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on T Cell Rolling and Tight Adhesion to Monolayers of Activated Endothelial Cells1
Veterinary Molecular Biology, Montana State University, Bozeman, MT 59717
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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(SDF-1) has been
shown to induce tight adhesion of T cells to purified ICAM-1 in assays
done under flow conditions. In this study, we show that soluble
SDF-1 induced a rapid (within 20 s) cessation of rolling and
tight adhesion of >90% of the rolling T cells on monolayers of
activated endothelial cells under similar flow. Within 4 min, the T
cells had either started to migrate between the endothelial cells or
re-entered the rolling and circulating lymphocyte pool. This
deadherence of the firmly bound cells, with either ensuing
transmigration or continued rolling, was most likely due to
desensitization of lymphocytes to the continuously present SDF-1.
The released rolling lymphocytes could still respond to other
activating signals by a second round of tight adhesion. Pretreating the
lymphocytes with pertussis toxin almost completely blocked the effect
of the chemokine, confirming that the induction of firm adhesion was
due to the function of the chemokine on the lymphocytes and not the
endothelial cells. Pretreating the endothelium with SDF-1 did not
lead to firm adhesion of subsequently added lymphocytes, also
indicating that the effect was due to soluble, not endothelially bound,
chemokine. Blocking experiments showed that the same molecules mediated
rolling before and after SDF-1-induced tight adhesion. This is the
first study to demonstrate the effect of soluble SDF-1 on T cell
rolling on an endothelial cell monolayer. The data broaden our
understanding of the stimulatory factors directing the firm adhesion
and ensuing transmigration of leukocytes into tissues through activated
endothelium. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Characterization of the molecular pathways involved in rapid adhesion
following initiation of rolling has received considerable attention in
recent years and is well understood for myeloid cells
(6, 7, 8, 9). Soluble chemotactic factors (chemokines) trigger a
rapid transition of rolling neutrophils to tightly adhered ones in
assays done under physiological flow (6, 9). Chemokines
have also been shown to increase lymphocyte adhesion
(10, 11, 12). In an elegant study, Campbell et al.
(10) showed that stromal cell-derived factor 1
(SDF-1),3 6-C-kine,
and macrophage-inflammatory protein-3ß trigger rapid arrest of
lymphocytes rolling on purified peripheral node addressin (PNAd) to
ICAM-1 coated on the same substrate. Induction of tight adhesion was
triggered by immobilizing the chemokine on the same substrate as PNAd
and ICAM-1. Pachynski et al. (11) used very similar
experimental conditions to show that 6-C-kine (secondary
lymphoid-tissue chemokine) triggers rapid adhesion of lymphocytes to
recombinant mucosal addressin cell adhesion molecule-1. Piali et al.
(12), on the other hand, stimulated HUVECs with IFN-
and TNF- and found firm adhesion of incoming lymphocytes in a
parallel plate flow assay . This firm adhesion was likely due to the
chemokines IFN- induced protein-10 (IP10) and monokine induced by
IFN- (Mig) produced by the endothelial cells.
Although the results outlined above are quite compelling, they do not directly address whether the addition of soluble chemokine induces rapid adhesion under flow. Another important aspect not covered by these studies is what happens to the rolling lymphocytes upon continual exposure to a chemokine. Desensitization of leukocytes to a chemokine has been shown both in firm adhesion of IL-8RA-transfected cells to purified ICAM-1 and IL-8 under flow (13), with IP10 and Mig on immobilized ICAM-1 in a static assay (12) and in chemotaxis assays (14). The latter study also showed that the capacity to respond to other chemotactic factors was retained by the desensitized leukocytes that no longer respond to the original chemokine. Finally, chemokines induce rapid adhesion to an artificial substrate of purified ligands, but what are the consequences of exposure of soluble chemokine to lymphocytes rolling on the complex surface of the vascular endothelium under continuous flow?
