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Biomedical subjects

B Holzmann

Publications and source records attributed to B Holzmann.

At least 55 records · Page 3Linked to original sources
PubMed1996

Crucial role of 55-kilodalton TNF receptor in TNF-induced adhesion molecule expression and leukocyte organ infiltration.

Stimulation of leukocyte adhesion to the endothelium by TNF is mediated by the up-regulation of adhesion molecules on the endothelial cell surface. C57BL/6 mice and syngenic 55-kDa TNF receptor-deficient mice (TNFRp55-/- mice) were challenged with TNF, and the kinetics of intracellular adhesion molecule-1, ICAM-1, mucosal addressin cell adhesion molecule-1, vascular adhesion molecule-1 (VCAM-1), and E-selectin expression were examined in various organs. TNF induced sustained VCAM-1 expression within 4 h in lung, liver, and kidney. In the lungs, but not in other organs, transient E-selectin expression was induced by TNF within 0.5 h and peaked at 4 h. The TNF-induced expression of VCAM-1 and E-selectin was found to be exclusively controlled by the 55-kDa TNF-receptor (TNFRp55) as demonstrated by analysis of TNFRp55-/- mice. Furthermore, TNF triggered mononuclear cell and neutrophil infiltration of lung, liver, and kidney in C57BL/6 mice but not TNFRp55-/- mice. Interestingly, MAdCAM-1 expression in the marginal sinus of the spleen was detected in wild-type mice but was absent in TNFRp55-/- mice. Together, the data suggest that in vivo the 55-kDa TNF receptor mediates the induction of VCAM-1 and E-selectin expression and is critically involved in the control of leukocyte organ infiltration.

Animals↗
PubMed1995

Lymph node (but not spleen) invasion by murine lymphoma is both CD44- and hyaluronate-dependent.

Similar to activated T cells, LB T cell lymphoma expresses the CD44 cell surface Ag. In addition, the vast majority of LB cells also express the beta 2 (CD18) and alpha L (CD11a) chains of LFA-1 integrin. In view of the finding that anti-CD18 mAb blocked spleen, but not lymph node invasion by LB cells inoculated s.c. into BALB/c mice, we tested the ability of anti-CD44 mAb (IM 7.8.1) to block the infiltration of LB cells into the lymph nodes. We found that, as opposed to anti-CD18 mAb, anti-CD44 mAb, as well as its F(ab')2 or Fab fragment, prevented lymph node infiltration but had no effect on spleen invasion. This conclusion was based on histologic examination and [3H]thymidine incorporation into proliferating LB cells invading the lymphoid organs. Histologic analysis further demonstrated that LB cells invade the lymph node via the afferent lymphatics. The surface expression of CD44 molecules on LB cells was enhanced after PMA activation. PMA activation also enabled in vitro binding of the lymphoma to hyaluronic acid (HA), a known ligand of CD44. Because anti-CD44 mAb, its F(ab')2 or Fab fragment, and hyaluronidase blocked this binding, we also tested the ability of the enzyme to inhibit lymph node invasion by LB cells. We established through histologic examination and [3H]thymidine incorporation that hyaluronidase protected the lymph node, but not the spleen, from invasion by the lymphoma.

Animals↗
PubMed1995

Differential regulation of alpha 4 integrin-dependent binding to domains 1 and 4 of vascular cell adhesion molecule-1.

