Biomedical subjects

T F Tedder

Publications and source records attributed to T F Tedder.

At least 91 records · Page 5Linked to original sources

PubMed1996

L- and P-selectins, but not CD49d (VLA-4) integrins, mediate monocyte initial attachment to TNF-alpha-activated vascular endothelium under flow in vitro.

Monocyte adhesion to the vascular endothelium is a pivotal step during their egress to tissues at sites of inflammation and immune reactions, and during atherogenesis. In this study, an in vitro flow model and blocking mAb were used to define the role of adhesion molecules in monocyte interactions with activated HUVEC under flow conditions. By videomicroscopy, freely flowing monocytes abruptly halted (initial attachment) on 6-h TNF-alpha-activated HUVEC under flow via L- and P-selectin, whereas E-selectin was not involved. CD49d/CD29 integrin (VLA-4), which can mediate initial attachment of certain T cells to VCAM-1 under flow, did not support monocyte initial attachment. Once initially attached, a small number of monocytes began rolling at 9 microns/s through a mechanism involving L-selectin, as well as CD49d and CD11/CD18 integrins, while the remaining monocytes became firmly adherent, or released to the flow stream. Monocyte stable arrest and subsequent transendothelial migration occurred rapidly and efficiently through either CD49d or CD18 integrin adhesion pathways. Transendothelial passage was also dependent on PECAM-1 (CD31). These data reveal monocytes initially attach to activated endothelium via an L-selectin-dependent mechanism, with a smaller contribution from P-selectin and no contribution by CD49d. Subsequent monocyte rolling, arrest, and transmigration require overlapping functions between multiple members of the selectin, integrin, and Ig gene families.

Animals↗

PubMed1996

Engagement of the adhesion receptor CD22 triggers a potent stimulatory signal for B cells and blocking CD22/CD22L interactions impairs T-cell proliferation.

The B-lymphocyte-restricted adhesion protein CD22 mediates sialic acid-dependent cell-cell interactions. Engagement of CD22 on B lymphocytes with a CD22 monoclonal antibody (MoAb) HB22.7 that blocks the binding of CD22 to its ligand(s) directly stimulated B-cell proliferation. In addition, the HB22.7 MoAb costimulated B-cell proliferation with either anti-IgM, interleukin-2 (IL-2), IL-4, or CD40 and triggered predominantly B-cell IgG secretion with IL-2. Even more striking levels of B-cell proliferation occurred with HB22.7 MoAb under culture conditions that enhanced B-B-cell interactions. In contrast, a nonblocking CD22 MoAb (CD22.5) poorly costimulated in similar experiments. The functional differences between the two antibodies likely result from differing abilities to trigger downstream signaling events as significant differences in CD22 tyrosine phosphorylation and the recruitment of the tyrosine kinase p53/56lyn and the tyrosine phosphatase SH-PTP1C were found. Besides their role in B-cell stimulation, CD22/CD22L interactions may also assist in regulating T-cell proliferation because inhibition of CD22-CD22L engagement with the HB22.7 MoAb impaired T-cell proliferation in a costimulatory assay. Thus, CD22/CD22L interactions result in stimulatory signals for both B and T lymphocytes.

Amino Acid Sequence↗

PubMed1996

CD14+ blood monocytes can differentiate into functionally mature CD83+ dendritic cells.

Dendritic cells are potent antigen-presenting cells that initiate primary immune responses. Although dendritic cells derive from bone marrow stem cells, the intermediate stages in their development remain unknown. In this study, plastic-adherent blood monocytes (CD14+, CD1a-) cultured for 7 days with granulocyte-monocyte colony-stimulating factor, interleukin 4, and tumor necrosis factor alpha were shown to differentiate into CD1a+ CD83+ dendritic cells. These cells displayed all phenotypic and morphologic characteristics of mature dendritic cells and were the most potent stimulatory cells in allogeneic mixed leukocyte reactions. The identification of specific culture conditions that generate large numbers of dendritic cells from purified monocytes uncovers an important step in dendritic cell maturation that will allow the further characterization of their role in autoimmune diseases, graft rejection, and human immunodeficiency virus infection.