In this study, we demonstrate that soluble SDF-1, when injected into
an assay with lymphocytes rolling on an endothelial cell monolayer
under continuous flow, induces rapid, transient adhesion of the rolling
lymphocytes. Under the continual presence of the chemokine the
deadhered and thus desensitized cells are still capable of firm
adhesion upon addition of other stimulants. The molecular mediators of
rolling in the desensitized cells and the leukocytes before firm
adhesion were similar. These findings emphasize the importance of
desensitization to chemokines in lymphocyte homing.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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T cell purification
Heparinized peripheral blood from 1-wk to 3-mo-old male calves
was collected, diluted 1:1 with warm HBSS, and centrifuged through
Histopaque 1077 (Sigma, St. Louis, MO) at 800 x g for
30 min at room temperature. Mononuclear cells were collected from the
Histopaque/plasma interface. Monocytes were removed by adhesion to
plastic, and T cells were purified by panning on monolayers of
E-selectin cDNA-transfected L cells. After a 30-min incubation at
37°C, the T cells were collected by incubation with 2 mM EDTA,
yielding >90% of T cells (Ref. 15 and our
unpublished data).
Transmigration assay
Purified T cells were transferred into the upper wells of
3-µm pore 6-well transwell plates (Becton Dickinson Labware, Franklin
Lakes, NJ). The cells were allowed to migrate for 4 h at 37°C
passively or after the addition of 200 ng/ml of SDF-1 (PeproTech,
Rocky Hill, NJ) to the lower well. The migrated cells were collected
and the T cells were enumerated with a hemocytometer and FACS
analysis of the GD3.8+ (pan- T cell marker;
(16)) lymphocytes identified by their distinctive light
scatter profile.
Rolling assay
To address the effect of the continuous exposure to a soluble
chemokine and possible desensitization, a system in which the rolling
of unactivated lymphocytes on endothelial cell monolayers can be
reproducibly analyzed over extended periods of time is required. We
have previously defined an in vitro system using stimulated endothelial
cells grown on the internal surface of glass capillary tubes as the
adhesive substrate and bovine peripheral blood T cells as the
rolling lymphocyte population (15). The assay employs a
circulatory loop; thus, the same population of lymphocytes can be
continuously monitored over time. Also, a chemokine added into this
assay is continuously presented to the cells. The bovine T cell
population can be purified in large numbers and, by isolating the cells
from newborn animals, they are homogeneously in an unactivated state.
As such, unless an additional stimulus is added to the rolling assays,
bovine T cells continuously roll on activated endothelial cells
for up to 1 h. Importantly, in this system the receptor-ligand
interaction involved in rolling does not induce signaling, leading to
firm attachment of the lymphocytes.
For the current study, this previously published capillary tube
shear-dependent rolling assay was modified slightly (15).
Bovine umbilical cord endothelial cells were grown to confluency on the
internal surface of sterile 1.4-mm capillary tubes (Drummond
Scientific, Broomall, PA) and stimulated with 50–100 ng of LPS for
4–5 h at 37°C to induce expression of endothelial adhesion
molecules. Tubing was attached to each end of the capillary tube to
form a closed circulatory system. Within this system, fluid and cells
were recirculated by using a variable peristaltic pump (Cole Parmer,
Barrington, IL). The capillary tube was mounted on an inverted
microscope (Nikon Diaphot; Nikon, Tokyo, Japan) modified for video
microscopy (Sony CDD Camera, Sony, Tokyo, Japan). The enriched T
cells were incubated for 2–3 h at 37°C and injected into the system
at 1–2 x 106 cells/ml in DMEM with 10%
FBS and 20 mM HEPES. SDF-1 (2–40 ng/ml) was added to the assay at
time points indicated in the
Figs. 1–5
. Each lot of SDF-1 used in
the study was tested for activity in the chemotaxis assay, aliquoted,
and stored at -80°C until they were used. In some experiments, PMA
(100 ng/ml) was added to the assay. To further characterize the effect
of SDF-1, pertussis toxin (PTX; 100 ng/ml) was used to pretreat the
lymphocytes for 2 h at 37°C (17). The time needed
for the chemokine to disperse throughout the flow system was about
7 s (data not shown). The camera was focused on a field supporting
rolling under a shear force of 
2 dynes/cm2,
and the same field was monitored throughout the assay. The number of
rolling and firmly adhered T cells within this field of view was
determined by analysis of the videotape recording with a macrodriven
NIH Image software on a Macintosh 660 AV computer (Apple, Cupertino,
CA). Aggregates were excluded from the analyses.