The vascular cell adhesion molecule-1 (VCAM-1) plays an important role in diverse physiological and pathological processes. The homologous first and fourth immunoglobulin-like domains of the seven domain form of VCAM-1 present binding motifs for alpha 4 beta 1 integrin. Using a panel of VCAM-1 domain deletion mutants we show that alpha 4 beta 7 integrin interacts with both domains 1 and 4. In contrast to their identical domain usage, alpha 4 beta 1 and alpha 4 beta 7 integrins differ in the activation states required for binding to domains 1 and 4 of VCAM-1. We show that integrin alpha 4 beta 1 required significantly higher concentrations of Mn2+ than integrin alpha 4 beta 7 to support half-maximal adhesion to domain 4. Moreover, a clear difference in the capacity of integrins alpha 4 beta 1 and alpha 4 beta 7 to interact with domain 4 was detected in the presence of Ca2+ and Mg2+ cations. Adhesion to domain 1 of VCAM-1, however, was not affected by integrin heterodimer composition. Instead, the activity level of integrin alpha 4 beta 1 for domain 1 binding was regulated by CD24 expression. Binding to seven domain VCAM-1 was not altered significantly by beta 1 and beta 7 subunits or CD24. These data indicate that integrin heterodimer composition and CD24 expression differentially modulate integrin binding to domains 1 and 4 of VCAM-1. Mechanisms that alter integrin binding specificity or monovalent versus divalent interactions may affect the strength of adhesion as well as signal transmission in adherent cells and may therefore be critical to controlling the cellular response to integrin occupancy.

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↗
PubMed1995

[Immunosuppression and infection].

The course of prolonged sepsis is characterized by an initial activation of the immune system followed by the transition into a state of immunosuppression. Accordingly, a series of immunosuppressive substances can be detected in the serum of septic patients. On the cellular level many important functions of the unspecific as well as the specific defense systems of the organism are inhibited. As a consequence, immunosuppression may be contributing to the fact, that patients suffering from prolonged sepsis hardly recover with a high risk to end in multiple organ dysfunction. However, increasing efforts to investigate this problem may result in therapeutic approaches which may help to improve the bad prognosis of sepsis.

Humans↗
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

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

Distinct binding specificities of integrins alpha 4 beta 7 (LPAM-1), alpha 4 beta 1 (VLA-4), and alpha IEL beta 7.

Integrin receptors are important for regulating lymphocyte recirculation and recruitment to sites of inflammation. Transfectants of the B cell lymphoma 38C13 were generated that differ exclusively in the expression of integrin beta 1 or beta 7 subunits allowing for a functional comparison of lymphocyte Peyer's patch HEV adhesion molecule 1 (LPAM-1) (alpha 4 beta 7) and very late antigen 4 (VLA-4) (alpha 4 beta 1) in an identical cellular environment. Whereas 38-beta 7 transfectants bound to purified and cellular mucosal addressin cell adhesion molecule (MAdCAM-1), unstimulated 38-beta 1 cells failed to bind MAdCAM-1. Treatment of 38-beta 1 cells with Mn2+ but not with PMA induced low level binding to MAdCAM-1. MAdCAM-1 adhesion of 38-beta 7 cells was constitutive and not enhanced by Mn2+ treatment. Similarly, MAdCAM-1-dependent adhesion to mucosal high endothelial venules was shown for 38-beta 7 but not for 38-beta 1 cells. The results therefore establish the LPAM-1-MAdCAM-1 interaction as the functionally dominant adhesion pathway for regulating lymphocyte homing to mucosal sites. Nonetheless, the activated VLA-4 on some lymphocytes may be involved in MAdCAM-1 recognition or promote binding to MAdCAM-1 in other tissues. By contrast, 38-beta 7 and 38-beta 1 transfectants did not differ in their binding capacity for vascular cell adhesion molecule 1 (VCAM-1) or fibronectin and LPAM-1 did not display any preference for interacting with either MAdCAM-1 or VCAM-1. LPAM-1 may therefore contribute significantly to cellular functions previously attributed to VLA-4. Interestingly, functional analysis of the intraepithelial lymphocyte integrin alpha IEL beta 7 which is structurally related to LPAM-1 did not reveal detectable binding activity for MAdCAM-1, VCAM-1, or fibronectin.

Animals↗
PubMed1993

Bacterial superantigens induce rapid and T cell receptor V beta-selective down-regulation of L-selectin (gp90Mel-14) in vivo.

