Biomedical subjects

E C Butcher

Publications and source records attributed to E C Butcher.

At least 109 records · Page 6Linked to original sources

PubMed1995

Spatial distribution of L-selectin (CD62L) on human lymphocytes and transfected murine L1-2 cells.

We have examined the topographical distribution of L-selectin on surface membrane domains of human lymphocytes and murine L1-2 cells transfected to express human L-selectin. L-selectin was immunolocalized using murine monoclonal DREG 200 Fab antibody and a 12 nm colloidal gold-conjugated secondary antibody. Cell surface morphology and surface distribution of gold-labelled L-selectin were visualized using backscatter electron images obtained by high-resolution, field emission scanning electron microscopy. The topographical morphologies of lymphocytes of both types were complex. The surface of human lymphocytes was composed of both microvilli and ruffles; that of the murine cells was composed of long microvilli and few, if any, ruffles. L-selectin on human lymphocytes was observed primarily as focal clusters on the apical surfaces of ruffles and microvilli. Similarly, on the transfected murine cells, L-selectin was detected predominantly on the apical surface of microvilli. We conclude that L-selectin has a common spatial distribution and clustered organization on all leukocytes examined to-date, and that these features of receptor expression likely facilitate rolling of circulating leukocytes on the endothelial surface.

Animals↗

PubMed1995

Expression of the mucosal vascular addressin, MAdCAM-1, on sinus-lining cells in the spleen.

The MAdCAM-1 adhesion molecule is involved in lymphocyte homing into mucosal sites and is expressed on high endothelial venules of Peyer's patches and mesenteric lymph nodes. In the spleen, where high endothelial venules are absent, expression can be found on cells in the marginal zone between red and white pulp. By immunohistochemistry and electron microscopy it was demonstrated that in the spleen cells expressing MAdCAM-1 belong to the population of sinus-lining cells and that the expression is restricted to the sinus-lining cells closest to the lymphoid white pulp. Lymphocytes that migrate from the blood into this white pulp area will have to pass through the rim of cells expressing MAdCAM-1. A functional role for MAdCAM-1 or its lymphocyte ligand, the alpha 4 beta 7 integrin complex, was investigated by in vivo short-term homing experiments with anti-MAdCAM-1 and anti-alpha 4 beta 7 antibodies, but no direct role for this receptor-ligand interaction could be demonstrated.

Animals↗

PubMed1994

Sulfation-dependent recognition of high endothelial venules (HEV)-ligands by L-selectin and MECA 79, and adhesion-blocking monoclonal antibody.

L-selectin is a lectin-like receptor that mediates the attachment of lymphocytes to high endothelial venules (HEV) of lymph nodes during the process of lymphocyte recirculation. Two sulfated, mucin-like glycoproteins known as Sgp50/GlyCAM-1 and Sgp90/CD34 have previously been identified as HEV-associated ligands for L-selectin. These proteins were originally detected with an L-selectin/Ig chimera called LEC-IgG. GlyCAM-1 and CD34 are also recognized by an antiperipheral node addressin (PNAd) mAb called MECA 79, which blocks L-selectin-dependent adhesion and selectively stains lymph node HEV. The present study compares the requirements for the binding of MECA 79 and LEC-IgG to HEV-ligands. Whereas desialylation of GlyCAM-1 and CD34 drastically reduced binding to LEC-IgG, this treatment enhanced the binding of GlyCAM-1 to MECA 79. In contrast, the binding of both MECA 79 and LEC-IgG to GlyCAM-1 and CD34 was greatly decreased when the sulfation of these ligands was reduced with chlorate, a metabolic inhibitor of sulfation. Because MECA 79 stains HEV-like vessels at various sites of inflammation, recognition by L-selectin of ligands outside of secondary lymphoid organs may depend on sulfation. In addition to their reactivity with GlyCAM-1 and CD34, both MECA 79 and LEC-IgG recognize an independent molecule of approximately 200 kD in a sulfate-dependent manner. Thus, this molecule, which we designate Sgp200, is an additional ligand for L-selectin.