Adult↗

PubMed1996

Involvement of p72syk kinase, p53/56lyn kinase and phosphatidyl inositol-3 kinase in signal transduction via the human B lymphocyte antigen CD22.

CD22 is a B lymphocyte-specific membrane protein that functions as an adhesion molecule via its interactions with a subset of alpha 2-6-linked sialic acid-containing glycoproteins. Engagement of CD22 with a monoclonal antibody (HB22.23) that blocks the binding of CD22 to its ligands results in rapid CD22 tyrosine phosphorylation and in increased association of CD22 with p53/56lyn kinase, p85 phosphatidyl inositol-3 kinase, and p72syk kinase. Synthetic peptides that span various regions of the intracellular portion of CD22 were used to map potential kinase binding sites. All three kinases associated with a tyrosine-phosphorylated peptide that spans tyrosine amino acid residues 822 and 842, implicating this as an important region in mediating CD22 signal transduction. In addition, purified p56lyn directly bound to the same peptide. Engagement of CD22 with HB22.23 was sufficient to stimulate normal B cell proliferation. This study further substantiates the importance of CD22 as a B lymphocyte signaling molecule and begins to unravel the mechanisms by which CD22 cross-linking can alter B cell function.

Amino Acid Sequence↗

PubMed1996

CD22 is both a positive and negative regulator of B lymphocyte antigen receptor signal transduction: altered signaling in CD22-deficient mice.

B cell activation following antigen receptor cross-linking can be augmented in vitro by ligation of cell surface CD22, which associates with the SHP1 protein tyrosine phosphatase. The targeted deletion of CD22 in mice demonstrated that CD22 differentially regulates antigen receptor signaling in resting and antigen-stimulated B lymphocytes. B cells from CD22-deficient mice exhibited the cell surface phenotype and augmented intracellular calcium responses characteristic of chronically stimulated B cells, as occurs in SHP1-defective mice. Thus, CD22 negatively regulates antigen receptor signaling in the absence of antigen. However, activation of CD22-deficient B lymphocytes by prolonged IgM cross-linking resulted in modest B cell proliferation, demonstrating that CD22 positively regulates antigen receptor signaling in the presence of antigen.

Animals↗

PubMed1996

Differential regulation of leucocyte L-selectin (CD62L) expression in normal lymphoid and inflamed extralymphoid tissues.

AIMS: To study tissue expression of L-selectin, a leucocyte cell surface molecule that is considered to be involved in adhesion to certain endothelia, particularly in peripheral lymph nodes and during inflammation, and is shed upon leucocyte activation. METHODS: Leucocytes were examined by immunohistochemistry and double immunofluorescence staining in various lymphoid sites and normal and inflamed extralymphoid tissues. RESULTS: L-selectin was present on mantle zone B lymphocytes in different lymphoid sites, including in intestinal lymphoid tissue, but was absent on germinal centre B cells. Splenic white pulp B cells also expressed L-selectin. The proportion of T lymphocytes expressing L-selectin depended on the site under study, being greatest in peripheral lymph nodes (mean 48% of T cells positive), and lower in mucosal lymphoid sites and spleen (9 and 11% positive, respectively). Non-lymphocytic L-selectin staining was observed on follicular dendritic cells in tonsils and on macrophages in thymus. L-selectin positive leucocytes were rare in normal extralymphoid tissues, and relatively few were seen in most inflammatory settings. However, in rejecting renal transplants, a higher proportion (30%) of leucocytes expressed L-selectin. CONCLUSIONS: Overall, the results indicate how the degree of L-selectin expression by leucocytes in particular tissues may reflect a requirement for L-selectin expression for entry into those tissues and the activation state of leucocytes once localised there.

Appendicitis↗

PubMed1996

Blocking L-selectin function attenuates reperfusion injury following hemorrhagic shock in rabbits.

