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Biomedical subjects

C D Benjamin

Publications and source records attributed to C D Benjamin.

36 records · Page 2Linked to original sources
PubMed1994

Alpha 4-integrins mediate antigen-induced late bronchial responses and prolonged airway hyperresponsiveness in sheep.

Eosinophils and T lymphocytes are thought to be involved in allergic airway inflammation. Both cells express the alpha 4 beta 1-integrin, very late antigen-4 (VLA-4, CD49d/CD29); alpha 4-integrins can promote cellular adhesion and activation. Therefore, we examined the in vivo effects of a blocking anti-alpha 4 monoclonal antibody, HP 1/2, on antigen-induced early and late bronchial responses, airway hyperresponsiveness, inflammatory cell influx, and peripheral leukocyte counts in allergic sheep. Sheep blood lymphocytes, monocytes, and eosinophils expressed alpha 4 and bound HP 1/2. In control sheep, Ascaris antigen challenge produced early and late increases in specific lung resistance of 380 +/- 42% and 175 +/- 16% over baseline immediately and 7 h after challenge, respectively, as well as airway hyperresponsiveness continuing for 14 d after antigen challenge. Treatment with HP 1/2 (1 mg/kg, i.v.) 30 min before antigen challenge did not affect the early increase in specific lung resistance but inhibited the late-phase increase at 5-8 h by 75% (P < 0.05) and inhibited the post-antigen-induced airway hyperresponsiveness at 1, 2, 7, and 14 d (P < 0.05, for each time). Intravenous HP 1/2 given 2 h after antigen challenge likewise blocked late-phase airway changes and postchallenge airway hyperresponsiveness. Airway administration of HP 1/2 (16-mg dose) was also effective in blocking these antigen-induced changes. Response to HP 1/2 was specific since an isotypic monoclonal antibody, 1E6, was ineffective by intravenous and aerosol administration. Inhibition of leukocyte recruitment did not totally account for the activity of anti-alpha 4 antibody since HP 1/2 neither diminished the eosinopenia or lymphopenia that followed antigen challenge nor consistently altered the composition of leukocytes recovered by bronchoalveolar lavage. Because airway administration of HP 1/2 was also active, HP 1/2 may have inhibited cell activation. Reduction of platelet-activating factor-induced eosinophil peroxidase release from HP 1/2-treated eosinophils supports such a mechanism. These findings indicate a role for alpha 4-integrins in processes that lead to airway late phase responses and persisting airway hyperresponsiveness after antigen challenge.

Aerosols↗
PubMed1993

Stimulation of protein tyrosine phosphorylation in human B cells after ligation of the beta 1 integrin VLA-4.

B lymphocytes express several adhesion molecules that are involved in cell-cell and cell-extracellular matrix interactions. The alpha 4 beta 1 integrin VLA-4, expressed on pre-B and mature/activated B cells, mediates adhesion of these cells to its two ligands, VCAM-1 and fibronectin. Recent evidence suggests that VLA-4 is involved in T lymphocyte activation; however, relatively little is known of the role of VLA-4 in B cell differentiation. To begin to assess the potential involvement of VLA-4 in B cell activation, we have examined the effect of ligation of VLA-4 on protein tyrosine phosphorylation in B cells. We found that cross-linking of VLA-4 by either mAb or natural ligands (i.e., VCAM-1 and the FN-40 cleavage fragment of fibronectin) induced the tyrosine phosphorylation of a 110-kDa protein in a human pre-B cell line (Nalm-6), an EBV-transformed B cell line (SB), and normal tonsillar B cells. These findings suggest that VLA-4 can activate a tyrosine kinase in B cells and B cell lines. These signals may be involved in the subsequent differentiation of pre-B and mature B cells within specific microenvironments where VLA-4 mediated adhesion is operational.

Antigens, CD↗
PubMed1993

Expression of vascular cell adhesion molecule-1 in kidney allograft rejection.