Amino Acid Sequence↗

PubMed1994

Neutrophils roll on adherent neutrophils bound to cytokine-induced endothelial cells via L-selectin on the rolling cells.

Specific arrest of neutrophils in venules is central to their rapid accumulation during local inflammatory responses. Initial neutrophil rolling on endothelium is mediated by leukocyte L-selectin and the inducible vascular adhesion proteins P- and E-selectin. This rolling is a prerequisite for endothelial-dependent neutrophil arrest. Here we describe rolling of neutrophils on the surface of previously arrested neutrophils and demonstrate that this interaction involves L-selectin exclusively on rolling cells. The adherent neutrophil support of L-selectin-dependent neutrophil rolling in vivo can promote continuous and augmented leukocyte recruitment at sites of previous neutrophil accumulation.

Antibodies, Monoclonal↗

PubMed1994

Distinct but overlapping epitopes are involved in alpha 4 beta 7-mediated adhesion to vascular cell adhesion molecule-1, mucosal addressin-1, fibronectin, and lymphocyte aggregation.

The mouse CD8+ T cell lymphoma TK1 expresses high levels of alpha 4 beta 7 integrin, which it can use to interact with multiple ligands including mucosal addressin-1 (MAdCAM-1), VCAM-1, and fibronectin. In addition, alpha 4 beta 7 can support TK1 cell aggregation. Here we have produced and characterized a panel of mAbs against alpha 4 beta 7 to define antigenic and functional epitopes associated with its distinct functions. One mAb, DATK32, is unique in recognizing an epitope specific to the alpha 4 beta 7 heterodimer. Furthermore, DATK32 induces TK1 cell aggregation yet inhibits TK1 cell adhesion to MAdCAM-1, VCAM-1, and fibronectin. Considered as a whole, the panel of anti-alpha 4 beta 7 mAbs studied define unique patterns of inhibition for alpha 4 beta 7 binding to each of its defined molecular ligands. We conclude that alpha 4 beta 7 interactions with MAdCAM-1, VCAM-1, and fibronectin can be modulated by Ab binding to distinct epitopes and thus probably involve functionally separable, although physically overlapping binding sites on this multifunctional integrin. These findings are consistent with the general observation that integrins use distinct, potentially differentially regulated interaction sites for adhesion to multiple ligands. Extension of these concepts to alpha 4 beta 7 has important considerations for understanding the roles of this integrin in lymphocyte homing to mucosal sites and in cell-cell interactions during the immune response.

Animals↗

PubMed1994

L-selectin and very late antigen-4 integrin promote eosinophil rolling at physiological shear rates in vivo.

Adherence of eosinophils to vascular endothelium and their accumulation at sites of allergen challenge are hallmarks of allergic inflammation. However, the molecular mechanisms mediating eosinophil adhesion under conditions of blood flow are not well understood. The present studies were performed to identify the receptors on human eosinophils involved in initiating adhesion to activated endothelium at physiologic shear rates in vivo. We have compared the relative contribution of L-selectin, VLA-4 (CD49d), and CD18 integrins in mediating eosinophil adhesion to microvascular endothelial cells in the rabbit mesentery by using intravital video microscopy. Eosinophils were found to roll in venules, but not arterioles, and this rolling could be stimulated by activation of endothelium with IL-1. In contrast to neutrophil rolling, which is predominantly L-selectin-dependent, eosinophil rolling was mediated by L-selectin, and also VLA-4. mAbs to L-selectin and VLA-4 alpha, but not CD18, significantly inhibited eosinophil rolling in vivo. The inhibition of VLA-4-mediated eosinophil rolling was not caused by modulation of eosinophil L-selectin or CD18 expression. This inhibition also was not caused by nonspecific inhibitory effect of the Abs studied, because the anti-VLA-4 mAbs inhibited eosinophil (VLA-4+) but not neutrophil (VLA-4-) rolling in the mesenteric venules. These results demonstrate that early events of eosinophil adhesion, i.e., rolling, are mediated by multiple adhesion receptors, including L-selectin and VLA-4, at physiologic shear rates in vivo.