Leukocyte adhesion molecule (LAM) blockade reduces ischemia-reperfusion injury. We tested the hypothesis that a monoclonal antibody (MAb) that recognizes a functional epitope of L-selectin would decrease hemorrhagic shock-induced reperfusion injury. Anesthetized rabbits were subjected to 2 h of hemorrhagic shock (cardiac output reduced to 30% of baseline), then given one of the following treatments: MAbs that recognize functional domains of L-selectin (LAM1-3), CD18 (60.3), MAbs that recognize a nonfunctional domain on L-selectin (LAM1-14), or saline, immediately before resuscitation with shed blood. Additional fluids were administered as needed to maintain cardiac output at baseline levels for 6 h. The cumulative fluid resuscitation after MAb LAM1-3 (58 +/- 34 ml/kg) was not significantly different from after MAb 60.3 (21 +/- 24 ml/kg) or MAb LAM1-14 (66 +/- 51 ml/kg), but it was significantly less than saline-treated controls (142 +/- 142 ml/kg). However, two animals treated with MAb LAM1-14 died before 6 h. If their resuscitation volumes are projected to 6 h by linear regression, then the LAM1-14-treated group required significantly greater volume (101 +/- 99 ml/kg) than the MAb LAM1-3-treated group. We conclude that MAbs to a functional domain on L-selectin are protective against reperfusion-injury following hemorrhagic shock.

Animals↗

PubMed1996

Velocity differences between L- and P-selectin-dependent neutrophil rolling in venules of mouse cremaster muscle in vivo.

After surgical trauma, leukocyte rolling is initially normal in L-selectin-deficient mice and reduced at later times, whereas leukocyte rolling is initially absent in P-selectin-deficient mice but induced later. Here, we examined the possibility that P- and L-selectin support rolling at different characteristic velocities using intravital microscopy of venules of the exteriorized cremaster muscle venules of wild type (WT) and P- and L-selectin-deficient mice. At > 50 min after exteriorization, rolling in P-selectin-deficient mice occurred at significantly higher velocities (129 +/- 89 microns/s) than in WT mice (49 +/- 23 microns/s). Rolling velocity distribution in L-selectin-deficient mice was similar to WT mice immediately after exteriorization. Histological examination of Giemsa-stained whole-mount preparations in cremaster muscle venules revealed that the majority of rolling cells (approximately 90% in all genotypes) were granulocytes. We conclude that P-selectin mediates leukocyte rolling at velocities < 50 microns/s, whereas L-selectin sustains more rapid rolling. Under physiological conditions, P- and L-selectin synergize to support rolling at velocities between 20 and 70 microns/s as seen in WT mice.

Abdominal Muscles↗

PubMed1995

The CD19 signal transduction molecule is a response regulator of B-lymphocyte differentiation.

The phenotypes of CD19-deficient (CD19-/-) mice, and human CD19-transgenic (hCD19TG) mice that overexpress CD19 indicate that CD19 is a response regulator of B-lymphocyte surface receptor signaling. To further characterize the function of CD19 during B-cell differentiation, humoral immune responses to a T-cell-independent type 1 [trinitrophenyl-lipopolysaccharide (TNP-LPS)], a T-cell-independent type 2 [dinitrophenyl (DNP)-Ficoll], and a T-cell-dependent [DNP-keyhole limpet hemocyanin (KLH)] antigen were assessed in CD19-/- and hCD19TG mice. B cells from CD19-/- mice differentiated and underwent immunoglobulin isotype switching in vitro in response to mitogens and cytokines. In vivo, CD19-/- mice generated humoral responses to TNP-LPS and DNP-KLH that were dramatically lower than those of wild-type littermates. Surprisingly, the humoral response to DNP-Ficoll was significantly greater in CD19-/- mice. In contrast, hCD19TG mice were hyperresponsive to TNP-LPS and DNP-KLH immunization but were hyporesponsive to DNP-Ficoll. These results demonstrate that CD19 is not required for B-cell differentiation and isotype switching but serves as a response regulator which modulates B-cell differentiation. Since humoral responses to both T-cell-dependent and T-cell-independent antigens were similarly affected by alterations in CD19 expression, these differences are most likely to result from intrinsic changes in B-cell function rather than from the selective disruption of B-cell interactions with T cells.

Animals↗

PubMed1995

A distinct pattern of cytokine gene expression by human CD83+ blood dendritic cells.

