distribution when compared with the control (0.67).

Alleles↗
PubMed1991

Quantitative analysis of CD6, CD4 and CD8 cell surface molecules compared to the absolute numbers of CD6+, CD4+ and CD8+ T-cells in peripheral blood in patients with HIV-infection.

T lymphocyte subsets were determined on blood samples from 16 HIV-seropositive patients with manifest AIDS (CDC IV), 24 HIV-seropositive patients with lymphadenopathy syndrome (LAS, CDC III), 16 HIV-seropositive clinical healthy persons (CDC II) and 11 HIV-seronegative homosexuals as control group. Absolute numbers of T-cells (CD6+), T-helper/inducer-cells (CD4+) and T-suppressor/cytotoxic-cells (CD8+), obtained by immunofluorescence staining were compared with the absolute amount of subset specific surface molecules, obtained by a T-cell-ELISA. With both, indirect immunofluorescence technique and ELISA technique a highly significant decrease of the absolute numbers of CD4+ cells and the absolute amount of CD4 surface molecules, respectively, was found in asymptomatic HIV-infection, LAS and in manifest AIDS. In all HIV-seropositive groups the relative decrease of CD4 surface molecules was significantly greater than the decline of CD4+ cells. This phenomenon however was not seen in HIV-seronegative homosexuals. The absolute number of CD6+ cells and the amount of CD6 surface molecules were found significantly lowered in AIDS compared to HIV-seronegative homosexuals. No significant changes were found for CD8+ cell numbers and CD8 surface molecule in the progression of the HIV-infection.

Antigens, CD↗
PubMed1991

Immune response of peripheral blood mononuclear cells to HBx-antigen of hepatitis B virus.

The hepatitis B virus genome encodes a transcriptional transactivator protein designated HBxAg. We have investigated whether this antigen is a target structure for human T-lymphocytes. Using recombinant HBxAg protein, we found HBxAg-specific stimulation of peripheral blood mononuclear cells in patients with acute hepatitis B virus infection (6 of 6) and chronic hepatitis B virus infection (6 of 17) but not in healthy individuals. With HBxAg-specific synthetic polypeptides, several T-cell epitopes were identified. Most were located in the carboxyterminal half of the HBxAg protein. Five T-cell clones specific for a T-cell epitope located at the carboxyterminal region of HBxAg were established and found to belong to the CD2/CD4-positive, CD8-negative subtype. These data establish for the first time HBxAg as an antigen in the cellular immune response.

Acute Disease↗
PubMed1990

Deficient production of tumor necrosis factor by peripheral-blood monocytes in chronic lymphocytic leukemia.

The production of tumor necrosis factor (TNF) by lipopolysaccharide (LPS)-triggered peripheral-blood mononuclear cells (PBM) was investigated in 23 patients with untreated B-cell chronic lymphocytic leukemia (B-CLL) and 14 control donors. Cells were stimulated at concentrations that reflect cell density in peripheral blood. Under these conditions, PBM from 11/23 of the CLL patients produced at least 10-fold less TNF as compared with controls. Monocyte numbers were decreased in percentage, while absolute numbers (normal range 233 +/- 120 X 10(3)/mm3) were decreased only in 2, normal in 17 and increased in 4 patients indicating that the deficiency is not a result of monocytopenia in most patients. Cell separation experiments indicate that after removal of leukemic B cells, percentages of monocytes return to control range and TNF production is improved (7/7). In mixing experiments, we found a suppression of TNF production in control mononuclear cells by CLL cell samples (75 X 10(6) cells/ml) in 5/19 cases, while control cells from thymus exhibited no or little suppression in these conditions. In 2-chamber experiments, leukemic samples suppress TNF production by normal monocytes across a 0.45 micron membrane indicating that a soluble factor is responsible for suppression. The factor exhibits higher stability in serum-free conditions and its molecular weight is below 20 kDa. Prostaglandins are not involved, since indomethacin did not abrogate suppression.

Aged↗
PubMed1990

Inhibition of lipopolysaccharide-induced in vitro desensitization by interferon-gamma.