Animals↗

PubMed1994

E-selectin mediates leukocyte rolling in interleukin-1-treated rabbit mesentery venules.

The selectins are lectin-like cell surface glycoproteins that have been implicated in playing a crucial role in the initiation of leukocyte adhesion to endothelial cells (ECs) during inflammation. Binding of selectins under conditions of flow mediates leukocyte rolling, which in vivo is almost exclusively observed in venular microvessels. We have shown in previous experiments that intraperitoneal treatment of rabbits with interleukin-1 beta (IL-1) increases leukocyte rolling in exteriorized mesenteries. In the present study, we used immunohistochemistry of mesenteries and found that IL-1 induced a marked E-selectin immunoreactivity, preferentially in venules. We therefore hypothesized that the increased rolling in response to IL-1 may be related to the induction of E-selectin on venular ECs. Intravital microscopy was used to investigate interactions between leukocytes and ECs after intraperitoneal application of IL-1. The rabbit E-selectin monoclonal antibody (MoAb) 9H9 significantly reduced rolling of leukocytes by approximately 40%. Vehicle alone, class-matched control MoAb or the nonblocking anti-E-selectin MoAb 14G2 had no effect on rolling. These results indicate that leukocytes roll on inflamed venular ECs partly through interactions with E-selectin. Furthermore, we propose that the restricted E-selectin immunoreactivity by venular ECs contributes to the remarkable difference seen between arterioles and venules in exhibiting leukocyte rolling in vivo.

Animals↗

PubMed1994

Expression and function of the MAdCAM-1 receptor, integrin alpha 4 beta 7, on human leukocytes.

Recirculation of mouse lymphocytes to the gut involves binding of the lymphocyte integrin alpha 4 beta 7 to the mucosal vascular addressin, MAdCAM-1. In humans, indirect evidence suggests that CD4+ T cells that express high levels of alpha 4 beta 7 migrate selectively to the gut. We now report that human adult blood CD8+ T cells and B cells, like CD4+ T cells, have heterogeneous expression of alpha 4 beta 7. In contrast, NK cells, eosinophils, and newborn blood T and B cells have relatively homogeneous expression of alpha 4 beta 7. CD4+ and CD8+ T cell expression of alpha 4 beta 7 was related to age, CD45RA expression, and integrin beta 1 (CD29) expression, suggesting that alpha 4 beta 7 expression changes after primary activation of CD4+ and CD8+ T cells in vivo. To directly determine whether human alpha 4 beta 7 mediates adhesion to MAdCAM-1, we performed in vitro adhesion assays with two alpha 4 beta 7+ human lymphoma cell lines. The results indicate that human alpha 4 beta 7 is a receptor for MAdCAM-1, whereas alpha 4 beta 1 is not. Adhesion of HUT 78 cells to MAdCAM-1 required Mn2+, whereas adhesion of RPMI 8866 cells did not, suggesting that alpha 4 beta 7 may have at least two distinct functional states. The ability of lymphocytes to bind to MAdCAM-1 and recirculate to mucosal organs is likely to be influenced both by the level of alpha 4 beta 7 expression and by the functional state of the alpha 4 beta 7 molecule.

Adult↗

PubMed1994

Ligand-induced adhesion to activated endothelium and to vascular cell adhesion molecule-1 in lymphocytes transfected with the N-formyl peptide receptor.