VCAM-1, a leukocyte adhesion molecule expressed by cytokine-activated endothelial cells in culture, may mediate mononuclear leukocyte infiltration in vessels and interstitium in solid organ allograft rejection. Using the avidin-biotin immunoperoxidase technique and an affinity-purified rabbit polyclonal antisera to recombinant human VCAM (rVCAM Ab) which works in methyl Carnoy's fixed tissues, we studied the expression of this molecule in biopsies of transplanted kidneys (N = 34) with and without features of rejection and allograft nephrectomies (N = 17) as well as nontransplanted control tissues (N = 26). The rVCAM Ab showed a population of reactive endothelial cells limited to sites of prominent subendothelial leukocytic cell infiltration in arteries and veins, and occasional peritubular capillaries (PTC) in rejecting allografts. Endothelial expression of VCAM was rarely identified in biopsies showing interstitial rejection only or cyclosporine toxicity, usually in PTC, and was only rarely encountered in nontransplanted control tissues. Apparent de novo expression of VCAM-1 by arterial smooth muscle cells and mesangial cells was present in cases of severe rejection. In addition, a population of cells (DC) with dendritic morphology was identified by rVCAM Ab within sites of lymphoid cell aggregation in rejecting allografts. Further evidence that these cells represent true DC was obtained by identification of VCAM-1 positive, morphologically similar cells in both germinal centers and interfollicular areas of all seven reactive lymph nodes tested; and by similar staining of these cells in the allografts and lymph nodes by antibodies to nerve growth factor receptor and the complement receptor CR1, previously shown to recognize DC. DCs were generally not seen in uninflamed normal control organs or portions of allografts uninvolved by lymphoid aggregates. Enhanced tubular epithelial cell expression of VCAM-1 was also present in rejecting allografts. All staining could be abolished by absorption of the antisera with VCAM-1 transfected, but not ICAM-1 or ELAM-1 transfected, CHO cells. In situ hybridization studies utilizing a cDNA probe to human VCAM-1 demonstrated mRNA production by glomerular, tubular and vascular cells corresponding to sites where the protein was immunohistochemically localized.(ABSTRACT TRUNCATED AT 400 WORDS)

Arteries↗
PubMed1993

Attenuation of colitis in the cotton-top tamarin by anti-alpha 4 integrin monoclonal antibody.

Recent studies have demonstrated the induced expression of endothelial adhesion molecules including E-selectin (also called endothelial leukocyte adhesion molecule-1), vascular cell adhesion molecule and intercellular adhesion molecule in actively involved mucosa of patients with ulcerative colitis and Crohn's disease. Similar induction has been demonstrated in the colon of the Cotton-top tamarin (CTT), a New World primate that experiences a spontaneous acute and chronic colitis resembling ulcerative colitis. To assess the potential importance of leukocyte adhesion as a necessary step in acute colitis, the effect of parenteral mAb directed against adhesion molecules on CTT colitis was evaluated in placebo-controlled blinded trials. Serial administration of either of two anti-E-selectin mAb designated BB11 and EH8 effectively coated endothelial surfaces expressing this vascular adhesion molecule. Although colitis activity was slightly diminished after the 10-d treatment period in CTT receiving either BB11 or EH8, this reduction was not significantly different than that seen in animals given a placebo control when assessed by a previously validated standardized scale of inflammatory activity: mean histologic activity grade 2.2 +/- 0.2 pretreatment vs 1.5 +/- 0.5 posttreatment in group receiving mAb and 2.1 +/- 0.1 pretreatment vs 1.3 +/- 0.5 posttreatment in the placebo group (P > 0.2). In contrast, administration of an anti-alpha 4 integrin mAb designated HP1/2 that binds VLA4 (alpha 4 beta 1) and presumably alpha 4 beta 7 integrins resulted in significant attenuation of acute colitis when compared to both pretreatment activity index (P = 0.005) and the placebo control group (P < 0.01): mean histologic activity grade 1.6 +/- 0.3 pretreatment vs 0.2 +/- 0.1 posttreatment in the group receiving HP1/2 and 1.8 +/- 0.5 pretreatment and 1.2 +/- 0.2 posttreatment in the placebo control group. These studies using a model of spontaneous colitis in the CTT demonstrate the feasibility of modulation of leukocyte-vascular adhesion and/or other integrin-mediated events possibly including T cell aggregation and T cell-stromal interactions, as well as lymphocyte homing. These results suggest both that these processes are important and possibly essential elements in sustaining acute colitis and that their disruption may result in therapeutic benefit.

Animals↗
PubMed1993

Vascular cell adhesion molecule-1 is expressed in human coronary atherosclerotic plaques. Implications for the mode of progression of advanced coronary atherosclerosis.

Endothelial attachment is the initial step in leukocyte recruitment into developing atherosclerotic lesions. To determine whether vascular cell adhesion molecule-1 (VCAM-1) expression may play a role in inflammatory cell recruitment into human atherosclerotic lesions, immunohistochemistry was performed with a polyclonal rabbit antisera, raised against recombinant human VCAM-1, on 24 atherosclerotic coronary plaques and 11 control coronary segments with nonatherosclerotic diffuse intimal thickening from 10 patients. Immunophenotyping was performed on adjacent sections to identify smooth muscle cells, macrophages, and endothelial cells. To confirm VCAM-1-expressing cell types, double immunostaining with VCAM-1 antisera and each of the cell-specific markers and in situ hybridization were performed. All atherosclerotic plaques contained some VCAM-1, compared to 45% of control segments. VCAM-1 was found infrequently on endothelial cells at the arterial lumen din both plaques (21%) and in control segments (27%), but was prevalent in areas of neovascularization and inflammatory infiltrate in the base of plaques. Double immunostaining and in situ hybridization confirmed that most VCAM-1 was expressed by subsets of plaque smooth muscle cells and macrophages. The results document the presence of VCAM-1 in human atherosclerosis, demonstrate VCAM-1 expression by human smooth muscle cells in vivo, and suggest that intimal neovasculature may be an important site of inflammatory cell recruitment into advanced coronary lesions.

