Biomedical subjects

Jens V Stein

Publications and source records attributed to Jens V Stein.

9 recordsLinked to original sources

PubMed2006

DOCK2 is required for chemokine-promoted human T lymphocyte adhesion under shear stress mediated by the integrin alpha4beta1.

The alpha4beta1 integrin is an essential adhesion molecule for recruitment of circulating lymphocytes into lymphoid organs and peripheral sites of inflammation. Chemokines stimulate alpha4beta1 adhesive activity allowing lymphocyte arrest on endothelium and subsequent diapedesis. Activation of the GTPase Rac by the guanine-nucleotide exchange factor Vav1 promoted by CXCL12 controls T lymphocyte adhesion mediated by alpha4beta1. In this study, we investigated the role of DOCK2, a lymphocyte guanine-nucleotide exchange factor also involved in Rac activation, in CXCL12-stimulated human T lymphocyte adhesion mediated by alpha4beta1. Using T cells transfected with DOCK2 mutant forms defective in Rac activation or with DOCK2 small interfering RNA, we demonstrate that DOCK2 is needed for efficient chemokine-stimulated lymphocyte attachment to VCAM-1 under shear stress. Flow chamber, soluble binding, and cell spreading assays identified the strengthening of alpha4beta1-VCAM-1 interaction, involving high affinity alpha4beta1 conformations, as the adhesion step mainly controlled by DOCK2 activity. The comparison of DOCK2 and Vav1 involvement in CXCL12-promoted Rac activation and alpha4beta1-dependent human T cell adhesion indicated a more prominent role of Vav1 than DOCK2. These results suggest that DOCK2-mediated signaling regulates chemokine-stimulated human T lymphocyte alpha4beta1 adhesive activity, and that cooperation with Vav1 might be required to induce sufficient Rac activation for efficient adhesion. In contrast, flow chamber experiments using lymph node and spleen T cells from DOCK2(-/-) mice revealed no significant alterations in CXCL12-promoted adhesion mediated by alpha4beta1, indicating that DOCK2 activity is dispensable for triggering of this adhesion in mouse T cells, and suggesting that Rac activation plays minor roles in this process.

Animals↗

PubMed2006

Opioids trigger alpha 5 beta 1 integrin-mediated monocyte adhesion.

Inflammatory reactions involve a network of chemical and molecular signals that initiate and maintain host response. In inflamed tissue, immune system cells generate opioid peptides that contribute to potent analgesia by acting on specific peripheral sensory neurons. In this study, we show that opioids also modulate immune cell function in vitro and in vivo. By binding to its specific receptor, the opioid receptor-specific ligand DPDPE triggers monocyte adhesion. Integrins have a key role in this process, as adhesion is abrogated in cells treated with specific neutralizing anti-alpha5beta1 integrin mAb. We found that DPDPE-triggered monocyte adhesion requires PI3Kgamma activation and involves Src kinases, the guanine nucleotide exchange factor Vav-1, and the small GTPase Rac1. DPDPE also induces adhesion of pertussis toxin-treated cells, indicating involvement of G proteins other than Gi. These data show that opioids have important implications in regulating leukocyte trafficking, adding a new function to their known effects as immune response modulators.

Animals↗

PubMed2005

Vav1 and Rac control chemokine-promoted T lymphocyte adhesion mediated by the integrin alpha4beta1.

The chemokine CXCL12 promotes T lymphocyte adhesion mediated by the integrin alpha4beta1. CXCL12 activates the GTPase Rac, as well as Vav1, a guanine-nucleotide exchange factor for Rac, concomitant with up-regulation of alpha4beta1-dependent adhesion. Inhibition of CXCL12-promoted Rac and Vav1 activation by transfection of dominant negative Rac or Vav1 forms, or by transfection of their siRNA, remarkably impaired the increase in T lymphocyte attachment to alpha4beta1 ligands in response to this chemokine. Importantly, inhibition of Vav1 expression by RNA interference resulted in a blockade of Rac activation in response to CXCL12. Adhesions in flow chambers and soluble binding assays using these transfectants indicated that initial ligand binding and adhesion strengthening mediated by alpha4beta1 were dependent on Vav1 and Rac activation by CXCL12. Finally, CXCL12-promoted T-cell transendothelial migration involving alpha4beta1-mediated adhesion was notably inhibited by expression of dominant negative Vav1 and Rac. These results indicate that activation of Vav1-Rac signaling pathway by CXCL12 represents an important inside-out event controlling efficient up-regulation of alpha4beta1-dependent T lymphocyte adhesion.