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T cell rolling on 24-h LPS-activated endothelial cells
(15), or a non-blocking E-selectin recognizing mAb EL-81
were injected into the assay at 50 µg/ml for each mAb. |
Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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cross-reacts with bovine T cells
An in vitro chemotaxis assay was used to test whether human
SDF-1 cross-reacts with bovine T cells. As shown in Fig. 1
, SDF-1 at a concentration of 200
ng/ml induced chemotaxis of purified bovine T cells in a
micropore filter assay. In preliminary experiments, the migratory
response of bovine lymphocytes was detectable at 50 ng/ml, peaked
around 200 ng/ml, and decreased with doses of 400 ng/ml or higher (data
not shown). When compared with passive migration, the proportion of
T cells migrating from the upper to the lower chamber increased
26-fold when SDF-1 was applied to the lower chamber. When SDF-1
was added to the top chamber with the lymphocytes, thus eliminating the
concentration gradient and desensitizing the cells to SDF-1, the
number of lymphocytes migrating through the filter decreased to about
20% of the passively migrating cells (data not shown). Thus, human
SDF-1 is chemotactic for bovine T cells.
SDF-1 induces a rapid, transient adhesion of rolling cells to an
endothelial cell monolayer
Next, we tested whether SDF-1 could induce rapid adhesion of
rolling cells in the capillary tube assay. Rolling of enriched T
cells on the LPS-stimulated endothelial cells under continuous flow was
established as described in Materials and Methods. As shown
in Fig. 2A, T cells
continuously rolled in this assay for over 20 min, with minimal tight
adherence to the endothelial cell monolayer. When PMA was infused in
the assay, adhesion occurred within 2 min and the cells remained
attached for more than 30 min (data not shown; see Fig. 3). As shown in Fig. 2B,
within 20 s of injecting 20 ng/ml of SDF-1 into the assay,
>90% of the rolling cells completely stopped on the endothelial cell
monolayer. The bound cells remained tightly adhered for 2–4 min, some
flattened and began to migrate in between the endothelial cells,
whereas others eventually detached and re-entered the circulation. Once
the T cells released and re-entered the circulation, most of them
immediately began to roll on the endothelial cell monolayer in the
continual presence of activating concentrations of SDF-1. Thus, they
rapidly became desensitized to the induction of firm adhesion by the
chemokines. In control experiments, a second injection of SDF-1
following the deadhesion of the adhered cells did not cause new firm
adhesion of the cells (data not shown), also speaking for the
desensitization of the released cells.
Interestingly, the number of cells rolling after the transient firm
adhesion of some of the lymphocytes was higher than before the addition
of the chemokine (Fig. 2B). To test whether the rerolling
lymphocytes could respond to other potential signaling molecules and
reinitiate tight adhesion, PMA was injected into the assay. As shown in
Fig. 2C, PMA caused a rapid induction of tight adhesion of
the lymphocytes.
To study further the sensitization and desensitization events that
occurred following injection of SDF-1 into the rolling assay, a
sequential dose-response analysis was done. Rolling interactions were
established, as described for Fig. 2, and then SDF-1 was injected at
2 ng/ml, which led to variable induction of firm adhesion, ranging from
5 to 50% of the cells in the field of view. In experiments in which
significant tight adhesion was induced (approaching 50% of the rolling
cells), deadhesion and rerolling occurred in the same fashion as shown
in Fig. 2B (data not shown). In experiments in which 2 ng/ml
of SDF-1 induced minimal tight adhesion without a reduction of
rolling, a second injection of 20 ng/ml of SDF-1 led (Fig. 4) to a rapid induction of tight adhesion
and reduction in rolling as seen in Fig. 2B. Thus,
sensitization and desensitization was dose dependent, with 2 ng/ml of
SDF-1 being at the lower threshold needed to induce the effects.
Pretreatment of lymphocytes with PTX blocks SDF-1-induced firm
adhesion
Chemokine signaling has, in many cases, been shown to be mediated
through Gi-linked receptors (10, 11). PTX blocks this signal transduction pathway by inactivating
Gi proteins. The effect of SDF-1 was almost
completely blocked by pretreatment of the lymphocytes with PTX (Fig. 3). The treatment with PTX, however, did not prevent the capability of
the cells to firmly bind to the endothelium, since the addition of PMA
to the assay still induced firm binding of the cells. The effect of PTX
also showed that the effect of the chemokine under these conditions is
most crucial for the lymphocytes, not for the endothelial cells.
Endothelial cells do not present previously bound SDF-1 to the rolling cells
Chemokines have been shown to bind to endothelial cell
proteoglycan (19, 20), which contributes to the
presentation of the chemokine to the leukocytes. To determine whether
the activated endothelial cells used in our rolling assay participated
in the induction of firm adhesion, we injected the chemokine into the
assay before the addition of the T cells and allowed it to
interact with the endothelial cells for 7–8 min under flow conditions.