Binding of FMLP to the neutrophil N-formyl peptide receptor (FPR) transmits signals through pertussis toxin-sensitive G proteins triggering Ca2+ flux, superoxide production, granule exocytosis, and neutrophil aggregation and adhesion involving the beta 2 (CD18) integrins. Expression of the FPR in mouse fibroblasts or human kidney cells has been shown to confer an N-formyl peptide-inducible Ca2+ flux in transfectants. Here we demonstrate that the transfected receptor can also support ligand-induced alterations in cellular adhesion. We established stable transfectants of mouse L1-2 pre-B cells with cDNA for human FPR (L1-2 FPR cells). The transfectants bind N-formyl-Nle-Leu-Phe-Nle-Tyr-Lys-fluorescein with 1.4 x 10(5) sites per cell and a dissociation constant of 3.3 nM. Stimulation with FMLP induces a transient Ca2+ flux. FMLP also triggers adhesion of L1-2 FPR cells to TNF-alpha- or LPS-activated bEnd3 cells (mouse brain-derived endothelial cells) and to purified mouse VCAM-1. Binding is inhibited by Abs to VCAM-1 and to the alpha-chain of its lymphocyte receptor (the alpha 4 beta 1 integrin, VLA-4). Stimulation with FMLP does not induce a change in cell surface expression of alpha 4. Induced adhesion to VCAM-1 is rapid, detectable at the earliest times measurable (30 to 60 s after FMLP addition), and is inhibited by pertussis toxin. We conclude that FPR can mediate integrin activation not only in neutrophils but also in lymphocytes, and can trigger rapid adhesion via lymphocyte alpha 4 beta 1. The adhesion of lymphocytes is critical to their migration and targeting; our results suggest the possibility of manipulating adhesive responses through expression of chemoattractant receptors in lymphoid cells engineered for cellular therapy, allowing targeted adhesion and potentially migration in response to locally administered ligands.

Animals↗

PubMed1994

Role of alpha 4-integrins in lymphocyte homing to mucosal tissues in vivo.

Lymphocyte recirculation through different organs is thought to be regulated by adhesion molecules ("homing receptors") recognizing tissue-specific vascular addressins on endothelium. Here we show that the alpha 4/beta 7-integrin has a key role in the migration of mouse lymphocytes to mucosal sites. Homing to Peyer's patches but not to peripheral lymph nodes is inhibited by Fab fragments of mAb PS/2 against the alpha 4-integrin chain, by mAb DATK32 recognizing a combinatorial epitope on the alpha 4/beta 7-integrin, and by mAb FIB30 against the beta 7-chain. The Abs significantly reduce homing of lymphocytes to the intestine, as well. The migration of immunoblasts to gut and gut-associated lymphoid tissue also involves the alpha 4/beta 7-integrin heterodimer. Another anti-alpha 4 Ab, R1-2, which blocks lymphocyte binding to Peyer's patches in the Stamper-Woodruff frozen section assay and lymphocyte adhesion to VCAM-1 and fibronectin, has only minor effects on lymphocyte traffic in vivo. Anti-VCAM-1 Ab as well as the fibronectin peptide CS-1 are without influence on the migration to Peyer's patches or intestine, in contrast to Ab against the mucosal addressin MAdCAM-1. Thus, homing to gut-associated sites is regulated by the alpha 4/beta 7-integrin heterodimer interacting with the vascular addressin, MAdCAM-1, and not with fibronectin or VCAM-1 as counterstructures. Inhibition of homing to Peyer's patches and intestine by the anti-integrin Abs studied was only partial. L-selectin also participates in the homing of small lymphocytes to mucosal sites, especially Peyer's patches, but does not contribute substantially to the localization of blasts into the intestinal wall. The results support a major, but not exclusive role of the alpha 4/beta 7-integrin in lymphocyte traffic to mucosal sites.

Animals↗

PubMed1994

Cloning and expression of a cDNA encoding mouse endoglin, an endothelial cell TGF-beta ligand.

