| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
* Leukocyte Adhesion Laboratory and
Fluorescence Activated Cell Sorter Laboratory, Cancer Research U.K. London Research Institute, London, United Kingdom
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
5
1 also leads to an
accumulation of cytoskeletal proteins and 20 signal transduction
molecules (1, 3). The interaction of integrins with the
cytoskeleton is dynamic, depending on both integrin signaling and the
state of the cytoskeletal organization within the cell (reviewed in
Ref. 4). Much less is known about the association in leukocytes of integrins with the cytoskeleton (5). Leukocytes are key migratory cells that relay information to other cells, and their correct functioning depends on successful cell:cell and cell:matrix contacts. For example, the leukocyte integrin, LFA-1, participates in the guided movement of leukocytes from the bloodstream across the vasculature toward the site of injury. LFA-1 also has a key role in the initiation of an immune response by providing adhesion strengthening at the immunological synapse where T cells make contact with APCs (6). The integrins on leukocytes, unlike those on fibroblasts, are constitutively inactive but receive activating stimuli through signaling from other cell surface receptors. Such receptor-mediated signaling not only will cause clustering of integrins like LFA-1 (7) but will also activate other intracellular signaling pathways. This has made it difficult to distinguish such signals, some of which are necessary for integrin activation, from those that might emanate from the integrin itself upon ligand binding.
In this study we have directly activated LFA-1 by manipulating the extracellular cation environment and have therefore bypassed the usual requirement for an intracellular integrin-activating event. This has allowed the signaling events initiated by integrin ligand binding to be analyzed in isolation from other intracellular signaling pathways (8, 9). The key finding is that the clustering of conformationally altered LFA-1 can independently signal the formation of an F-actin filament network, which is essential for T cell adhesion.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
mAb 38 (LFA-1 subunit, function blocking) was prepared in
this laboratory. Other Abs were mAb G25.2 (LFA-1 subunit,
non-function blocking; BD Biosciences, Oxford, U.K.), mAb UCHT1 (CD3;
(donated by Dr. P. Beverley, Jenner Vaccine Institute, Compton, U.K.),
and rabbit anti-mouse-IgG (DAKO, Cambridge, U.K.). The human
dimeric five-domain ICAM-1Fc chimeric protein was produced by
previously described methods (9). Labels
2',7'-bis-(carboxyethyl)-5(6')-carboxyfluorescein (Calbiochem,
Nottingham, U.K.), Alexa Fluor 488-, and TRITC-phalloidin were from
Cambridge Biosciences (Cambridge, U.K.). Cytoskeletal inhibitors used
were cytochalasin D (Sigma-Aldrich, Cambridge, Dorset, U.K.),
latrunculin A (from Dr. R Treisman, Cancer Research U.K., London,
U.K.), and jasplakinolide (Cambridge Biosciences). Primary 10- to
14-day-cultured T lymphoblasts were prepared as previously described
(9).
Flow cytometry and assessment of soluble dICAM-1 binding
T cells were washed in assay buffer (20 mM HEPES, 140 mM NaCl, 2 mg/ml glucose (pH 7.4)) and 2 x 105 T cells in 50 µl assay buffer/0.1% BSA/1–5 mM Mg2+/1 mM EGTA were added to flexiwell plate wells (Dynex Technologies, Ashford, U.K.) containing 50 µl of 2 µM dimeric ICAM (dICAM)-1Fc (saturated binding), with or without LFA-1 function-blocking mAb 38 (10 µg/ml) or cytochalasin D at a 0.2 µM final concentration. After a 30-min incubation at 37°C, T cells were washed and incubated with 10 µg/ml FITC-conjugated goat anti-human IgG Fc-specific Ab (Jackson ImmunoResearch Laboratories, West Grove, PA) for 20 min on ice. Fluorescence was detected using a FACScan flow cytometer (BD Biosciences).
Cell adhesion assays
Flat-bottom Immulon-1 96-well plates (Dynex Technologies) were precoated with 50 µl dICAM-1Fc (3 µg/ml) in PBS overnight and blocked with 2.5% BSA. A total of 2 x 105 T cells, labeled with 2.5 µM 2',7'-bis-(carboxyethyl)-5(6')-carboxyfluorescein, were treated with either 0–5 mM Mg2+/1 mM EGTA or Ca2+ and Mg2+ (0.4 mM) plus CD3 mAb UCHT1 (10 µg/ml) in 100 µl of assay buffer. Cytochalasin D, latrunculin A, and jasplakinolide, diluted appropriately from stock solutions, were added at the initiation of the experiment. Plates were incubated for 30 min at 37°C. Nonadherent T cells were removed, and adhesion was quantified using a Cytofluor multiwell plate reader series 4000 (PerSeptive Biosystems, Hertford, U.K.) and expressed as a percentage of the total emission before incubation.