The tubing was washed by injecting 30 ml of fresh media through the
tubing at approximately the same flow rate as in the rolling assay. The
T cells were then added to the assay. Induction of tight
adhesion was not seen, the T cells continually rolled as in the
injection of cells to an assay before the addition of the chemokine
(Fig. 5). The addition of SDF-1 into
the assay induced firm adhesion of the cells, thus confirming that the
injected cells were capable of responding to SDF-1 (Fig. 5). The
fact that, upon injection of SDF-1 to the assay with rolling
lymphocytes, a single wave of firm adhesion was seen showed that the
soluble chemokine controls the formation of firm adhesion in this
assay.
The same adhesion molecules support lymphocyte rolling before and
after SDF-1-induced firm adhesion
The rolling of leukocytes on endothelial cells has been shown to
be mediated by multiple adhesion molecules including selectins,
4 integrins, and CD44 (for a review, see Ref.
5). To study whether the desensitized cells utilized the
same adhesion molecules in their rolling as before the addition of the
chemokine, we used E-selectin cDNA-transfected L cells to support
T cell rolling as described previously (18). This
approach limits rolling to a single molecule. Enriched T cells
were allowed to roll on the transfectants, and after the addition of
SDF-1, firm adhesion of the rolling cells to the L cells was induced
(data not shown). As compared with the effect of SDF-1 on T
cells rolling on activated endothelial cells, induction of firm
adhesion to the L cells was slower (peak accumulation at 8–10 min) and
involved a smaller proportion of the rolling cells (
15% vs >90%).
As published earlier, this rolling could be blocked by the addition of
EL-246 into the assay (18). Also, when EL-246 was injected
into the assay after SDF-1 when the desensitized cells continued to
roll, virtually all rolling was inhibited within 2 min upon the
addition of the mAb (data not shown). In Ab-blocking experiments on
bovine endothelial cells, >90% of T cell rolling is blocked
within 3 min by the mAb GR113, whereas control mAb EL-81 and EL-246
have no effect (see fig. 1A in Ref. 15). When
GR113 was injected into the T cell/endothelial cell rolling
assay after the desensitization of the lymphocytes to SDF-1,
similarly almost all rolling was prevented (Fig. 5). Thus, lymphocytes
that become desensitized to SDF-1 retain the capacity to roll on the
same molecule as they did before SDF-1 treatment.
Rolling speeds of adhering cells are heterogeneous
The rolling speeds of the T cells were heterogeneous
(10.9 ± 5.3 µm/s in a representative experiment,
n = 64 cells). Also, the rolling speeds of the cells
before the induction of firm adhesion showed variation, some cells
rolling and then skipping up to 50 µm before firmly adhering, some
rolling continuously until adhering, and some slowing their rolling
speed just before stopping (data not shown). By comparison, the rolling
speed on E-selectin-transfected L cells was slower (6.0 ± 7.3
µm/s; n = 20). Thus, a specified rolling velocity did
not seem to be a prerequisite for firm adhesion.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Leukocyte subsets have the capacity to respond to a multitude of
chemokines and/or chemotactic factors (14). Furthermore,
many of these factors of leukocyte migration may be concomitantly
present in tissues recruiting leukocytes. Recent studies have
demonstrated the simultaneous production of multiple chemokines by
stimulated endothelial cells (12, 20). Similarly, in an
infection and at sites of inflammation, chemoattractants are produced
by host endothelial, epithelial, and stromal cells and by activated
leukocytes within the tissue. Thus, the migrating lymphocytes encounter
a multitude of gradients of chemotactic factors. SDF-1 has been shown
to be a highly efficacious chemoattractant for human lymphocytes,
including both T cells (21) and B cells (22).
SDF-1 has two isoforms, SDF-1 and SDF-1ß, that differ from one
another by four additional amino acids on the carboxyl-terminal of the
latter (23). The genes of both SDF-1 isoforms and its only
known receptor, CXCR4, are all conserved in the human and mouse with
>90% similarity between the species (24, 25, 26, 27) and thus
made the experiments of cross-reactivity in bovine feasible.