Animals↗
PubMed1993

Expression of vascular cell adhesion molecule (VCAM-1) in liver and pancreas allograft rejection.

VCAM-1, a leukocyte adhesion molecule expressed by cytokine-activated endothelial cells in culture, may mediate mononuclear leukocyte infiltration in vessels and interstitium in solid organ allograft rejection. Using the avidin-biotin immunoperoxidase technique and two different antibodies--4B9, a murine monoclonal antibody, and rabbit polyclonal antisera to recombinant human VCAM (rVCAM Ab), which work in methacarn-fixed tissues--we studied the expression of this molecule in biopsies of transplanted liver and pancreas with and without features of rejection as well as nontransplant control tissues. The rVCAM Ab, but not 4B9, showed a population of reactive endothelial cells limited to sites of prominent subendothelial leukocytic cell infiltration in arteries and veins in rejecting allografts. VCAM-1 expression by sinusoidal endothelium in rejecting liver allografts was also observed. In addition, a population of cells (DC) with dendritic morphology was identified by rVCAM Ab within sites of lymphoid cell aggregations in both liver and pancreas allografts. Further evidence that these cells represent true DC was obtained by identification of VCAM-1 positive morphologically similar cells in both germinal centers and interfollicular areas of reactive lymph nodes; and by similar staining of these cells in allograft organs by a monoclonal antibody to nerve growth factor receptor, previously shown to recognize DC. DCs were generally not seen in normal control organs or portions of allografts uninvolved by lymphoid aggregates. This study provides evidence that 1) endothelial cell expression of VCAM-1 may be important in transplant rejection, 2) different epitopes of VCAM-1 may be preserved in tissue sections and recognized by different antibodies, and 3) there is probably a population of VCAM-1 expressing DC that participates in the cellular rejection progress.

Antibodies, Monoclonal↗
PubMed1992

Activated endothelium binds lymphocytes through a novel binding site in the alternately spliced domain of vascular cell adhesion molecule-1.

Vascular cell adhesion molecule-1 (VCAM-1) is induced on endothelial cells by inflammatory cytokines, and binds mononuclear leukocytes through the integrin very late antigen-4 (VLA-4) (alpha 4 beta 1). This adhesion pathway has been implicated in a diverse group of physiological and pathological processes, including B cell development, leukocyte activation and recruitment to sites of inflammation, atherosclerosis, and tumor cell metastasis. The major form of VCAM-1 (VCAM-7D) has seven extracellular immunoglobulin (Ig)-like domains, of which the three NH2-terminal domains (domains 1-3) are similar in amino acid sequence to domains 4-6. By functional analysis of VCAM-7D relative to VCAM-6D (a minor 6-domain form of VCAM-1 in which domain 4 is deleted because of alternative splicing), and chimeric constructs between VCAM-1 and its structural relative intercellular adhesion molecule-1 (ICAM-1), we show that either the first or the homologous fourth domain of VCAM-1 is required for VLA-4-dependent adhesion. Either of these binding sites can function in the absence of the other. When both are present, cell binding activity is increased relative to monovalent forms of the molecule. The homologous binding regions appear to have originated by internal duplication of a portion of a monovalent ancestral gene, before the mammalian radiation. Thus VCAM-1 exemplifies evolution of a functionally bivalent cell-cell adhesion molecule by intergenic duplication. We have also produced a new class of anti-VCAM-1 monoclonal antibodies that block domain 4-dependent adhesion, and demonstrate that both binding sites participate in the adhesion function of VCAM-1 on endothelial cells in vitro. Therefore both sites must be blocked in clinical, animal, or in vitro studies depending on the use of anti-VCAM-1 antibodies to inactivate the VCAM-1/VLA-4 adhesion pathway.

Amino Acid Sequence↗
PubMed1992

E-selectin (endothelial-leukocyte adhesion molecule-1) is not required for the migration of neutrophils across IL-1-stimulated endothelium in vitro.