Exposure of Mono-Mac-6 cells to lipopolysaccharide (LPS) can induce rapid and transient expression of cytokines like tumor necrosis factor (TNF), interleukin 1 and interleukin 6. Preculture of Mono-Mac-6 cells in culture medium containing small amounts (1-50 ng/ml) of LPS for 3 days leads to an unresponsiveness to a subsequent stimulation with a high amount of LPS. This in vitro desensitization of a monocytic cell line may serve as a model for desensitization to LPS seen in vivo, for example in mice or man repetitively treated with LPS. Addition of interferon-gamma (IFN-gamma) to the Mono-Mac-6 cells during the LPS preculture period leads to an inhibition of desensitization, whereas addition of IFN-alpha or IFN-beta is not able to inhibit the LPS-induced desensitization. The inhibition of desensitization by IFN-gamma was dose dependent and time dependent. Preculture of Mono-Mac-6 cells with LPS leads to a strong reduction of TNF mRNA. This reduction of specific mRNA is also overcome by addition of IFN-gamma, but not by IFN-alpha and IFN-beta, indicating that pretranslational mechanisms are responsible for the regulation of TNF in desensitization.

Cell Line↗
PubMed1990

Inverse relationship of CA2+ mobilization and cell proliferation in CD8+ memory and virgin T cells.

Memory T cells can now be defined with various monoclonal antibodies but little is known about the functional properties of these cells as compared to virgin T cells. We have studied Ca2+ mobilization and proliferation of memory and virgin cells in both the CD4 and CD8 subsets in response to phytohemagglutin-in. Using two-color fluorescence (yellow, red) for cell surface staining combined with two-color fluorescence for the Ca2+ chelator indo-1 (violet, blue) we can demonstrate that CD8+UCHL1+ memory cells exhibit a 1,5-fold higher influx than the CD8+UCHL1- virgin cells. The same pattern was obtained when CD8 memory and virgin cells were defined by a reciprocal marker (Leu-18) indicating that the higher response of memory CD8 cells is independent of the monoclonal antibody used to identify the cells. For the respective CD4 subsets no such clear-cut pattern of Ca2+ influx was evident. Analysis of proliferation in both subsets indicates that CD8+UCHL1- cells strongly proliferate in response to PHA, while CD8+UCHL1+ memory cells show only a minimal response with the average cpm values being 6-fold lower. In some instances no proliferation at all was detectable in the CD8+UCHL1+ cells. Identification of the subsets by reciprocal markers confirmed the lower proliferative response in the CD8 memory cells. Hence, within the CD8 compartment the memory cells, after phytohemagglutinin stimulation, exhibit a high Ca2+ mobilization but a low to absent proliferation, while the converse is true for the naive cells. These data show that (a) Ca2+ mobilization and proliferation are inversely correlated and (b) an initially vigorous response of memory cells may be subject to negative control mechanisms.

Antigens, Differentiation↗
PubMed1990

Structural characteristics of the 5' region of the human ICAM-1 gene.

The ICAM-1 glycoprotein, one of the major cellular adhesion molecules, exhibits a diverse and highly regulated tissue distribution. To better understand the regulatory mechanisms underlying its particular expression pattern, we have cloned the ICAM-1 gene from human leukocyte libraries. By hybridization with various DNA probes derived from different regions of the ICAM-1 cDNA, several clones were identified and isolated. Clone HWB 3R1, containing a 15kb DNA insert, was selected for further characterization. The HWB 3R1 clone hybridized with probes corresponding to the 3' as well as the 5' region of the ICAM-1 cDNA and gave rise to ICAM-1 expression after transfection into the ICAM-1 deficient MJP17 melanoma cell line. The identity of the expressed ICAM-1 was verified by reaction with five different monoclonal antibodies specific for ICAM-1. Sequence analysis of about 1.2kb of DNA around the ATG start codon revealed putative binding sites for various transcription factors situated in the 5' untranslated region as well as within the first intron. These include SP-1, AP-1 and NF-kB binding sites as well as interferon and retinoic acid responsive elements.

Amino Acid Sequence↗
PubMed1990

Molecular mechanisms in down-regulation of tumor necrosis factor expression.