Confocal microscopy
Thirteen-millileter round glass coverslips were precoated with 400 µl of dICAM-1Fc (3 µg/ml) or non-function-blocking LFA-1 mAb G25.2 at 10 µg/ml overnight at 4°C. Coverslips were blocked with 400 µl of 2.5% BSA in PBS for 1 h at 37°C. Additional coverslips were coated with 400 µl of 0.01% poly-L-lysine (PLL; Sigma-Aldrich) for 5 min followed by washing in RPMI 1640 and allowed to air dry for 2 h.
T cells (2 x 105 per coverslip) were incubated for 30 min at 37°C in 400 µl of assay buffer, including 5 mM Mg2+ and 1 mM EGTA. In addition, dICAM-1Fc (0.4–2 µM) was added in solution where indicated. To stain intracellular F-actin, 3% formaldehyde-fixed cells were permeabilized with 0.2% Triton X-100 (Sigma-Aldrich) and incubated with 7.5 µg/ml TRITC-conjugated phalloidin or 0.18 µg/ml Alexa Fluor 488-phalloidin for 20 min. Confocal microscopy was performed using a Zeiss laser scanning microscope LSM 510 equipped with a x63 oil immersion objective (Zeiss, Oberkochen, Germany). Images were collected as horizontal sections (x-y plane) taken at 0.5-µm intervals through whole cell volumes and were displayed either as a single mid-cell volume sections or as a projection along the z-axis. A palette display colored areas of each cell according to total fluorescence from red (brightest fluorescence) to blue (weakest fluorescence).
Detection of F-actin by laser scanning cytometry
The laser scanning cytometer (CompuCyte, Cambridge, MA) combines features of both flow and image cytometers (10, 11), in that it measures fluorescence and light scatter from immobilized cells that are moved through a 488-nm laser line on a motorized stage. T cells, mounted on coverslips as for confocal microscopy, were defined on the basis of their fluorescence as determined by Alexa Fluor 488-phalloidin-stained F-actin, and the threshold level was optimized so that as many single cells as possible could be contoured without losing fluorescence information. For each cell-contoured event, the following parameters were measured: 1) the area, which represents the physical area in square micrometers occupied by the contoured cell; 2) the integral fluorescence, which is the total amount of fluorescence from all the pixels within a defined cell contour; and 3) the maximum pixel, which is the level of fluorescence of the brightest pixel within the contoured area. Between 5000 and 8000 cells were measured per coverslip. The data were analyzed using an unpaired Student t test, and a value of p < 0.05 was taken as significant.
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Integrins such as LFA-1 require divalent cations for optimal
activity. In this study we have taken advantage of the ability of the
divalent cation Mg2+ with EGTA to activate
LFA-1-induced adhesion to ligand dICAM-1Fc (8, 9). This
procedure brings about direct changes to the LFA-1 ectodomain, enabling
higher-avidity binding to soluble dICAM-1Fc. Therefore, T cells that
were treated with 5 mM Mg2+/1 mM EGTA bound
dICAM-1Fc in solution, and this binding was inhibited by the
LFA-1-blocking mAb 38 (Fig. 1
A). It is relevant to note
that the T cells did not express FcRI (mAb 10.1), FcRII (mAb FL18.2),
or FcRIII (mAb 3G8) (n = 2–4; M. Robinson and N. Hogg,
unpublished observation), making it unlikely that FcR contributed to
the dICAM-1Fc binding. The level of soluble dICAM-1Fc bound to T cells
correlated directly with the concentration of
Mg2+ between 1 and 5 mM with no binding in the
absence of Mg2+ (data not shown). Cytochalasin D
(2 µM), an inhibitor of F-actin polymerization, had no effect on
binding of soluble dICAM-1Fc (Fig. 1A). This demonstrates
that Mg2+/EGTA directly altered the LFA-1
ectodomain, enabling binding to soluble ligand in a manner that had no
dependence on intracellular events associated with the
cytoskeleton.
|
The adhesion of Mg2+/EGTA-stimulated T cells
to immobilized dICAM-1Fc was also detected over a range of
Mg2+ concentrations, but adhesion was inhibited
by cytochalasin D (Fig. 1
B). Therefore, even when LFA-1 is
converted to higher-avidity form by exposure to
Mg2+/EGTA, cytoskeletal remodeling is an
essential component of T cell adhesion to immobilized dICAM-1Fc.