Dendritic cells are the most potent antigen-presenting cells of the immune system. Although dendritic cells are likely to secrete selective cytokines that facilitate antigen presentation, the difficulty in isolating pure dendritic cells in sufficient numbers has made assessment of this function imprecise. In this study, pure populations of CD83+ human blood dendritic cells were isolated by previously established enrichment procedures and subsequent cell sorting. Cytokine gene expression was assessed by reverse transcription-polymerase chain reaction (RT-PCR) amplification of mRNA. Resting CD83+ dendritic cells expressed interleukin-6 (IL-6), IL-8, IL-10, tumor necrosis factor-alpha (TNF-alpha), and transforming growth factor-beta 1 (TGF-beta 1) mRNA, while activation of cells with phorbol myristate acetate induced IL-1 alpha and beta, IL-9, TNF-beta, interferon-gamma, granulocyte-macrophage colony-stimulating factor (GM-CSF), M-CSF, and G-CSF mRNA expression. Resting CD83+ cells also expressed the Rantes, MCP-1, MIP-1 alpha, and MIP-1 beta chemokines, with 1-309 expression induced upon activation. Resting and activated CD83+ dendritic cells also expressed receptors for IL-2 (CD25), TGF-beta 1 and -beta 3, and GM-CSF as determined by indirect immunofluorescence staining. These results indicate that dendritic cells have the ability to produce a variety of soluble factors which are likely to contribute substantially to the potent allostimulatory activity of these cells.

Antigen Presentation↗

PubMed1995

Structural requirements regulate endoproteolytic release of the L-selectin (CD62L) adhesion receptor from the cell surface of leukocytes.

L-selectin mediates leukocyte rolling on vascular endothelium at sites of inflammation and lymphocyte migration to peripheral lymph nodes. L-selectin is rapidly shed from the cell surface after leukocyte activation by a proteolytic mechanism that cleaves the receptor in a membrane proximal extracellular region. This process may allow rapid leukocyte detachment from the endothelial surface before entry into tissues. In this study, the structural requirements for regulation of human L-selectin endoproteolytic release were examined through analysis of chimeric selectin molecules and mutant L-selectin receptors. The use of chimeric selectins and a cytoplasmic tail truncation mutant demonstrated that the extracellular membrane-proximal 15-amino acid region of L-selectin is required for endoproteolytic release. The introduction of alanine-scanning mutations within this membrane-proximal region did not prevent endoproteolytic release, indicating that a specific amino acid motif was not an absolute requirement for cleavage. Furthermore, alterations within the putative primary cleavage site (K283-S284) resulted in either constitutive endoproteolytic release of the receptor or inhibition of cell activation-induced shedding to variable extents. The length of the membrane-proximal region was also critical since truncations of this region completely abolished endoproteolytic release. Thus, release of L-selectin is likely to be regulated by the generation of an appropriate tertiary conformation within the membrane-proximal region of the receptor which allows recognition by a membrane-bound endoprotease with relaxed sequence specificity that cleaves the receptor at a specific distance from the plasma membrane. These observations suggest a generalized protein-processing pathway involved in the endoproteolytic release of specific transmembrane proteins which harbor widely differing primary sequences at or neighboring their cleavage sites.

Amino Acid Sequence↗

PubMed1995

Leukocyte interactions with vascular endothelium. New insights into selectin-mediated attachment and rolling.

Among the earliest signs of inflammation is the capture of leukocytes from the blood stream and their subsequent rolling along the endothelium of postcapillary venules. This commentary summarizes recent insight into the molecular basis of leukocyte rolling gained from gene-targeted mice, Ab blocking studies, and in vitro and in vivo reconstitution assays. These data reveal how the selectins individually and collectively contribute to the process of leukocyte capture and subsequent rolling on vascular endothelium.

Animals↗

PubMed1995

L-selectin-deficient mice have impaired leukocyte recruitment into inflammatory sites.