Excessive production of tumor necrosis factor (TNF) after stimulation by lipopolysaccharide (LPS) may result in fever, intravascular coagulation, and lethal shock. An efficient way of preventing the excessive TNF production is desensitization of monocytes/macrophages to LPS. We have analyzed the molecular mechanisms involved in the induction of desensitization and the mechanisms operative in the desensitized, LPS-refractory cells by employing the human monocytic cell line Mono-Mac-6. Similar to human blood monocytes, treatment of Mono-Mac-6 cells with LPS (1 microgram/ml) results in a rapid and transient expression of TNF. When Mono-Mac-6 cells are precultured in medium containing low levels of LPS, they become refractory to subsequent LPS stimulation and show no or little secretion of TNF protein. Desensitization can be blocked by the inhibition of cyclooxygenase and protein kinase C; both prostaglandin E2 (together with a second signal) and phorbol 12-myristate 13-acetate can mimic desensitization. By employing prostaglandin E2 and low concentrations of phorbol 12-myristate 13-acetate, a synergism in the induction of desensitization can be demonstrated. Hence, our studies show that two distinct pathways are involved in the induction of hyporesponsiveness. In both LPS-responsive and LPS-desensitized Mono-Mac-6 cells, LPS was able to induce the transcription factor NF-kappa B in the nucleus. Still, the prevalence of TNF-specific mRNA was dramatically reduced in the desensitized cells. These data indicate that LPS-desensitized Mono-Mac-6 cells are able to activate initial steps of signal transduction up to the level of the NF-kappa B transcription factor. The absence of TNF transcripts, however, indicates that additional nuclear factors may be missing or that silencers may be active such that transcription of the TNF gene is prevented.

Animals↗
PubMed1990

Infection of the human monocytic cell line Mono Mac6 with human immunodeficiency virus types 1 and 2 results in long-term production of virus variants with increased cytopathogenicity for CD4+ T cells.

The recently established human monocytic cell line Mono Mac6 expressing distinct characteristics of mature monocytes/macrophages was tested for its susceptibility to infection with human immunodeficiency virus. Inoculation of the cells with the T-cell-tropic human immunodeficiency virus strains human T-lymphotropic virus type IIIB and lymphadenopathy-associated virus type 2 led to a noncytopathic productive infection becoming apparent only after a latency period of up to 56 days. The infectibility of the Mono Mac6 cells was dependent on low levels of CD4 expression, as demonstrated by blocking experiments with various CD4-specific antibodies. Increasing with time after infection (greater than 200 days), the cultured Mono Mac6 cells released virus variants which showed shortened latency periods when passaged onto uninfected Mono Mac6 cells. Also, cytopathogenicity for several CD4+ T cells of the Mono Mac6-derived virus was drastically increased; thus, the infection of the H9 cell line with low doses of virus (less than 0.1 50% tissue culture infective dose per cell) led to giant syncytium formation within 1 day and subsequent death of all fused cells. We propose Mono Mac6 cells as a new model for the study of human immunodeficiency virus infecting the monocyte/macrophage lineage, particularly with regard to virus-host cell interaction and the influence of cell differentiation and activation on latency and development of virulence. The human immunodeficiency virus-infected Mono Mac6 cell may also serve as a valuable tool for in vitro testing of antiviral therapies.

CD4 Antigens↗
PubMed1990

Epithelial tumor cells in bone marrow of patients with colorectal cancer: immunocytochemical detection, phenotypic characterization, and prognostic significance.

A monoclonal antibody (mAb) directed against the cytokeratin (CK) polypeptide no. 18 specifically expressed in cells derived from simple epithelia was used to detect epithelial tumor cells in bone marrow aspirates. Of 156 patients with colorectal carcinoma, 42 presented with cells at the time of primary surgery. The incidence of positive findings varied considerably with the size and the localization of the primary tumor, the involvement of regional lymph nodes, and the presence of clinically manifest metastases. Applying a sensitive double-staining procedure, we could demonstrate that epithelial cells in bone marrow showed a heterogeneic expression of receptors for epidermal growth factor (EGF-R) and transferrin (Tf-R) as well as of the proliferation-associated Ki67 antigen. Also human leukocyte antigen (HLA) class I antigens differed widely in their expression on the CK-positive cells. Clinical follow-up studies on 85 patients showed a significantly higher relapse rate in patients presenting with CK-positive cells in their bone marrow at the time of primary surgery. Twenty-three patients were monitored for the presence or absence of CK-positive cells in bone marrow over time. The majority of monitored patients (18 of 23) exhibited a constant pattern of immunocytochemical findings during the time of observation. Thus, the technique may be useful in identifying high-risk patients as well as in monitoring adjuvant therapeutic trials.

Antibodies, Monoclonal↗