LFA-1-mediated adhesion can also be induced by signaling through
receptor complexes, such as TCR/CD3, and, following such
"inside-out" signaling, this adhesion was also blocked by
cytochalasin D (Fig. 1B) (12, 13). Thus, when
signals are delivered both from inside and outside the cell, the
cytoskeleton plays a role in LFA-1-mediated T cell adhesion to
immobilized ligand.
Cytochalasin D caps the barbed ends of F-actin filaments and prevents
their lengthening (14); however, other actin-binding drugs
have different modes of action. Both latrunculin A, which blocks
polymerization of monomeric G to F-actin (15), and
jasplakinolide, which stabilizes preexisting F-actin by inhibiting
depolymerization (16), prevented LFA-1-mediated adhesion
to dICAM-1Fc (Fig. 1, C and D). The finding that
three drugs with distinct effects on the cytoskeleton all interfere
with LFA-1-mediated adhesion emphasizes a requirement during the
process of adhesion for a dynamic cytoskeleton with necessity for both
actin depolymerization and actin repolymerization.
T cell adhesion to dICAM-1Fc causes F-actin bundle formation
These results suggested that high-avidity LFA-1, upon interaction
with ICAM-1, was able to directly remodel the actin cytoskeleton. Using
confocal microscopy, we examined the distribution of F-actin during T
cell adhesion. First, control T cells adhered to PLL were of rounded
morphology with low levels of F-actin when stimulated either without
(98.1 ± 0.1%; n = 3; Fig. 2, A and B) or with
Mg2+/EGTA (96 ± 0.2%; n =
3; Fig. 2, C and D). In contrast,
Mg2+/EGTA-stimulated T cells adherent to
dICAM-1Fc had discrete areas with high concentrations of F-actin
aggregates or bundles (Fig. 2, E and F). In
addition, a majority of T cells (75.8 ± 2.1%; n
= 3) had a dramatically altered morphology, with many T cells
displaying irregularly arranged filopodia-like processes emanating from
the cell body. Thus, LFA-1-mediated adhesion of T cells to immobilized
dICAM-1Fc provided the stimulus for F-actin bundle formation and a
distinctive shape change.
|
, and the average contoured
areas of the adhered cells were 201 ± 18
µm2 (PLL), 199 ± 14
µm2 (PLL/Mg2+/EGTA), and
241 ± 5 µm2
(dICAM-1Fc/Mg2+/EGTA). Thus, the cells that were
spread on dICAM-1Fc covered 
20% more surface area, in keeping with
their elongated shape. To test whether the increase in F-actin bundles,
as observed by microscopy, was a general one, the T cells were first
compared for the fluorescence levels of localized F-actin (maximum
pixel or brightness of F-actin bundles) using laser scanning cytometry.
A gate was set to include the majority of the PLL control T cell
population (Fig. 3A). When
dICAM-1Fc/Mg2+/EGTA-treated T cells were compared
with either the PLL- or PLL/Mg2+/EGTA-treated
cells, a larger proportion had brighter levels of fluorescence (35.5 vs
7.1 and 6.8%, respectively) (Fig. 3, A–C) and a
2-fold overall increase in fluorescence (data not shown). Therefore,
exposure to immobilized dICAM-1Fc caused new F-actin bundle formation
in 30% of these primary T cells above the control levels.
|
, D–F), indicating an increase in F-actin
polymerization for these cells (overall 2-fold increase in arbitrary
fluorescence units; data not shown). The close correlation between
total fluorescence and maximal brightness of F-actin per T cell (Fig. 3, G–I) suggested that the newly polymerized
F-actin was associated with a dynamic conversion to higher-order
F-actin bundles and that this process was substantially increased by
LFA-1 binding to dICAM-1Fc. LFA-1 clustering and high avidity are essential for F-actin bundling and polymerization
We next investigated those properties of LFA-1 necessary for
driving the cytoskeletal rearrangements, in particular whether
clustering of LFA-1 was involved. T cells were immobilized with no
Mg2+ treatment on PLL or non-function-blocking
LFA-1 mAb G25.2 and F-actin levels compared by laser scanning
cytometry. Increased levels of both overall fluorescence (integral) and
localized fluorescence (maximum pixels) of the F-actin bundles was
associated with the mAb G25.2-treated T cells compared with the
PLL-bound T cells (Table I), indicating
that LFA-1 clustering was promoting F-actin remodeling. These increases
were evident in 23% (total fluorescence) and 17% (maximum pixel) more
G25.2 than PLL-tethered T cells, respectively.
|
). The same
situation prevailed even when mAb G25.2 was titrated down to levels
supporting less than maximum levels of tethering (<1 µg/ml) (data
not shown).