This study shows that lymphocyte sensitization to SDF-1 followed by
desensitization can occur within minutes on the surface of the
endothelium, yet these cells can still respond to other activating
agents, leading to tight adhesion. This finding is of special
importance since it shows that desensitized cells are likely still able
to respond to other factors within the same or different tissues at the
vessel surface. The desensitization process is likely required for the
lymphocytes to release and migrate through the vessel or re-enter the
blood flow while continuously exposed to the original chemokine. The
multitude of chemotactic factors that exist in the body ensures that
once desensitization to one factor takes place, there are many others
that can regulate the subsequent steps of the extravasation process.
Together with the various patterns of adhesion molecules expressed by
lymphocyte subsets, chemokines, through sensitization, as originally
proposed, and now desensitization, as described here, provide exquisite
regulation of the multistep process of lymphocyte homing.
As compared with purified ligands, the endothelial cell monolayer used in our assay and the endothelium in vivo simultaneously provide various densities of multiple ligands for rolling and firm adhesion. Leukocyte subsets could show different usage of these ligands, possibly as a function of their status of activation. Furthermore, the firm adhesion of the first cells upon chemokine stimulus alters the adhesive potentials of the vascular cell wall by allowing leukocyte-leukocyte rolling. This could be one way of increasing the capacity of leukocytes to migrate into the tissue in vivo.
The chemotactic effects of chemokines are known to depend on
concentration gradients (14). On the other hand, some
chemokines have been shown to be presented by the endothelial
proteoglycans (19, 20) and to induce firm adhesion without
the formation of a gradient. In vivo, when chemokines are produced by
various cells in tissues and enter the vascular lumen, they are either
bound by the endothelium or enter the flow of blood. Both forms,
immobilized and soluble, have biological activity. For example, Weber
et al. (20) demonstrated stopping of rolling monocytes by
proteoglycan-bound growth-related oncogene and subsequent shape
changes by soluble monocyte chemoattractant protein-1 on
TNF--stimulated endothelial cells in assays done under flow. Firm
adhesion of rolling lymphocytes on endothelium has been previously
shown by Piali et al. (12), who found that stimulation of
the endothelial cells with IFN- and TNF- led to the production of
the chemokines IP10 and Mig, and that IL-2-stimulated T cells firmly
bound to these cells under flow conditions. By injecting the soluble
chemokine directly into the assay, the present study confirms that the
induction of firm adhesion by SDF-1 is due to the injected chemokine
and not other possible factors secreted by the stimulated endothelium.
Our findings suggest that neither a concentration gradient nor
endothelial presentation is required for SDF-1-induced firm
adhesion. Since a gradient is not required, soluble chemokine released
by the tissue could have biological significance at the vessel surface
with respect to inducing rapid tight adhesion of rolling lymphocytes.
In this setting, upon encountering a chemokine released in the blood at
a specific site on a vessel, the rolling lymphocyte will be continually
exposed to the chemokine as it is carried with the blood flow. The
rolling event, which greatly slows the movement of the lymphocyte
within the blood, likely provides a sufficient length of time for
exposure to induce tight adhesion (the chemokine acts within
seconds).
This study does not address the importance of SDF-1 in vivo, only
that a soluble chemokine can induce rapid tight adhesion of rolling
lymphocytes. However, as discussed by Bleul et al. (21),
SDF-1 is constitutively expressed in a broad range of tissues. It is
possible that soluble SDF-1 contributes to basal lymphocyte
migration into a variety of tissues. Furthermore, even though SDF-1
production is not increased in inflammation (21), it may
also contribute to the recruitment of inflammatory lymphocytes in some
tissues. In this setting, the inflammation-induced recruitment would be
controlled by the up-regulation of the adhesion molecules required for
rolling. Once rolling was initiated, lymphocytes could respond to the
basal levels of SDF-1.
A recent study by Derdeyn et al. (28) revealed significant
variation in the levels of SDF-1 in the blood of healthy
individuals. In 31 volunteers, the mean SDF-1 (±SD) concentration
was 25 ± 34.7 ng/ml, with a range of 0.28–106.5 ng/ml. It seems
plausible that the variation in our results with induction of firm
adhesion with the low doses (2 ng/ml) of SDF-1 could be a reflection
of similar interindividual variation in the levels of SDF-1 that each
animal’s cells were used to in the circulation. Thus, the lower dose
would show more variation, whereas the higher dose would be inducing
sensitization, and desensitization, of a higher proportion of the
cells. Also of importance is the cell surface expression of the CXCR4
receptor for SDF-1 that has been shown to be increased in short
periods of culture on human cells (29). Similarly, we have
found increased cell surface expression of CXCR4 on bovine lymphocytes
under conditions identical to those used to purify and pretreat the
cells in the current study (J. M. Kantele and M. A. Jutila,
manuscript in preparation). Thus, it is important to recognize that in
this study SDF-1 was used to induce firm adhesion to deepen our
understanding of the basic mechanisms of lymphocyte homing. The finding
that concentration levels lower than those found in vivo were able to
induce firm adhesion of the rolling cells could mean that at least part
of the leukocytes in the circulation could be desensitized to SDF-1.