The rat monoclonal antibody, MJ7/18, which reacts selectively with the endothelium of blood vessels in mouse was used to screen a cDNA library derived from a transformed mouse brain endothelial cell line. The sequence of a cDNA encoding the cell surface MJ7/18 antigen revealed homology to human endoglin, a homodimeric transforming growth factor-beta (TGF-beta)-binding cell-surface glycoprotein expressed predominantly on vascular endothelial cells. Northern blot analysis shows a 3.4-kb single transcript of the mouse endoglin. The mouse endoglin is a type-I integral membrane protein of 653 amino acids (aa). The human and mouse sequences display 71% aa sequence identity with almost identical transmembrane and cytoplasmic domains. Like its human counterpart, mouse endoglin displays significant sequence homology to the type-III TGF-beta receptor in two extracellular domains, as well as striking similarity in the transmembrane and cytoplasmic regions. One of the extracellular regions of homology with TGF-beta receptor III represents a truncated version of a homology unit defining a novel gene family including uromodulin, the pancreatic granule protein gp2, and zona pellucida receptors for sperm. However, unlike its human counterpart, mouse endoglin does not contain an RGD tripeptide which has been suggested as a ligand of integrins.

Amino Acid Sequence↗

PubMed1994

Cell adhesion molecules on vessels during inflammation in the mouse central nervous system.

The expression of endothelial cell adhesion molecules (CAMs) in the central nervous system (CNS) of the mouse was examined during an inflammation induced by intracerebral injection of killed Corynebacterium parvum (C. parvum). We showed that injection of killed C. parvum produced an inflammatory cellular infiltrate limited to the injected brain hemisphere. However, the upregulation of ICAM-1 and VCAM-1 on brain endothelium occurred starting 2 days after C. parvum injection throughout the entire CNS and was not restricted to vessels surrounded by a cellular infiltrate. In contrast to the systemic upregulation of ICAM-1 and VCAM-1, cerebral vessels located in the center of the cellular infiltrate started to express the MECA-32 antigen, suggesting an altered functional status of the endothelial cells, as this antigen is suppressed during development of the blood-brain barrier (BBB). Binding assays performed on frozen sections of inflamed brains are consistent with an important role for endothelial VCAM-1 in the recruitment of lymphocytes during inflammation in the CNS of the mouse.

Animals↗

PubMed1994

Enhanced endothelial adhesiveness in hypercholesterolemia is attenuated by L-arginine.

BACKGROUND: We have shown that chronic administration of the nitric oxide (NO) precursor L-arginine normalizes NO-dependent vasodilation and markedly inhibits atherogenesis in a hypercholesterolemic rabbit model. We hypothesized that this antiatherogenic effect is due to modulation of endothelial adhesiveness by endothelium-derived NO. METHODS AND RESULTS: New Zealand White rabbits were fed normal chow (Cont), a high-cholesterol diet (Chol), a high-cholesterol diet supplemented with L-arginine (Arg), or a normal diet supplemented with the NO synthase antagonist L-nitroarginine (L-NA) for 2 weeks. In additional studies, some animals receiving L-NA were also treated with hydralazine to normalize blood pressure. After 2 weeks, thoracic aortas were harvested, opened longitudinally, and placed in a culture dish with the endothelial surface exposed to medium containing WEHI 78/24 cells, a monocytoid cell line. After incubation with the monocytoid cells for 30 minutes on a rocking platform, the aortic segments were washed repeatedly to remove nonadherent cells and adherent cells counted by epifluorescent microscopy. Monocytoid cell binding to aortic endothelium was significantly increased in Chol (P < .001 versus Cont); binding was markedly reduced in arginine-fed hypercholesterolemic animals (P < .05, Arg versus Chol). Monocytoid cell binding to aortic endothelium was also significantly increased in L-NA (P < .05); hydralazine normalized blood pressure but did not reduce monocytoid cell binding. To confirm that alterations in NO activity modulate endothelial cell-monocyte interaction, the release of nitrogen oxides (NOx) by thoracic aortas was assessed by a chemiluminescent technique. The concentration of NOx in the conditioned medium from segments of Arg thoracic aortas was significantly greater than that from Cont aortas, whereas that from L-NA aortas was significantly less. CONCLUSIONS: Hypercholesterolemia enhances the adhesiveness of aortic endothelium for monocytes; this effect is attenuated by dietary L-arginine. Conversely, inhibition of NO synthesis enhances monocyte binding. The results suggest that endothelium-derived NO plays an important role in regulating the endothelial adhesiveness for monocytes. Alterations in NO activity may play a critical role in atherogenesis.