Next, confocal microscopy was used to compare
Mg2+/EGTA-treated T cells that were tethered on
mAb G25.2 or PLL or allowed to bind to dICAM-1Fc. The F-actin content
of the mAb G 25.2-bound cells resembled the dICAM-1-adhering cells,
confirming the laser scanning cytometry results (Fig. 4). Together the findings indicate
clustering is essential for the LFA-1-mediated signaling leading to
F-actin formation. However, conformationally altered integrin is also
required, as tethering of T cells without
Mg2+/EGTA treatment causes much less F-actin
polymerization and bundling.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The two components of integrin clustering and conformational change
have a role in the LFA-1-mediated changes, leading to a maximal
increase and remodeling of F-actin. It may be important to provide a
framework of clustered active integrin mediating the appropriate
signals to build an intracellular F-actin cytoskeletal network. These
findings are reminiscent of integrin
51-mediated signaling
in which clustering and exposure of this integrin to ligand mimetic
caused F-actin and cytoskeletal-associated proteins to collect around
fibronectin-coated beads (1). However, different integrins
may use alternative mechanisms to connect to the cytoskeletal machinery
of the cell. There is evidence that, in fibroblasts,
integrin-containing focal adhesions couple to the preformed
cytoskeletal network upon contacting ligand (2, 20).
It is interesting that the addition of soluble dICAM-1Fc had no extra effect on the Mg2+/EGTA-induced high-avidity conformation of LFA-1 in terms of F-actin generation. The presumption is that the presence of excess bound metal ion performs the same role as ligand in either stabilizing or altering integrin conformation. This has been previously demonstrated for both Mg2+/EGTA (9) and Mn2+ (21) in terms of eliciting expression of integrin activation epitopes. As activated integrin seems instrumental in generating most of the potential F-actin increase, in the situation where F-actin formation occurs in the presence of LFA-1 mAb alone, a smaller reservoir of active LFA-1 receptors may already be expressed by the T cells. In vivo, it is likely that ICAM-1 on the target cell, by interacting with LFA-1, would have a role in promoting these changes in F-actin that we have induced with Mg2+/EGTA. ICAM-1 is expressed as a dimeric molecule (22, 23) and, on activated endothelium, can be found in leukocyte-induced clusters (24). Thus, ICAM-1 and LFA-1 could promote mutual clustering. Clustering would provide the means of localizing active integrins, thereby increasing the collective signal necessary to generate and remodel the F-actin network.
In this work we have focused on a functional end point of the signaling
stimulated by LFA-1. An exciting future prospect will be to determine
the individual components of the LFA-1-mediated signaling pathway(s)
leading to F-actin formation. LFA-1 has been implicated in the
phosphorylation of phospholipase-
1 (25), focal adhesion
kinase, and proline-rich tyrosine kinase-2 (26) and
in the protein kinase C I translocation to the microtubule network
(27). These latter kinases are apparently more involved in
microtubule than in F-actin reorganization.
In more physiological circumstances, inside-out signals can cause LFA-1 to cluster (7). The cause of the LFA-1 conformational change which leads to affinity increase is less certain, but one study has demonstrated that chemokines cause a transient affinity increase in LFA-1 (28). Thus, signals received by the T cells during an immune response could provide the necessary triggers for both integrin clustering and avidity/affinity changes essential for the F-actin remodeling. The fact that LFA-1 is made active through inside-out signaling suggests that signals from LFA-1 are most effective within the context of activities dictated by other classes of receptor. Thus, signals delivered by chemokines, for example, may direct the spatial distribution of F-actin polymerization observed in chemotaxing leukocytes (29). Another situation is at the immunological synapse formed between T cells and Ag-presenting surfaces, where LFA-1 provides an adhesive contact zone surrounding the Ag-specific TCR (6). It is possible that localized remodeling of the cytoskeleton by LFA-1 at this interface between T cells and target might serve as a scaffold for other signaling molecules or perhaps modulate the movement of other receptors at this dynamic surface. Of course, cytoskeletal remodeling may well occur by signaling through other receptors, such as the TCR (30), although in such studies no account has been taken of a potential contribution from integrins. Finally, the fact that LFA-1 signals to the cytoskeleton in T cells contributes to an evolving awareness of the complexity and specificity of integrin signaling in which these receptors can now claim a much greater role than the purely adhesive.
