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Biomedical subjects

F Emmrich

Publications and source records attributed to F Emmrich.

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

Preincubation with anti-CD4 influences activation of human T cells by subsequent co-cross-linking of CD4 with CD3.

Under physiological conditions, T cell activation by major histocompatibility complex (MHC)-antigen complexes requires engagement of both the T cell receptor (TcR) and the CD4 (or CD8) accessory molecules. It has been shown, however, that ligation of CD4 and CD8 can also inhibit T cell activation in an MHC-independent way. Therefore, the role of CD4 in T cell activation and the mechanism of the suppression of T cell functions by anti-CD4 are as yet unclear. We activated T cells by CD4/CD3 co-cross-linking and studied the effect of preincubation with anti-CD4 on this activation. We show here that anti-CD4 effects T cell activation in a complex, time-dependent manner. Whereas short preincubations with anti-CD4 usually enhanced T cell proliferation in response to subsequent co-cross-linking of CD3 with CD4, longer preincubations led to its decrease. The observed suppression of proliferation after a long preincubation with anti-CD4 was apparently due to impairment of TcR signaling, as assessed by measurement of Ca2+ mobilization and tyrosine phosphorylation in T cells. These results add a temporal element to the previously observed synergism between the TcR and CD4 in T cell activation.

Antibodies, Monoclonal↗
PubMed1993

Human CD4 modulation in vivo induced by antibody treatment.

Clinical improvement after treatment with anti-CD4 antibodies has been documented in patients suffering from rheumatoid arthritis. This observation has stimulated the interest in effects induced by the in vivo application of anti-CD4 antibodies. Here, we have investigated features of CD4 modulation during and after anti-CD4 therapy with the monoclonal anti-body MAX.16H5. Depletion of circulating helper T cells was accompanied by modulation of the CD4 molecule down to 30% of the initial antigen density 1 hr after antibody infusion. However, despite the reappearance of CD4+ cells in the circulation CD4 remained down-modulated for up to 28 days without a significant residual anti-CD4 binding. Depletion of CD4+ cells as well as CD4 modulation were observed to a similar extent both in responders and non-responders to anti-CD4 therapy. Modulation of CD4 was more effective in vivo than in vitro with a mean reduction of CD4 density down to 46% in vitro. It was induced in varying degrees by all anti-CD4 antibodies investigated except for OKT4 and required viable monocytes in the case of MAX.16H5 and most of the anti-CD4 antibodies investigated. Supernatants from LPS-activated monocytes or the addition of monocytes that were freeze-fractioned or fixed monocytes did not substitute for this requirement. The effect was Fc-receptor dependent since F(ab)2 fragments of MAX.16H5 did not induce CD4 modulation. No significant co-modulation was found for a variety of T-cell surface antigens including CD2, CD3, CD8, CD45R, CD45RO, CD25, CDw29, and HLA-DR. In order to test functional effects, the influence of CD4 modulation on the increase of free cytosolic Ca2+ concentration ([Ca2+]i) stimulated via the T-cell receptor complex by an anti-CD3 antibody was studied. A significant inhibition was observed upon direct binding of anti-CD4 to its ligand. However, a diminished CD4 density alone as induced by in vivo modulation did not reduce, but rather enhanced the T cell receptor-mediated mobilization of [Ca2+]i in T cells of the patients. Taken together, no evidence was found that CD4 modulation per se could explain the beneficial effects of anti-CD4 therapy.

Adjuvants, Immunologic↗
PubMed1993

Interleukin-6 in synovial fluid is closely associated with chronic synovitis in rheumatoid arthritis.

Interleukin-6 (IL-6) was detected at low levels in plasma [0.014 +/- 0.006 ng/ml (mean +/- SEM] and in high amounts in synovial fluid [SF; 2.6 +/- 2.2 ng/ml (mean +/- SEM)] of patients with rheumatoid arthritis. No correlation of IL-6 levels in plasma or SF with the ESR (n = 15) or with histological parameters of acute local synovitis (n = 10) was observed. In contrast, SF IL-6 was positively correlated with histological characteristics of chronic synovitis (n = 10; P < or = 0.01) and elevated plasma IgG concentrations (n = 15; P < or = 0.05). In vitro concentrations of IL-6 comparable to those detected in SF increased the production of both IgG and IgM by synovial membrane mononuclear cells. The present results contribute to the view that high local IL-6 concentrations in SF promote chronic synovitis in RA.

Adult↗
PubMed1993

Advances in immunotherapy of rheumatoid arthritis: clinical and immunological findings following treatment with anti-CD4 antibodies.