L-selectin, a cell surface adhesion molecule that is expressed by most leukocytes, mediates leukocyte rolling along vascular endothelium at sites of inflammation. The contribution of L-selectin to leukocyte migration in models of chronic inflammation was assessed by using mice that lack cell surface L-selectin expression. Significant inhibition of neutrophil (56-62%), lymphocyte (70-75%), and monocyte (72-78%) migration into an inflamed peritoneum was observed 24 and 48 h after administration of thioglycollate, an inflammatory stimulus. L-selectin-deficient mice were also significantly impaired in delayed-type hypersensitivity reactions. Footpad swelling in response to sheep red blood cell challenge was reduced 75% in L-selectin-deficient mice compared with wild-type mice. Ear swelling in a model of contact hypersensitivity induced by oxazolone challenge was also reduced by 69% compared to wild-type mice. Consistent with L-selectin-mediating leukocyte migration into diverse vascular beds during inflammation, L-selectin-deficient mice were significantly resistant to death resulting from lipopolysaccharide (LPS)-induced toxic shock. LPS administration resulted in a 90% mortality rate in control mice after 24 h, while there was a 90% survival rate in L-selectin-deficient mice. These results demonstrate that L-selectin plays a prominent role in leukocyte homing to nonlymphoid tissues during inflammation and that blocking this process can be beneficial during pathological inflammatory responses.

Animals↗

PubMed1995

Human blood dendritic cells selectively express CD83, a member of the immunoglobulin superfamily.

Dendritic cells are potent APC that initiate primary T cell-dependent immune responses. The lack of lineage-associated cell surface Ags for human dendritic cells has made characterization of this lineage difficult. In this study, analysis of leukocyte subpopulations isolated from human blood revealed that circulating or cultured B and T cells, NK cells, and monocytes did not express CD83, whereas CD83+ cells were predominantly found in the dendritic cell-enriched metrizamide low density fraction of plastic nonadherent blood mononuclear cells. Blood CD83+ cells had a cellular morphology characteristic of dendritic cells and a cell surface phenotype that did not correlate with that of T cells, B cells, NK cells, or cells of the myelomonocytic lineage. Analysis of CD83+ cells with a panel of mAbs that identify 126 leukocyte cell surface Ags revealed the CD83+ cells to be a phenotypically homogeneous and unique population of cells that expressed the highest levels of MHC class II molecules when compared with other leukocyte lineages. CD83+ cells were also the most potent stimulator cells in an allogeneic MLR when compared with other leukocyte lineages. Functional analysis of CD83+ cells revealed that MHC class II, CD11a, CD40 and CD86 played functionally dominant roles, whereas CD80 contributed minimally to the specialized costimulatory activity of these potent APC. Thus, CD83 serves as a useful and specific marker for this unique population of human blood dendritic cells.

Antibodies, Monoclonal↗

PubMed1995

Identification of the ligand-binding domains of CD22, a member of the immunoglobulin superfamily that uniquely binds a sialic acid-dependent ligand.

CD22 is a B cell-restricted member of the immunoglobulin (Ig) superfamily that functions as an adhesion receptor for leukocytes and erythrocytes. CD22 is unique among members of the Ig superfamily in that it has been suggested to bind a series of sialic acid-dependent ligands, potentially through different functional domains expressed by different splice variants of CD22. In this study, the epitopes identified by a large panel of function-blocking and non-function-blocking CD22 monoclonal antibodies were localized to specific Ig-like domains, revealing that all function-blocking monoclonal antibodies bound to the first and/or second Ig-like domains. Consistent with a single ligand-binding region, the two amino-terminal domains were the functional unit that mediated CD22 adhesion with lymphocytes, neutrophils, monocytes, and erythrocytes. The predominant cell surface species of CD22 was a full length 140,000 relative molecular mass seven Ig-like domain glycoprotein and a minor 130,000 relative molecular mass form lacking the fourth domain. While the two amino-terminal Ig-like domains of CD22 are structurally similar to those found in other members of the Ig superfamily involved in cell adhesion and containing an amino acid sequence motif associated with integrin recognition, site-directed mutagenesis of critical residues surrounding this motif did not disrupt CD22-mediated adhesion. These results demonstrate that the unique ligand-binding properties of CD22 are distinct from those of other members of the Ig superfamily involved in integrin-mediated cell adhesion.

Amino Acid Sequence↗

PubMed1995

Sequential contribution of L- and P-selectin to leukocyte rolling in vivo.

