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L-selectin-mediated leukocyte adhesion in vivo: microvillous distribution determines tethering efficiency, but not rolling velocity.

Stein JV, Cheng G, Stockton BM, Fors BP, Butcher EC, von Andrian UH - J. Exp. Med. (1999)

Bottom Line: In the narrow venules, tethering of cells with cell body expression may have been aided by forced margination through collision with erythrocytes.L-selectin transfected cells rolled 10-fold faster than E-selectin transfectants.Interestingly, rolling velocity histograms of cell lines expressing equivalent copy numbers of the same ectodomain were always similar, irrespective of the topographic distribution.

View Article: PubMed Central - PubMed

Affiliation: Center for Blood Research and the Department of Pathology, Harvard Medical School, Boston, Massachusetts 02115, USA.

ABSTRACT
Adhesion receptors that are known to initiate contact (tethering) between blood-borne leukocytes and their endothelial counterreceptors are frequently concentrated on the microvilli of leukocytes. Other adhesion molecules are displayed either randomly or preferentially on the planar cell body. To determine whether ultrastructural distribution plays a role during tethering in vivo, we used pre-B cell transfectants expressing L- or E-selectin ectodomains linked to transmembrane/intracellular domains that mediated different surface distribution patterns. We analyzed the frequency and velocity of transfectant rolling in high endothelial venules of peripheral lymph nodes using an intravital microscopy model. Ectodomains on microvilli conferred a higher efficiency at initiating rolling than random distribution which, in turn, was more efficient than preferential expression on the cell body. The role of microvillous presentation was less accentuated in venules below 20 micrometers in diameter than in larger venules. In the narrow venules, tethering of cells with cell body expression may have been aided by forced margination through collision with erythrocytes. L-selectin transfected cells rolled 10-fold faster than E-selectin transfectants. Interestingly, rolling velocity histograms of cell lines expressing equivalent copy numbers of the same ectodomain were always similar, irrespective of the topographic distribution. Our data indicate that the distribution of adhesion receptors has a dramatic impact on contact initiation between leukocytes and endothelial cells, but does not play a role once rolling has been established.

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Rolling fractions of  L1-2 cells expressing the E-selectin ED in PLN venules. Rolling  fractions in PLN venules of transfectants expressing E-selectin (random distribution) and E/L chimera (on microvilli) are presented  as in Fig. 2. (A) Rolling fractions  of E/L and wild-type E-selectin  transfectants in paired venules.  (B) Relative rolling fraction determined by normalizing the  rolling fraction of E-selectin  transfectants to that of E/L transfectants in each venule; data are  shown as mean ± SEM of rolling  fractions in 18 venules from three  independent experiments.
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Figure 4: Rolling fractions of L1-2 cells expressing the E-selectin ED in PLN venules. Rolling fractions in PLN venules of transfectants expressing E-selectin (random distribution) and E/L chimera (on microvilli) are presented as in Fig. 2. (A) Rolling fractions of E/L and wild-type E-selectin transfectants in paired venules. (B) Relative rolling fraction determined by normalizing the rolling fraction of E-selectin transfectants to that of E/L transfectants in each venule; data are shown as mean ± SEM of rolling fractions in 18 venules from three independent experiments.

Mentions: An earlier study has reported that E-selectin/IgG chimeric molecules bind to PNAd in HEV in frozen sections of murine PLN and human tonsils (22), and E-selectin– transfected cells were shown to bind to immobilized PNAd (23). Thus, we tested whether L1-2 cells expressing human E-selectin could interact with subiliac LN venules. Indeed, cells expressing E-selectin EDs tethered and rolled in PLN HEV similar to L-selectin transfectants, i.e., rolling fractions were highest in order IV and V venules, and decreased in lower order venules (Fig. 4 A).


L-selectin-mediated leukocyte adhesion in vivo: microvillous distribution determines tethering efficiency, but not rolling velocity.

Stein JV, Cheng G, Stockton BM, Fors BP, Butcher EC, von Andrian UH - J. Exp. Med. (1999)

Rolling fractions of  L1-2 cells expressing the E-selectin ED in PLN venules. Rolling  fractions in PLN venules of transfectants expressing E-selectin (random distribution) and E/L chimera (on microvilli) are presented  as in Fig. 2. (A) Rolling fractions  of E/L and wild-type E-selectin  transfectants in paired venules.  (B) Relative rolling fraction determined by normalizing the  rolling fraction of E-selectin  transfectants to that of E/L transfectants in each venule; data are  shown as mean ± SEM of rolling  fractions in 18 venules from three  independent experiments.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC1887701&req=5

Figure 4: Rolling fractions of L1-2 cells expressing the E-selectin ED in PLN venules. Rolling fractions in PLN venules of transfectants expressing E-selectin (random distribution) and E/L chimera (on microvilli) are presented as in Fig. 2. (A) Rolling fractions of E/L and wild-type E-selectin transfectants in paired venules. (B) Relative rolling fraction determined by normalizing the rolling fraction of E-selectin transfectants to that of E/L transfectants in each venule; data are shown as mean ± SEM of rolling fractions in 18 venules from three independent experiments.
Mentions: An earlier study has reported that E-selectin/IgG chimeric molecules bind to PNAd in HEV in frozen sections of murine PLN and human tonsils (22), and E-selectin– transfected cells were shown to bind to immobilized PNAd (23). Thus, we tested whether L1-2 cells expressing human E-selectin could interact with subiliac LN venules. Indeed, cells expressing E-selectin EDs tethered and rolled in PLN HEV similar to L-selectin transfectants, i.e., rolling fractions were highest in order IV and V venules, and decreased in lower order venules (Fig. 4 A).

Bottom Line: In the narrow venules, tethering of cells with cell body expression may have been aided by forced margination through collision with erythrocytes.L-selectin transfected cells rolled 10-fold faster than E-selectin transfectants.Interestingly, rolling velocity histograms of cell lines expressing equivalent copy numbers of the same ectodomain were always similar, irrespective of the topographic distribution.

View Article: PubMed Central - PubMed

Affiliation: Center for Blood Research and the Department of Pathology, Harvard Medical School, Boston, Massachusetts 02115, USA.

ABSTRACT
Adhesion receptors that are known to initiate contact (tethering) between blood-borne leukocytes and their endothelial counterreceptors are frequently concentrated on the microvilli of leukocytes. Other adhesion molecules are displayed either randomly or preferentially on the planar cell body. To determine whether ultrastructural distribution plays a role during tethering in vivo, we used pre-B cell transfectants expressing L- or E-selectin ectodomains linked to transmembrane/intracellular domains that mediated different surface distribution patterns. We analyzed the frequency and velocity of transfectant rolling in high endothelial venules of peripheral lymph nodes using an intravital microscopy model. Ectodomains on microvilli conferred a higher efficiency at initiating rolling than random distribution which, in turn, was more efficient than preferential expression on the cell body. The role of microvillous presentation was less accentuated in venules below 20 micrometers in diameter than in larger venules. In the narrow venules, tethering of cells with cell body expression may have been aided by forced margination through collision with erythrocytes. L-selectin transfected cells rolled 10-fold faster than E-selectin transfectants. Interestingly, rolling velocity histograms of cell lines expressing equivalent copy numbers of the same ectodomain were always similar, irrespective of the topographic distribution. Our data indicate that the distribution of adhesion receptors has a dramatic impact on contact initiation between leukocytes and endothelial cells, but does not play a role once rolling has been established.

Show MeSH
Related in: MedlinePlus