Rheumatoid arthritis is a chronic inflammatory disease mainly affecting the joints. The etiology of the disease is still unknown, but it shows several of the clinical and laboratory features of an autoimmune process. Often, efficacy of conventional treatment is not satisfactory in patients with RA and therefore, alternative therapies have to be considered. Since CD4+ T helper cells appear to play an important role in disease pathogenesis, anti-CD4 treatment has been tried in RA patients. This paper will present a summary of our experience including some new recent findings upon immunomodulation caused by anti-CD4. Following anti-CD4 antibody infusion with antibody MAX16H5, a decline in lymphocyte counts has been observed with a depletion of CD3+ T cells to 30%, CD4+ T cells to 13% and monocytes to 33% of pretreatment levels. Moreover, all remaining T helper cells were coated by anti-CD4. No changes in CD8+ T cells or B lymphocytes were noted. After a partial recovery of CD4+ T cells, decreased numbers were maintained for 8 weeks. Modulation of the target antigen was demonstrated by high levels of soluble CD4 and a decreased CD4 antigen density on T helper cells down to 30% of the original level, which reached pretreatment levels 2 weeks after therapy. Proliferative responses to mitogens and antigens were reduced immediately after the antibody infusions but were markedly increased in some patients when compared to the pretreatment situation. In addition, a rapid decrease of monocyte/macrophage activation markers was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
PubMed1993

Comparison of 99Tcm-labelled specific murine anti-CD4 monoclonal antibodies and nonspecific human immunoglobulin for imaging inflamed joints in rheumatoid arthritis.

Inflamed joints in human rheumatoid arthritis (RA) can be imaged employing 99Tcm-labelled anti-CD4 monoclonal antibodies (MAbs). These MAbs recognize the CD4 molecule expressed on T-helper cells and, with a lower density, on macrophages, which are both abundantly present in RA inflammatory infiltrates. However, it is at present unclear whether specific binding to target molecules in the inflamed joint determines the joint uptake of anti-CD4 MAbs, i.e. whether the uptake of anti-CD4 MAbs differs from that of control immunoglobulins with irrelevant specificity. Eight patients with severe, active RA were examined after intravenous injection of a 99Tcm-labelled murine anti-human CD4 MAb (MAX.16H5; 200-300 micrograms, 370-550 MBq) or polyclonal human immunoglobulin (HIG; Technescan, MDH-67, Mallinckrodt Diagnostica; 1 mg, 370 MBq); five patients received both the anti-CD4 MAb and HIG. Whole body and joint scans in anterior and posterior views were obtained 1, 4 and 24 h after injection. As early as 4 h after injection, the anti-human CD4 MAb showed a higher target-to-background ratio in arthritic knee and elbow joints in comparison to polyclonal HIG used for conventional imaging, indicating that that anti-CD4 MAb allows more specific detection of inflammatory infiltrates rich in CD4-positive cells.

Adult↗
PubMed1993

Reduction of monocyte-macrophage activation markers upon anti-CD4 treatment. Decreased levels of IL-1, IL-6, neopterin and soluble CD14 in patients with rheumatoid arthritis.

Anti-CD4 MoAbs have been successfully used in initial treatment trials of rheumatoid arthritis. One remarkable feature of this therapy was the early reduction of synovitis along with a decrease of the erythrocyte sedimentation rate (ESR) and the C-reactive protein (CRP). Since not only T helper cells, but also monocytes-macrophages bear the CD4 antigen, the question was raised whether the immediate effects observed may have been in part due to an influence on the mononuclear phagocyte system. Immediately after MoAb infusions, a significant reduction of the absolute peripheral blood monocyte count down to 30% (P < 0.001) was noted within the first hour of injection. In contrast to strikingly elevated levels of soluble CD4 after treatment which was indicative of T cell lysis, soluble CD14 levels did not rise, but rather decreased from previously elevated levels. Before treatment, activation of the monocyte-macrophage system had been signified by elevated serum levels of IL-1, IL-6, CRP and neopterin as well as a marked in vitro production of IL-1, tumour necrosis factor-alpha (TNF-alpha) and IL-6. Subsequent anti-CD4 treatment resulted in a rapid and significant reduction of monocyte-derived circulating cytokines and mediators concordant with a reduced capacity to produce IL-1, TNF-alpha, and IL-6 in those patients who demonstrated clinical benefits. Therefore, studies of monocyte activation markers may be useful in identifying subsequent responders to anti-CD4 therapy.

Antibodies, Monoclonal↗
PubMed1993

Outer membrane protein YadA of enteropathogenic yersiniae mediates specific binding to cellular but not plasma fibronectin.