This in turn could require changes in the cells’ expression of CXCR4
by other stimuli to make them responsive to SDF-1. However, we do
not know the amount of SDF-1 in the FBS that was a part of the media
in our assay nor whether the age of an animal would have an effect on
the circulatory levels of SDF-1.
The presence of multiple ligands for rolling presented by the
LPS-activated endothelial cells prompted the question whether the
mechanisms supporting rolling of lymphocytes before the addition of
SDF-1 and after their desensitization to the chemokine were the
same. To simplify this question, the assay was done with E-selectin
cDNA-transfected mouse L cells that had previously been shown to
support bovine T cell rolling (18). As on
endothelial cells, SDF-1 was able to induce firm adhesion of the
rolling lymphocytes. The finding of slower and less extensive binding
could be due to differences between the expressions of adhesion
molecules on the transfectants and the activated endothelial cells.
When the blocking experiments were repeated on activated endothelial
cells, the mAb GR113 was found to block the rolling of both
unstimulated and desensitized lymphocytes. Combined, these experiments
showed that T cell rolling was supported by similar mechanisms
before and after SDF-1-induced firm adhesion of the lymphocytes.
Strikingly, the number of rolling cells increased after the peak
response of firm adhesion following injection of SDF-1 into the
rolling assay (see Fig. 2B), although rolling speeds were
essentially unchanged. These results are in contrast to the finding of
Campbell et al. (10), who in their assay with PNAd-coated
plates found increased rolling speeds of lymphocytes in the presence of
SDF-1. Moreover, reduced rolling speeds of lymphocytes on
endothelial cells upon addition of IP10 and MIP-1ß has been shown
(30). Slower rolling could allow more efficient sampling
of locally produced chemokines and lead to the firm attachment of the
cells at lower concentrations of chemokines. The combined effects of
multiple chemokines, some inducing slower rolling while others
triggering tight adhesion, during endothelial transmigration of
leukocytes could be physiologically advantageous and lead to more
effective regulation of lymphocyte extravasation. Importantly,
desensitization to some chemokines could also be a major regulatory
determinant in lymphocyte migration and deserves to be a focus of
further studies.
In conclusion, our study demonstrates the striking effect of soluble
SDF-1 on the binding of T cells to a monolayer of endothelial
cells under flow conditions. We show that within 20 s upon contact
with soluble SDF-1, >90% of the rolling lymphocytes firmly
attached to the endothelium. Peak binding was seen at 2–3 min, which
was followed by either permanent or transient adhesion and continued
rolling on the endothelium. The cells that deattached exhibited an
increased capacity to roll on the endothelium and were still capable of
firmly binding to the endothelium following the addition of PMA to the
system. The same adhesion molecules that supported the rolling before
the addition of the chemokine were also supporting the rolling of the
desensitized lymphocytes. The firm adhesion in response to SDF-1 was
due to the effect of the chemokine on the lymphocytes, since it could
be blocked by pretreating the lymphocytes with PTX. These results
further enhance our understanding of the multistep process of
lymphocyte homing and emphasize the importance of homotypic
desensitization to activating chemokines in this process.
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Mark A. Jutila, Veterinary Molecular Biology, Montana State University, P.O. Box 173610 MSU, Bozeman, MT 59717-3610.
3 Abbreviations used in this paper: SDF-1, stromal cell-derived factor-1; PNAd, peripheral node addressin; IP10, IFN- induced protein-10; Mig, monokine induced by IFN-; PTX, pertussis toxin.
Received for publication November 29, 1999. Accepted for publication February 28, 2000.
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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4 ß7 and LFA-1 in lymphocyte homing to Peyer’s patch-HEV in situ: the multistep model confirmed and refined. Immunity 3:99.[Medline]
4 ß7-mediated adhesion of lymphocytes to mucosal addressin cell adhesion molecule-1 (MAdCAM-1) under flow. J. Immunol. 161:952./ T cells. J. Immunol. 153:3917.[Abstract]
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