Upon challenge of mice with bacterial superantigens such as staphylococcal enterotoxin B, several facets of TCR V beta-selective acute T-cell alterations can be observed, which include acute T cell priming, and systemic lymphokine release followed by ligand-specific unresponsiveness. Prompted by experiments showing that stimulation of T cells by phorbol esters in vitro results in rapid shedding of the L-selectin homing receptor, we investigated the expression of adhesion molecules on superantigen-responsive T cells in vivo. Here we show that bacterial superantigens cause TCR V beta-specific loss of L-selectin. Down-regulation of L-selectin was selective, since the expression of other lymphocyte surface receptors was not changed. L-Selectin down-regulation represents a superantigen-induced immediate cell surface alteration and was not observed on T cells stimulated by TCR-specific antibodies. Loss of expression was almost complete within 30 min, and recovered 50 h after challenge. The results suggest that acute loss of L-selectin is a hallmark of T cell activation by bacterial superantigens that may result in profound changes of T lymphocyte recirculation pathways.

Animals↗
PubMed1993

[Pneumonia due to a rare atypical Mycobacterium in AIDS].

A 38-year-old man, HIV-positive for 6 years, developed fever and cough with deterioration in his general state. Chest radiography demonstrated an infiltration in the left upper lobe and computed tomography showed a septated cavity. Three bronchioalveolar lavages over 4 weeks recovered Klebsiella, Candida, Pseudomonas and Staphylococcus in the lavage fluid. Acid-fast rods were not found in any of the microscopic preparations. His clinical condition and the radiological findings deteriorated despite appropriate antibiotic administration. A further cavity occurred in the right upper lobe and the inflammatory infiltrations extended further. Although no acid-fast organism had been demonstrated, tuberculostatic treatment was begun (daily 300 mg isoniazid, 600 mg rifampicin, 900 mg streptomycin, 2 g pyrazinamide). His general condition and the radiological findings rapidly improved. Four weeks after culturing the lavage fluid atypical Mycobacterium xenopi was isolated. This case illustrates the difficulty of diagnosing an atypical mycobacterial infection. It takes time and effort, but it is of great importance because up to 50% of patients with AIDS contract such infection. Early and appropriate treatment will significantly improve quality of life and life expectancy.

AIDS-Related Opportunistic Infections↗
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

Triggering of L-selectin (gp90MEL-14) induces homotypic lymphocyte adhesion by a mechanism independent of LFA-1.

The L-selectin adhesion receptor plays a central role in regulating leukocyte adhesion to endothelial cells. The data presented in this report demonstrate that triggering of L-selectin results in a rapid and vigorous homotypic adhesion among normal lymphocytes as well as lymphoblastoid cells, thereby providing evidence for a novel cell-cell adhesion function of L-selectin. The cellular adhesion event induced by mAb MEL-14 was dependent on metabolic energy, an intact cytoskeleton, and the activation of intracellular protein kinases. Cell clustering did not require cross-linking of L-selectin molecules and occurred in the complete absence of divalent cations. Analysis of adhesion receptor expression and antibody inhibition experiments indicated that cluster formation did not involve LFA-1, alpha 4 integrins, beta 1 integrins, beta 7 integrins, or CD44.

Animals↗
PubMed1992

Cloning and expression of mouse integrin beta p(beta 7): a functional role in Peyer's patch-specific lymphocyte homing.

Lymphocytes express integrin receptors, termed lymphocyte Peyer's patch high endothelial venule (HEV) adhesion molecules (LPAMs), that mediate their organ-specific adhesion to specialized HEVs found in mucosal lymphoid organs (Peyer's patches). LPAM-1 consists of a murine integrin alpha 4 noncovalently associated with integrin beta p. Here, we describe the cloning and expression of a mouse cDNA encoding beta p, which is an 806-amino acid transmembrane glycoprotein. The genomic Southern blot analysis indicates that beta p is the murine homologue of human beta 7. The function of alpha 4 beta 7 as a Peyer's patch-specific adhesion molecule was tested directly by expression of the murine beta 7 cDNA in an alpha 4+ beta 7-B-cell line or coexpression of the alpha 4 and beta 7 cDNAs in an alpha 4-beta 7-T-cell line. The transfected cells exhibited a new Peyer's patch-specific adhesive phenotype that could be specifically blocked by monoclonal antibodies against alpha 4 and beta 7. Moreover, an anti-beta 7 monoclonal antibody specifically blocked binding of normal lymphocytes to Peyer's patch HEV but did not inhibit their binding to peripheral lymph node HEVs, indicating that beta 7 is a unique component of the Peyer's patch-specific homing receptor.