The binding of bacteria or bacterial products to host proteins of tissue extracellular matrix may be a mechanism of tissue adherence. We investigated interactions of the plasmid-encoded outer membrane protein YadA, which confers pathogenic functions on enteropathogenic yersiniae, with fibronectin. Attachment of YadA-positive and YadA-negative recombinant Yersinia enterocolitica strains to cartilage-derived human cellular fibronectin and human plasma fibronectin in the solid phase revealed that YadA mediates binding of yersiniae to cellular fibronectin in a saturable, concentration-dependent manner. The interaction could be inhibited by an anti-YadA-specific anti-serum. An anti-beta 1-integrin antibody and the synthetic peptide G-R-G-D-S-P, representing the binding site for alpha 5 beta 1-integrin on fibronectin, did not block attachment of YadA-positive yersiniae to cellular fibronectin, indicating a binding site for YadA on cellular fibronectin independent of the R-G-D-S-containing site. By contrast, YadA failed to mediate binding to plasma fibronectin immobilized on nitrocellulose or plastic surfaces. These observations provide evidence for the hypothesis that the binding region for YadA in cellular fibronectin is not present in plasma fibronectin. This study is the first report on differential binding of bacteria to splicing variants of fibronectin. Further experiments might answer the question whether binding of YadA to cellular fibronectin contributes to the pathogenesis of yersiniae, both to the initial adhesion of the bacteria to the matrices of the host and to the arthritogenic potential of enteropathogenic yersiniae.

Adhesins, Bacterial↗
PubMed1993

[Follow-up study of the development of autoantibodies in patients with chronic inflammatory bowel disease under anti-CD4 therapy].

7 of 22 patients with chronic inflammatory bowel diseases (Crohn's disease, ulcerative colitis) were treated with an anti-CD4-mAb. In the immunological monitoring the amounts of autoantibodies to pancreatic acini cells, to intestinal goblet cells, to granulocytes with perinuclear fluorescence pattern were examined and human anti-mouse-antibodies were measured. After anti-CD4 therapy the production of autoantibodies was widely unchanged. Therefore its use as parameter in the follow-up is restricted.

Antibodies, Monoclonal↗
PubMed1993

Joint uptake and body distribution of a technetium-99m-labeled anti-rat-CD4 monoclonal antibody in rat adjuvant arthritis.

Joint uptake and body distribution of a 99mTc-labeled monoclonal antibody (Mab) to the rat CD4 molecule (W3/25; IgG1) were investigated after intravenous injection in normal rats and in animals with experimentally induced adjuvant arthritis. An isotype-matched Mab with irrelevant specificity (anti-human carcino-embryonic-antigen) was used as control. A 4 hr sequential gamma-camera imaging revealed that both anti-CD4 and control Mab accumulated to a higher degree in arthritic than in normal ankle joints; the accumulation was comparable for the two Mabs. In contrast to the inflamed joints, a specific accumulation of the anti-CD4 Mab was found in organs rich in CD4-positive cells, i.e. spleen, bone marrow and lymph nodes, as assessed by direct well counter measurements 16 hr after injection. The control Mab displayed no preferential organ accumulation in either normal or diseased animals. These results indicate that a specific accumulation of anti-CD4 Mabs occurs in CD4-positive-cell-rich tissues in both normal and diseased animals and that immunoglobulins accumulate preferentially in inflamed joints regardless of their antibody specificity.

Animals↗
PubMed1992

D-myo-inositol 1,3,4,5-tetrakisphosphate releases Ca2+ from crude microsomes and enriched vesicular plasma membranes, but not from intracellular stores of permeabilized T-lymphocytes and monocytes.

In the human T-lymphocyte cell lines Jurkat and HPB.ALL and the human monocytoid cell line U937, Ins(1,3,4,5)P4 triggers a dose-dependent release of Ca2+ from crude microsomal preparations, with a half-maximal effective concentration (EC50) of 1.2-2.3 microM. Similar results were obtained with enriched vesicular plasma membranes from U937 cells. However, in permeabilized preparations of the same cell types only Ins(1,4,5)P3 was able to release Ca2+ from intracellular stores, with EC50 values in the range 0.11-0.84 microM. In crude microsomes the effects of Ins(1,3,4,5)P4 and Ins(2,4,5)P3, a non-metabolizable InsP3 isomer, occurred independently of each other, indicating subpopulations of Ins(1,3,4,5)P4- and Ins(1,4,5)P3-sensitive vesicles. The Ins(1,3,4,5)P4 preparation used for the Ca(2+)-release experiments contains neither Ca2+ nor contaminating Ins(1,4,5)P3 and was not metabolized to Ins(1,4,5)P3 during the Ca(2+)-release experiments. We conclude that Ins(1,3,4,5)P4 independently of Ins(1,4,5)P3 induces a Ca2+ flux via a membrane compartment, most likely the plasma membrane, that is functionally destroyed during the permeabilization of the cells.