Animals↗

PubMed1994

Evidence for involvement of ICAM-1 and VCAM-1 in lymphocyte interaction with endothelium in experimental autoimmune encephalomyelitis in the central nervous system in the SJL/J mouse.

We have investigated the expression of vascular adhesion molecules during the first stage of chronic inflammation in experimental autoimmune encephalomyelitis in the SJL/J mouse. Immunocytochemical analysis of frozen sections of inflamed versus noninflamed brains and spinal cords showed that the vascular endothelium in brains and spinal cords from diseased animals expressed high levels of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) but no detectable mucosal addressin or peripheral lymph node addressin. In frozen section assays, anti-alpha 4 integrin and anti-VCAM-1 monoclonal antibodies inhibited binding of mouse peripheral lymphocytes to inflamed brains at both 4 C and 20 C. Antilymphocyte function-associated antigen-1 and anti-ICAM-1 monoclonal antibodies inhibited binding of mouse peripheral lymphocytes to inflamed brains at 20 C. These results are consistent with an important role for the vascular adhesion molecules VCAM-1 and ICAM-1 and for their lymphocytes receptors in lymphocyte recruitment to the central nervous system.

Animals↗

PubMed1993

L-selectin-mediated lymphocyte rolling on MAdCAM-1.

The L-selectin, a cell surface C-type lectin, directs lymphocyte traffic to lymph nodes, and contributes to lymphocyte homing to Peyer's patches and to leukocyte interactions with inflamed venules. Here we report that the mucosal vascular addressin MAdCAM-1, a mucosal endothelial adhesion molecule with immunoglobulin- and mucin-like domains, is a facultative ligand for L-selectin. MAdCAM-1 isolated from mesenteric lymph nodes, but not from cultured endothelioma cells, bears N-glycanase-resistant sialic acid-containing carbohydrate which supports adhesion of L-selectin-transfected lymphoid cells under shear. Interacting lymphoid cells display a 'rolling' behaviour similar to the selectin-dependent rolling of neutrophils observed in inflamed venules. MAdCAM-1 is also a ligand for the lymphocyte integrin homing receptor for Peyer's patches, alpha 4 beta 7 (ref. 7), and may be uniquely adapted to support both selectin-mediated lymphocyte rolling and integrin-mediated adhesion and arrest in vivo.

Animals↗

PubMed1993

The Peyer's patch high endothelial receptor for lymphocytes, the mucosal vascular addressin, is induced on a murine endothelial cell line by tumor necrosis factor-alpha and IL-1.

The specificity of lymphocyte homing from the blood into a tissue is determined in part by complementary pairs of adhesion receptors on lymphocytes and endothelial cells termed homing receptors and vascular addressins, respectively. The mucosal vascular addressin involved in lymphocyte homing to Peyer's patches is a 66-kDa glycoprotein, MAdCAM-1. Investigation of the regulation and molecular genetics of MAdCAM-1 have been hampered by the lack of a murine cell line expressing this adhesion molecule. We show herein using indirect immunofluorescence studies that MAdCAM-1 can be induced on a murine endothelial cell line, bEnd.3, by cytokines and LPS. Western blot analysis of MAdCAM-1 purified by affinity column chromatography from TNF-alpha-treated bEnd.3 cells demonstrates a 66-kDa protein that comigrates in SDS-PAGE with the MAdCAM-1 constitutively found on high endothelial venules in murine mesenteric lymph nodes. Comparison of MAdCAM-1 expression on the bEnd.3 cells was made to the expression of adhesion molecules ICAM-1 and VCAM-1. MAdCAM-1 and VCAM-1 are not constitutively expressed on the bEND.3 surface but can be induced in a concentration-dependent manner by LPS, TNF-alpha, and IL-1. ICAM-1 is constitutively expressed on the endothelioma surface and expression is increased by TNF-alpha, IL-1, LPS, and IFN-gamma. Surface expression of MAdCAM-1 peaks 12 to 18 h after exposure to TNF-alpha and remains elevated at 48 h, whereas expression of VCAM-1 peaks at 4 h and inducible ICAM-1 peaks between 4 and 18 h. Interestingly, IFN-gamma has differential effects on expression of these three adhesion receptors. IFN-gamma alone induces VCAM-1 and enhances ICAM-1 expression, but does not induce MAdCAM-1. Furthermore, although, preincubation of bEND.3 cells with IFN-gamma modestly increases the induction of ICAM-1 and VCAM-1 in response to TNF-alpha and IL-1, it dramatically reduces the TNF-alpha, IL-1, and LPS-induced expression of MAdCAM-1. MAdCAM-1 on bEnd.3 cells is functional as the murine T lymphoma TK1, known to bind MAdCAM-1, also binds to TNF-alpha-stimulated endothelioma but not to unstimulated cells. This binding is blocked by the antibodies against MAdCAM-1 and against the alpha 4-chain of its integrin receptor, alpha 4 beta 7, on TK1 cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1993