Treatment of vascular endothelial cells with inflammatory cytokines stimulates surface expression of E-selectin (previously known as endothelial-leukocyte adhesion molecule-1) and promotes the transendothelial migration of neutrophils. To assess participation of E-selectin in cytokine-mediated neutrophil migration, an in vitro model consisting of monolayers of human umbilical vein endothelial cells (HUVEC) grown on amniotic connective tissue was used. When HUVEC-amnion cultures were stimulated for 4 h with relatively low concentrations of IL-1 (0.1 to 0.15 U/ml), mAb BB11 or H18/7 to E-selectin partially inhibited migration of subsequently added neutrophils. However, when the cultures were stimulated with 15 U/ml of IL-1 for 4 or 24 h, little to no inhibition was observed. mAb to E-selectin also failed to inhibit migration of neutrophils across HUVEC-amnion cultures treated with low doses of IL-1 when the leukocytes were additionally stimulated by the chemoattractant leukotriene B4. In contrast, migration of neutrophils across IL-1-treated HUVEC was profoundly inhibited by mAb to CD11/CD18 leukocytic integrins under all conditions tested. Results of these studies suggest that participation of E-selectin is not essential for migration of neutrophils across cytokine-stimulated HUVEC in vitro; rather, E-selectin can be bypassed in favor of CD11/CD18-dependent mechanisms under appropriate circumstances.

Antibodies, Monoclonal↗
PubMed1991

Expression and functional characterization of a soluble form of endothelial-leukocyte adhesion molecule 1.

Endothelial leukocyte adhesion molecule 1 (ELAM1) is a leukocyte adhesion molecule induced on human venular endothelium in vitro and in vivo by inflammatory stimuli. A truncated cDNA for ELAM1 has been constructed, stably expressed in Chinese hamster ovary cells, and the secreted recombinant soluble form of ELAM1 (rsELAM1) purified to homogeneity by immunoaffinity chromatography. rsELAM1, when immobilized on plastic, is fully functional as an adhesion protein, and selectively binds only cells known to bind cell-surface ELAM1 expressed on human endothelial cells, including the myelomonocytic cell line HL60 and the colon carcinoma cell line HT29. Immobilized rsELAM1 also binds human PMN, monocytes, NK cells, and T cells. T cell subset analyses indicate preferential binding of CD4+ T memory cells. However, rsELAM1 is only a weak inhibitor of ELAM1-mediated adhesion. rsELAM1 should prove valuable for the further study of the role of ELAM1 expressed on the vascular wall during the inflammatory response.

Amino Acid Sequence↗
PubMed1984

Immunodominant protein epitopes. II. The primary antibody response to hen egg white lysozyme requires and focuses upon a unique N-terminal epitope.

The antibody response to a defined protein antigen, hen egg white lysozyme (HEL) has been investigated using an aminopeptidase-treated HEL molecule, des-1,2,3-HEL (AP-HEL). Surprisingly, removal of these three N-terminal residues eliminates an epitope which is a dominant B cell determinant recognized in the primary antibody response to HEL. Thus, the initial antibody response focuses on a very small region of the molecule. Even more striking is the observation that removal of this epitope markedly reduces the immunogenicity of HEL. Therefore, the epitope is not only the focus of the primary antibody response, but is essential for the initiation of the response. This report demonstrates that a selective mechanism must be activated during the response to this protein antigen. Of the multitude of B cell determinants present on HEL, only a limited number are focused upon by the immune system.

Amino Acid Sequence↗
PubMed1980

A predominant idiotype on anti-hen egg white lysozyme antibodies from diverse mouses strains.

A predominant idiotype was detected on almost all antibody molecules directed against the multideterminant antigen, hen egg white lysozyme (HEL). This idiotypic set was defined by rabbit and quinea pig antiidiotypic antisera raised against a rare cross-reactive antibody population isolated and from a heterogeneous BALB/c anti-human lysozyme (HUL) humoral response. This isiotype was fond on the majority of all HEL-reactive antibody from all strain tested; its presence was independent of Ig-1 allotype of H-2 haplotype. The idiotype was also present on the majority of anti-HEL antibody from nonresponder mice immunized with keyhole limpet hemocyanin coupled to HEL. The idiotype was not found on normal mouse immunoglobulin or on antibodies specific to two other proteins, HUL and ribonuclease, which are similar to HEl in size and charge. Individual idiotype-positive anti-HEL antibody populations exhibited specificity differences when analyzed for reactivity toward other avian lysozymes, suggesting that distinct clonal products shared the idiotype specificities. Fractionation of heterogeneous anti-HEL antibodies by preparative isoelectric focusing yielded distinct antibody fractions that were demonstrated to share the relevant idiotype determinants. The data are discussed in terms of the HEL peptide specificites of idiotype-positive and -negative antibodies.

Animals↗