Calcium↗
PubMed1992

Complex inositol polyphosphate response induced by co-cross-linking of CD4 and Fc gamma receptors in the human monocytoid cell line U937.

The cell-surface Ag CD4, which is characteristic for Th lymphocytes, can also be found with a lower density on monocytes/macrophages. Co-cross-linking of CD4 and Fc gamma R by an anti-CD4 mAb (MAX.16H5) and by excess of goat anti-mouse Ig induced a biphasic increase of the free cytosolic Ca(2+)-concentration ([Ca2+]i) in the human monocytoid cell line U937 as measured by FURA-2 fluorescence. A rapid rise from 100 to 150 nM [Ca2+]i to 750 to 900 nM within 1 min was followed by a decline to about 200 to 300 nM within the next 2 to 3 min. This kinetic is characteristic also for blood monocytes and differs significantly from CD4-mediated Ca(2+)-mobilization in T lymphocytes. The rise in [Ca2+]i in U937 cells was not observed when F(ab)2 fragments of MAX.16H5 and F(ab)2 fragments of the cross-linker were used indicating the involvement of Fc gamma R. Time course analysis using HPLC and a recently developed post-column dye system for mass analysis revealed a complex inositol polyphosphate response with rapid increases not only in inositol 1,4,5-trisphosphate and inositol 1,3,4,5-tetrakisphosphate, but also in D/L-inositol 1,4,5,6-tetrakisphosphate, inositol 1,3,4,5,6-pentakisphosphate, and inositol hexakisphosphate after co-cross-linking of CD4 and Fc gamma R. In conclusion, co-cross-linking of CD4 and Fc gamma R, which may occur in vivo during HIV infection or treatment with therapeutic anti-CD4 antibodies, appears to be a strong activation mechanism for the inositol polyphosphate/Ca2+ signal transduction pathway in U937 cells.

Antigens, Differentiation↗
PubMed1992

Effects of CD4 synthetic peptides on HIV type I envelope glycoprotein function.

Benzylated derivatives of a peptide (CD4(81-92)) representing the CDR3-like region of CD4 were previously found to inhibit gp120 binding, HIV-1 infectivity, and syncytium formation. These results have been interpreted to indicate a role for the corresponding CD4 region in these processes. The peptide (TbYICbEbVEDQKAcEE) is the prototype of a series of similar CD4(81-92) derivatives. We report that this peptide noncompetitively inhibits binding to CD4 of both gp120 and a mAb (MAX.16H5), both of which recognize the CDR2-like region of CD4. The binding of an antibody (Leu 3a) that is directed against a different area of the D1 domain of CD4 was also inhibited. The peptide derivative inhibited both HIV-1- and HTLV-1-mediated syncytium formation in the same concentration range. Nonbenzylated cyclic and linear peptides representing the CDR3-like region of CD4 (CD4(84-101)) had only minor effects on gp120 binding which were not sequence specific. The results of this study suggest that the effects of benzylated CD4(81-92) derivatives on HIV-1 binding or fusion should not be used to reach conclusions about the function of the corresponding CD4 region.

Binding Sites↗
PubMed1992

Determination of inositol polyphosphates from human T-lymphocyte cell lines by anion-exchange high-performance liquid chromatography and post-column derivatization.

The intracellular amounts of several inositol tris-, tetrakis- and pentakisphosphates and inositol hexakisphosphate were determined in resting and stimulated cells from human T-lymphocyte lines. The inositol polyphosphates were separated by anion-exchange high-performance liquid chromatography and were detected on-line by a recently developed post-column dye system. In the human T-lymphocyte cell line Jurkat, basal intracellular concentrations ranged between 25 +/- 10 pmol per 10(9) cells for inositol 1,4,5-trisphosphate to 6380 +/- 355 pmol per 10(9) cells for inositol hexakisphosphate. Similar basal concentrations were observed in the human T-lymphocyte cell line HPB.ALL, with the exception that inositol hexakisphosphate was approximately 665 +/- 10 pmol per 10(9) cells. Stimulation of the human T-lymphocyte cell line Jurkat via the T-cell receptor by a monoclonal antibody directed against the T-cell receptor-CD3 complex induced time-dependent changes in the intracellular concentrations of multiple inositol polyphosphate isomers, including inositol 1,3,4-trisphosphate, inositol 1,3,4,5-tetrakisphosphate, inositol 1,3,4,6-tetrakisphosphate, an as yet unidentified inositol tetrakisphosphate isomer, inositol 1,3,4,5,6-pentakisphosphate, inositol 1,2,3,4,6-pentakisphosphate and DL-inositol 1,2,4,5,6-pentakisphosphate. Inositol 1,4,5-trisphosphate increased only transiently after 5 min, whereas DL-inositol 1,4,5,6-tetrakisphosphate (determined as the enantiomeric mixture) increased after 20 min.