Alpha 4 beta 7 integrin mediates lymphocyte binding to the mucosal vascular addressin MAdCAM-1.

The mucosal vascular addressin, MAdCAM-1, is an immunoglobulin superfamily adhesion molecule for lymphocytes that is expressed by mucosal venules and helps direct lymphocyte traffic into Peyer's patches (PP) and the intestinal lamina propria. We demonstrate that the lymphocyte integrin alpha 4 beta 7, also implicated in homing to PP, is a receptor for MAdCAM-1. Certain antibodies to alpha 4 and beta 7 integrin chains but not to the beta 2 integrin LFA-1 inhibit lymphocyte binding to purified MAdCAM-1 and to MAdCAM-1 transfectants. Lymph node lymphocytes, alpha 4 beta 7+ TK1 lymphoma cells, and a beta 7-transfected variant of an alpha 4+ B cell line, 38C13, bind constitutively to MAdCAM-1. Binding is enhanced by Mn(++)-induced integrin activation. The related integrin alpha 4 beta 1 supports efficient binding to VCAM-1 but not to MAdCAM-1, even after integrin activation, indicating that MAdCAM-1 is a preferential ligand for alpha 4 beta 7. Alpha 4 beta 7 can also bind VCAM-1, but this requires greater integrin activation than binding to MAdCAM-1. The findings imply a selective role for the interaction of alpha 4 beta 7 and MAdCAM-1 lymphocyte in homing to mucosal sites.

Animals↗

PubMed1993

Rapid G protein-regulated activation event involved in lymphocyte binding to high endothelial venules.

The homing of blood borne lymphocytes into lymph nodes and Peyer's patches is mediated in part by recognition and binding to specialized high endothelial venules (HEV). Here we demonstrate that a rapid pertussis toxin-sensitive lymphocyte activation event can participate in lymphocyte recognition of HEV. In situ video microscopic analyses of lymphocyte interactions with HEV in exteriorized mouse Peyer's patches reveal that pertussis toxin has no effect on an initial "rolling" displayed by many lymphocytes, but inhibits an activation-dependent "sticking" event required for lymphocyte arrest. This is the first demonstration that physiologic lymphocyte-endothelial interactions can involve sequential rolling, activation, and activation-dependent arrest, previously shown only for neutrophils. The inhibitory effect of the toxin is dependent on its G protein-modifying ADP-ribosyltransferase activity and can be reversed by phorbol myristic acetate, which bypasses cell surface receptors to trigger activation-dependent adhesion. Lymphocyte sticking can occur within 1-3 s after initiation of rolling. We conclude that a rapid receptor-mediated activation event involving G protein signaling can trigger stable lymphocyte attachment to HEV in vivo, and may play a critical role in regulating lymphocyte homing.

Animals↗