Blotting, Western↗

PubMed2005

Chemokine control of lymphocyte trafficking: a general overview.

Chemokines are a large family of small, generally secreted polypeptides which guide lymphocyte movement throughout the body by controlling integrin avidity and inducing migration. Here, we look at recent, exciting findings on chemokine function throughout lymphocyte development and co-ordinated T and B cell migration during immune responses. Finally, we will review data on the regional control of immunity by tissue-specific chemokine receptors on effector/memory lymphocytes.

Animals↗

PubMed2004

CXCL12 mediates CCR7-independent homing of central memory cells, but not naive T cells, in peripheral lymph nodes.

Central memory CD8(+) T cells (T(CM)) confer superior protective immunity against infections compared with other T cell subsets. T(CM) recirculate mainly through secondary lymphoid organs, including peripheral lymph nodes (PLNs). Here, we report that T(CM), unlike naive T cells, can home to PLNs in both a CCR7-dependent and -independent manner. Homing experiments in paucity of lymph node T cells (plt/plt) mice, which do not express CCR7 ligands in secondary lymphoid organs, revealed that T(CM) migrate to PLNs at approximately 20% of wild-type (WT) levels, whereas homing of naive T cells was reduced by 95%. Accordingly, a large fraction of endogenous CD8(+) T cells in plt/plt PLNs displayed a T(CM) phenotype. Intravital microscopy of plt/plt subiliac lymph nodes showed that T(CM) rolled and firmly adhered (sticking) in high endothelial venules (HEVs), whereas naive T cells were incapable of sticking. Sticking of T(CM) in plt/plt HEVs was pertussis toxin sensitive and was blocked by anti-CXCL12 (SDF-1alpha). Anti-CXCL12 also reduced homing of T(CM) to PLNs in WT animals by 20%, indicating a nonredundant role for this chemokine in the presence of physiologic CCR7 agonists. Together, these data distinguish naive T cells from T(CM), whereby only the latter display greater migratory flexibility by virtue of their increased responsiveness to both CCR7 ligands and CXCL12 during homing to PLN.

Animals↗

PubMed2004

Differential requirements for DOCK2 and phosphoinositide-3-kinase gamma during T and B lymphocyte homing.

Chemokines guide lymphocytes from blood to secondary lymphoid organs by triggering integrin-dependent firm adhesion under vascular flow and directed migration of T and B lymphocytes within lymphoid tissue. Here, we analyze the roles of DOCK2, a mammalian homolog of Caenorhabditis elegans CED-5 and Drosophila melanogaster Myoblast City, and phosphoinositide-3-kinase (PI3K) during lymphocyte recirculation. DOCK2 mediated efficient lymphocyte migration in a largely PI3K-independent manner, although a minor, PI3K-dependent pathway for migration was observed in wild-type and DOCK2-deficient lymphocytes. In T cells, this residual migration depended mainly on PI3Kgamma, whereas other PI3K isoforms were implicated in B cells. In vitro adhesion assays and intravital microscopy of lymphoid organ vasculature uncovered an unexpected defect in integrin activation in DOCK2-/- B cells, whereas lack of DOCK2 did not affect chemokine-triggered integrin activation in T cells. DOCK2 and PI3Kgamma thus play distinct roles during T and B cell integrin activation and migration.

Actins↗

PubMed2003

DOCK2 regulates Rac activation and cytoskeletal reorganization through interaction with ELMO1.