Anions↗
PubMed1992

Specificity and T cell receptor beta chain usage of a human collagen type II-reactive T cell clone derived from a healthy individual.

Collagen type II (CII) is a cartilage-specific matrix compound well known as an inducer of an experimental, T cell-dependent autoimmune arthritis, a disease which shows some similarities to human rheumatoid arthritis. Here we report on an HLA-DR7-restricted human CD4 T cell clone (TC9), which was isolated from a healthy donor and recognizes human CII. After screening CNBr fragments of CII and tryptic fragments derived thereof, the T cell epitope could be mapped to amino acid residues 271-285 of the triple helical region of CII that are located within CNBr fragment 11 [alpha 1 (II) CB11]. This epitope was confirmed by a synthetic peptide stimulatory for TC9. The T cell receptor beta chain of TC9 was cloned using the polymerase chain reaction; it comprises V beta 6.7 and contains besides J beta 2.3 and C beta 2 an as yet undescribed sequence for the D segment.

Adult↗
PubMed1992

Antibody binding to a collagen type-II epitope gives rise to an inhibitory peptide for autoreactive T cells.

It is well documented that antigen recognition by T cells requires small peptides which are generated by protein cleavage in antigen-presenting cells. These peptides have to associate with major histocompatibility complex (MHC) molecules in order to be recognized. An inhibitory peptide may bind to the same site of the MHC-encoded protein but is not recognized by the T cell. Here we describe a stimulatory and an inhibitory peptide sequence within human collagen type II (CII) as defined by means of the same autoreactive human T cell clone. Most interestingly, the inhibitory peptide is not generated by regular processing in peripheral blood mononuclear cells but only in the presence of an antibody that binds to the same domain and thereby seems to protect the inhibitory sequence. This finding may indicate that certain autoantibodies have the potential to block autoreactive T cells with specificity for a distinct epitope on the same antigen.

Amino Acid Sequence↗
PubMed1992

Inhibition of the anti-CD3-induced T cell proliferation by crosslinking of stimulatory antibodies in the presence of PMA and interleukin-2.

Anti-CD3 antibodies are directed to the nonpolymorphic part of the T cell receptor complex and may activate human peripheral T cells. Under some circumstances crosslinked anti-CD3 has been described to augment the proliferative response. Here we demonstrate that crosslinking of stimulatory anti-CD3 antibodies by anti-IgG in cell suspension abolishes their effect on proliferation of human resting peripheral T cells in the presence of PMA and/or IL-2. This effect was observed within a wide range of anti-CD3 concentrations (1 ng/ml to 1 microgram/ml) independent of the presence of monocytes. The inhibition was not due to the induction of cell death, since cells remained propidium iodide-negative after treatment. Protein-tyrosine phosphorylation after anti-CD3 crosslinking was more pronounced than in the presence of noncrosslinked anti-CD3. This indicates that the signal was transmitted after anti-CD3 crosslinking, however, it was unable to induce T cell proliferation. Reduced IL-2 receptor expression after anti-CD3 crosslinking and the inability of exogenous IL-2 to restore the proliferative response might indicate a reduced susceptibility to IL-2 as a reason for the described phenomenon.

Cell Death↗
PubMed1992

Suppression of antibody responses in rats to murine anti-CD4 monoclonal antibodies by conjugates with monomethoxypolyethylene glycol.

The effectiveness of therapeutically relevant xenogeneic monoclonal antibodies (MoAb) may be counteracted by their inherent immunogenicity. Since conjugates of diverse proteins with mono-methoxypolyethylene glycol (mPEG) were shown to induce Ag-specific tolerance in mice and rats, we used outbred rats in this study as an experimental model for establishing the tolerogenicity of mPEG conjugates of murine MoAb. The results demonstrate that: (i) murine anti-rat CD4 MoAb (W3/25) were more immunogenic than murine anti-human CD4 MoAb (MAX.16H5) in rats; (ii) W3/25 preferentially induced an anti-idiotypic (anti-id) antibody response; and (iii) antibodies to both common and idiotypic determinants could be suppressed in rats by treatment with W3/25(mPEG)28.

Animals↗