|
Acknowledgments |
|---|
|
Footnotes |
|---|
2 Address correspondence and reprint requests to Dr. Nancy Hogg, Leukocyte Adhesion Laboratory, Cancer Research U.K. London Research Institute, 44 Lincoln’s Inn Fields, London WC2A 3PX, U.K. E-mail address: nancy.hogg{at}cancer.org.uk
3 Abbreviations used in this paper: F-actin, filamentous actin; dICAM, dimeric ICAM; PLL, poly-L-lysine.
Received for publication February 19, 2002. Accepted for publication April 3, 2002.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
1 integrins on fibroblasts. Nature 383:438.[Medline]
41 integrin-dependent cell adhesion is regulated by a low affinity receptor pool that is conformationally responsive to ligand. J. Biol. Chem. 270:28740.2-integrin LFA-1 signaling through phospholipase C-1 activation. Proc. Natl. Acad. Sci. USA 90:7099.(I) in LFA-1-mediated locomotion of activated T cells. Nat. Immunol. 2:508.[Medline]
2 integrin affinity and mobility changes: differential regulation and roles in lymphocyte arrest under flow. Immunity 13:759.[Medline]
This article has been cited by other articles:
|
|
 |
|
  R. Evans, I. Patzak, L. Svensson, K. De Filippo, K. Jones, A. McDowall, and N. Hogg Integrins in immunity J. Cell Sci., January 15, 2009; 122(2): 215 - 225. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. R. Sarantos, H. Zhang, U. Y. Schaff, N. Dixit, H. N. Hayenga, C. A. Lowell, and S. I. Simon Transmigration of Neutrophils across Inflamed Endothelium Is Signaled through LFA-1 and Src Family Kinase J. Immunol., December 15, 2008; 181(12): 8660 - 8669. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Z. Jevnikar, N. Obermajer, M. Bogyo, and J. Kos The role of cathepsin X in the migration and invasiveness of T lymphocytes J. Cell Sci., August 15, 2008; 121(16): 2652 - 2661. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Jolly, I. Mitar, and Q. J. Sattentau Adhesion Molecule Interactions Facilitate Human Immunodeficiency Virus Type 1-Induced Virological Synapse Formation between T Cells J. Virol., December 15, 2007; 81(24): 13916 - 13921. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. Castriconi, A. Dondero, C. Cantoni, M. Della Chiesa, C. Prato, M. Nanni, M. Fiorini, L. Notarangelo, S. Parolini, L. Moretta, et al. Functional characterization of natural killer cells in type I leukocyte adhesion deficiency Blood, June 1, 2007; 109(11): 4873 - 4881. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J.-i. Suzuki, S. Yamasaki, J. Wu, G. A. Koretzky, and T. Saito The actin cloud induced by LFA-1-mediated outside-in signals lowers the threshold for T-cell activation Blood, January 1, 2007; 109(1): 168 - 175. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 X. Chen, D. S. J. Allan, K. Krzewski, B. Ge, H. Kopcow, and J. L. Strominger CD28-stimulated ERK2 phosphorylation is required for polarization of the microtubule organizing center and granules in YTS NK cells PNAS, July 5, 2006; 103(27): 10346 - 10351. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. E. Green, U. Y. Schaff, M. R. Sarantos, A. F. H. Lum, D. E. Staunton, and S. I. Simon Dynamic shifts in LFA-1 affinity regulate neutrophil rolling, arrest, and transmigration on inflamed endothelium Blood, March 1, 2006; 107(5): 2101 - 2111. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. R. Tardif and M. J. Tremblay LFA-1 Is a Key Determinant for Preferential Infection of Memory CD4+ T Cells by Human Immunodeficiency Virus Type 1 J. Virol., November 1, 2005; 79(21): 13714 - 13724. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. N. Atapattu and C. J. Czuprynski Mannheimia haemolytica Leukotoxin Induces Apoptosis of Bovine Lymphoblastoid Cells (BL-3) via a Caspase-9-Dependent Mitochondrial Pathway Infect. Immun., September 1, 2005; 73(9): 5504 - 5513. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. Parameswaran, R. Suresh, V. Bal, S. Rath, and A. George Lack of ICAM-1 on APCs during T Cell Priming Leads to Poor Generation of Central Memory Cells J. Immunol., August 15, 2005; 175(4): 2201 - 2211. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. R. Tardif and M. J. Tremblay Regulation of LFA-1 Activity through Cytoskeleton Remodeling and Signaling Components Modulates the Efficiency of HIV Type-1 Entry in Activated CD4+ T Lymphocytes J. Immunol., July 15, 2005; 175(2): 926 - 935. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. F. Barber, M. Faure, and E. O. Long LFA-1 Contributes an Early Signal for NK Cell Cytotoxicity J. Immunol., September 15, 2004; 173(6): 3653 - 3659. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K. J. Ralston, S. L. Hird, X. Zhang, J. L. Scott, B. Jin, R. F. Thorne, M. C. Berndt, A. W. Boyd, and G. F. Burns The LFA-1-associated Molecule PTA-1 (CD226) on T Cells Forms a Dynamic Molecular Complex with Protein 4.1G and Human Discs Large J. Biol. Chem., August 6, 2004; 279(32): 33816 - 33828. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. D. van Buul and P. L. Hordijk Signaling in Leukocyte Transendothelial Migration Arterioscler. Thromb. Vasc. Biol., May 1, 2004; 24(5): 824 - 833. [Abstract] [Full Text]
|
|
|
|
|
|
L. Sanchez-Martin, N. Sanchez-Sanchez, M. D. Gutierrez-Lopez, A. I. Rojo, M. Vicente-Manzanares, M. J. Perez-Alvarez, P. Sanchez-Mateos, X. R. Bustelo, A. Cuadrado, F. Sanchez-Madrid, et al. Signaling through the Leukocyte Integrin LFA-1 in T Cells Induces a Transient Activation of Rac-1 That Is Regulated by Vav and PI3K/Akt-1 J. Biol. Chem., April 16, 2004; 279(16): 16194 - 16205. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. Hogg, M. Laschinger, K. Giles, and A. McDowall T-cell integrins: more than just sticking points J. Cell Sci., December 1, 2003; 116(23): 4695 - 4705. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. R. Tardif and M. J. Tremblay Presence of Host ICAM-1 in Human Immunodeficiency Virus Type 1 Virions Increases Productive Infection of CD4+ T Lymphocytes by Favoring Cytosolic Delivery of Viral Material J. Virol., November 15, 2003; 77(22): 12299 - 12309. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. Tskvitaria-Fuller, A. L. Rozelle, H. L. Yin, and C. Wulfing Regulation of Sustained Actin Dynamics by the TCR and Costimulation as a Mechanism of Receptor Localization J. Immunol., September 1, 2003; 171(5): 2287 - 2295. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. Riteau, D. F. Barber, and E. O. Long Vav1 Phosphorylation Is Induced by {beta}2 Integrin Engagement on Natural Killer Cells Upstream of Actin Cytoskeleton and Lipid Raft Reorganization J. Exp. Med., August 4, 2003; 198(3): 469 - 474. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Smith, M. Bracke, B. Leitinger, J. C. Porter, and N. Hogg LFA-1-induced T cell migration on ICAM-1 involves regulation of MLCK-mediated attachment and ROCK-dependent detachment J. Cell Sci., August 1, 2003; 116(15): 3123 - 3133. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. G. Yipp, S. M. Robbins, M. E. Resek, D. I. Baruch, S. Looareesuwan, and M. Ho Src-family kinase signaling modulates the adhesion of Plasmodium falciparum on human microvascular endothelium under flow Blood, April 1, 2003; 101(7): 2850 - 2857. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. E. Greening, T. I.M. Tree, K. T. Kotowicz, A. G. van Halteren, B. O. Roep, N. J. Klein, and M. Peakman Processing and Presentation of the Islet Autoantigen GAD by Vascular Endothelial Cells Promotes Transmigration of Autoreactive T-Cells Diabetes, March 1, 2003; 52(3): 717 - 725. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. P. Mizgerd, M. R. Spieker, and M. M. Lupa Exon truncation by alternative splicing of murine ICAM-1 Physiol Genomics, December 26, 2002; 12(1): 47 - 51. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