Although the migratory property of lymphocytes is critical for protective immunity, tissue infiltration of lymphocytes sometimes causes harmful immune responses. DOCK2 plays a critical role in lymphocyte migration by regulating actin cytoskeleton through Rac activation, yet the mechanism by which DOCK2 activates Rac remains unknown. We found that DOCK2 associates with engulfment and cell motility (ELMO1) through its Src-homology 3 (SH3) domain. When DOCK2 was expressed in T-hybridoma cells lacking endogenous expression of DOCK2, Rac activation and actin polymerization were induced. However, such responses were not elicited by the DOCK2 mutant lacking the region required for ELMO1 binding. On the other hand, we found that the expression of ELMO1 induces Rac activation in the plasmacytoma cells expressing DOCK2 but not ELMO1. These results indicate that the association of DOCK2 with ELMO1 is critical for DOCK2-mediated Rac activation, thereby suggesting that their association might be a therapeutic target for immunologic disorders caused by lymphocyte infiltration.

Actins↗

PubMed2002

CCR7-mediated physiological lymphocyte homing involves activation of a tyrosine kinase pathway.

Homing of blood-borne lymphocytes to peripheral lymph nodes (PLNs) is a multistep process dependent on the sequential engagement of L-selectin, which mediates lymphocyte rolling along the luminal surface of high endothelial venules (HEVs), followed by activation of lymphocyte integrins and transmigration through HEVs. Within lymphoid tissue, B and T lymphocytes then migrate toward specific microenvironments such as B-cell follicles and the paracortex, respectively. The lymphocyte-expressed chemokine receptor CCR7 is playing an important role during this process, as its HEV-presented ligands CCL19 and CCL21 can trigger rapid integrin activation under flow in addition to inducing a chemotactic response, which may participate in transmigration and/or interstitial migration. Here, we report that Tyrphostin (Tyr) AG490, a pharmacological inhibitor of Janus family tyrosine kinases (Jaks), blocked the chemotactic response of primary mouse lymphocytes to CCL19 and CCL21 in a dose-dependent manner. Furthermore, Tyr AG490 inhibited rapid CCL21-mediated up-regulation of alpha4 and beta2 integrin adhesiveness in static adhesion assays and under physiological flow, whereas adhesion induced by phorbol myristate acetate remained unaltered. Using intravital microscopy of subiliac PLNs in mice, we found that adoptively transferred Tyr AG490-treated lymphocytes adhered significantly less in HEVs compared with control cells, although L-selectin-mediated rolling was similar in both samples. Finally, we observed rapid Jak2 phosphorylation in CCL21-stimulated primary mouse lymphocytes. Thus, our study suggests a role for Jak tyrosine kinases during CCR7-mediated lymphocyte recirculation.

Animals↗

PubMed2002

APRIL modulates B and T cell immunity.

The TNF-like ligands APRIL and BLyS are close relatives and share the capacity to bind the receptors TACI and BCMA. BLyS has been shown to play an important role in B cell homeostasis and autoimmunity, but the biological role of APRIL remains less well defined. Analysis of T cells revealed an activation-dependent increase in APRIL mRNA expression. We therefore generated mice expressing APRIL as a transgene in T cells. These mice appeared normal and showed no signs of B cell hyperplasia. Transgenic T cells revealed a greatly enhanced survival in vitro as well as enhanced survival of staphylococcal enterotoxin B-reactive CD4+ T cells in vivo, which both directly correlate with elevated Bcl-2 levels. Analysis of humoral responses to T cell-dependent antigens in the transgenic mice indicated that APRIL affects only IgM but not IgG responses. In contrast, T cell-independent type 2 (TI-2) humoral response was enhanced in APRIL transgenic mice. As TACI was previously reported to be indispensable for TI-2 antibody formation, these results suggest a role for APRIL/TACI interactions in the generation of this response. Taken together, our data indicate that APRIL is involved in the induction and/or maintenance of T and B cell responses.

Animals↗