Amino Acid Sequence↗
PubMed1992

Lymphocyte activation and regulation of three adhesion molecules with supposed function in homing: LECAM-1 (MEL-14 antigen), LPAM-1/2 (alpha 4-integrin) and CD44 (Pgp-1).

Directed migration of lymphocytes from blood into lymph nodes and gut-associated lymphatic tissue, also referred to as homing, is subject to change following activation. Lymphocyte migration into lymphoid organs in vivo and binding to high endothelial venules in vitro is largely suppressed after short-term stimulation with phorbol esters. The observed functional alterations were correlated with changes in the expression of three putative homing receptors, LECAM-1 (MEL-14 antigen), LPAM-1/2 (alpha 4-integrin) and the murine CD44 (Pgp-1, H-CAM, Hermes-antigen equivalent) upon different modes of cellular activation. Expression of LECAM-1 (gp90 MEL-14), a lymphocyte adhesion molecule implicated in targeting extravasation into lymph nodes, was found to be lost almost completely within minutes after protein kinase C activation. LECAM-1 re-expression occurred within less than 24 h. Rapid loss of LECAM-1 was also observed after calcium ionophores whereas anti-CD3 or concanavalin A elicited a gradual and heterogeneous loss of LECAM-1 becoming detectable after several hours only. A number of cytokines tested were not able to induce alterations in LECAM-1 expression. In contrast, expression of LPAM-1/2 (alpha 4-integrin) and CD44 (Pgp-1, H-CAM), two adhesion molecules supposed to direct extravasation into Peyer's patches, remained stable for hours after every stimulus tested; CD44 expression gradually increased 24 h after mitogenic activation, whereas a small reduction only was observed for the expression of the alpha 4-chain under certain conditions. Thus, reduced extravasation of lymphocytes into Peyer's patches after activation is not due to a decline in the surface density of LPAM-1/2 alpha-chain or CD44 whereas alterations in migration into lymph nodes parallel the expression of LECAM-1.

Animals↗
PubMed1992

Anti-oncogenic activity of signalling-defective epidermal growth factor receptor mutants.

Overexpression and autocrine activation of the epidermal growth factor receptor (EGF-R) cause transformation of cultured cells and correlate with tumor progression in cancer patients. Dimerization and transphosphorylation are crucial events in the process by which receptors with tyrosine kinase activity generate normal and transforming cellular signals. Interruption of this process by inactive receptor mutants offers the potential to inhibit ligand-induced cellular responses. Using recombinant retroviruses, we have examined the effects of signalling-incompetent EGF-R mutants on the growth-promoting and transforming potential of ligand-activated, overexpressed wild-type EGF-R and the v-erbB oncogene product. Expression of a soluble extracellular EGF-R domain had little if any effect on the growth and transformation of NIH 3T3 cells by either tyrosine kinase. However, both a kinase-negative EGF-R point mutant (HERK721A) and an EGF-R lacking 533 C-terminal amino acids efficiently inhibited wild-type EGF-R-mediated, de novo DNA synthesis and cell transformation in a dose-dependent manner. Furthermore, coexpression with the v-erbBES4 oncogene product in NIH 3T3 cells resulted in transphosphorylation of the HERK721A mutant receptor and reduced soft-agar colony growth but had no effect in a focus formation assay. These results demonstrate that signalling-defective receptor tyrosine kinase mutants differentially interfere with oncogenic signals generated by either overexpressed EGF-R or the retroviral v-erbBES4 oncogene product.

3T3 Cells↗