Leukocyte recruitment into inflammatory sites is initiated by a reversible transient adhesive contact with the endothelium called leukocyte rolling, which is thought to be mediated by the selectin family of adhesion molecules. Selectin-mediated rolling precedes inflammatory cell emigration, which is significantly impaired in both P- and L-selectin gene-deficient mice. We report here that approximately 13% of all leukocytes passing venules of the cremaster muscle of wild-type mice roll along the endothelium at < 20 min after surgical dissection. Rolling leukocyte flux fraction reaches a maximum of 28% at 40-60 min and returns to 13% at 80-120 min. In P-selectin-deficient mice, rolling is absent initially and reaches 5% at 80-120 min. Rolling flux fraction in L-selectin-deficient mice is similar to wild type initially and declines to 5% at 80-120 min. In both wild-type and L-selectin-deficient mice, initial leukocyte rolling (0-60 min) is completely blocked by the P-selectin monoclonal antibody (mAb) RB40.34, but unaffected by L-selectin mAb MEL-14. Conversely, rolling at later time points (60-120 min) is inhibited by mAb MEL-14 but not by mAb RB40.34. After treatment with tumor necrosis factor (TNF)-alpha for 2 h, approximately 24% of all passing leukocytes roll in cremaster venules of wild-type and P-selectin gene-deficient mice. Rolling in TNF-alpha-treated mice is unaffected by P-selectin mAb or E-selectin mAb 10E9.6. By contrast, rolling in TNF-alpha-treated P-selectin-deficient mice is completely blocked by L-selectin mAb. These data show that P-selectin is important during the initial induction of leukocyte rolling after tissue trauma. At later time points and in TNF-alpha-treated preparations, rolling is largely L-selectin dependent. Under the conditions tested, we are unable to find evidence for involvement of E-selectin in leukocyte rolling in mice.

Antibodies, Monoclonal↗

PubMed1995

Three populations of cells with dendritic morphology exist in peripheral blood, only one of which is infectable with human immunodeficiency virus type 1.

Conflicting data have been reported with regard to the infectability, dysfunction, and depletion of dendritic cells (DCs) in human immunodeficiency virus (HIV) disease. These discrepancies could potentially be explained by the existence of multiple subsets of cells with dendritic morphology in peripheral blood. The isolation of DCs in humans is accomplished through negative selection until a morphologically pure population is obtained. Recently, DC precursors purified from peripheral blood by negative selection have been observed to develop into functionally and morphologically mature DCs. In this report we identify three populations of cells in peripheral blood that have or can develop a dendritic morphology. The first population, when allowed to mature in culture, develops a dendritic morphology and gains the expression of HB15, a marker of DCs in blood, thymus, skin, and lymphoid organs. The second population expresses HB15 and has the phenotypic and morphologic characteristics of mature DCs. The third population is morphologically very similar to mature DCs but does not share the same T-cell-stimulatory activity and is the only population that is infectable with HIV. Understanding the heterogeneity of cells of dendritic lineage and/or morphology in the peripheral blood will aid in understanding their role as antigen-presenting cells in general and as potential participants in the immunopathogenesis of HIV disease.

Antigens, Surface↗

PubMed1995

Lectin and epidermal growth factor domains of P-selectin at physiologic density are the recognition unit for leukocyte binding.

P-selectin is an integral membrane glycoprotein on stimulated platelets and endothelial cells that serves as a receptor for leukocytes. To estimate the density of P-selectin in membranes necessary to support adhesion, we incorporated purified P-selectin at varying concentrations into phospholipid bilayers that encapsulated glass microspheres. Maximal binding of these lipospheres to HL60 cells, a P-selectin ligand-expressing cell line, was approached at a P-selectin density of about 100 molecules per microns 2; half-maximal binding was observed at about 50 to 60 molecules per microns 2. Compatible results were obtained with P-selectin expressed on Chinese hamster ovary cells. The P-selectin density on stimulated platelets was estimated to be 150 to 200 molecules/microns 2. To identify the domains of P-selectin required for HL60 cell binding, chimeras of P-selectin and L-selectin were stably expressed in Chinese hamster ovary cells and clones that expressed the chimeras at the estimated physiologic density were selected. Chimeras containing the P-selectin lectin and epidermal growth factor (EGF) domains or the lectin, EGF, and short consensus repeats bound HL60 cells equivalently, but a chimera containing the P-selectin lectin domain alone bound HL60 cells much less well. These results indicate that at a physiologically relevant P-selectin density on membrane surfaces, the lectin, and EGF domains of P-selectin are together required for optimal leukocyte binding.

Animals↗