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Multistep navigation and the combinatorial control of leukocyte chemotaxis.

Foxman EF, Campbell JJ, Butcher EC - J. Cell Biol. (1997)

Bottom Line: Furthermore, cells can chemotax effectively to a secondary distant agonist after migrating up a primary gradient into a saturating, nonorienting concentration of an initial attractant.Together, these observations suggest the potential for cells' step-by-step navigation from one gradient to another in complex chemoattractant fields.We propose a multistep model of chemoattractant-directed migration, which requires that leukocytes display multiple chemoattractant receptors for successful homing and provides for combinatorial determination of microenvironmental localization.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Immunology and Vascular Biology, Department of Pathology, and the Digestive Disease Center, Department of Medicine, Stanford University Medical School, Stanford, California 94305-5324, USA.

ABSTRACT
Cells migrating within tissues may encounter multiple chemoattractant signals in complex spatial and temporal patterns. To understand leukocyte navigation in such settings, we have explored the migratory behavior of neutrophils in model scenarios where they are presented with two chemoattractant sources in various configurations. We show that, over a wide range of conditions, neutrophils can migrate "down" a local chemoattractant gradient in response to a distant gradient of a different chemoattractant. Furthermore, cells can chemotax effectively to a secondary distant agonist after migrating up a primary gradient into a saturating, nonorienting concentration of an initial attractant. Together, these observations suggest the potential for cells' step-by-step navigation from one gradient to another in complex chemoattractant fields. The importance of such sequential navigation is confirmed here in a model system in which neutrophil homing to a defined domain (a) requires serial responses to agonists presented in a defined spatial array, and (b) is a function of both the agonist combination and the sequence in which gradients are encountered. We propose a multistep model of chemoattractant-directed migration, which requires that leukocytes display multiple chemoattractant receptors for successful homing and provides for combinatorial determination of microenvironmental localization.

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Neutrophil navigation  targeted by sequential migration  to chemoattractants in a defined  spatial array. (a) Diagram illustrating the position of the two agonist wells relative to the cell  well, and the outline of the target zone used to quantitate the  number of cells migrating sequentially to both agonists (see  c). (b) Photographs of fixed,  stained cells that have been allowed to migrate for 3 h in the  presence or absence of a central  agonist (right side of photos)  and/or side agonist (left side of  photos). The approximate position of the target zone is indicated in each image (for quantitative analyses, target zones  were precisely positioned by a  template). Successfully homed  cells have been accentuated for  illustrative purposes by enhancing the contrast in the target region. The amounts of IL-8,  LTB4, and fMLP in the agonist  wells were 1 pmol, 1 pmol, and  0.5 pmol, respectively. (c) Graph  indicating the number of cells  migrating into the defined target  zone in presence of various agonist combinations. The mean  number of cells entering the target zone is indicated. Error bars  show the range for two replicate  determinations from a representative experiment. Asterisks indicate that the mean number of  cells in the target region was  <15. (d) Turning behavior of  cells migrating to two agonists in  sequence. Dots indicate the center of the leading edge of migrating cells at various times for  cells responding to a central IL-8  source and side LTB4 source  (top) or a central IL-8 source  and side fMLP source (bottom).
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Figure 7: Neutrophil navigation targeted by sequential migration to chemoattractants in a defined spatial array. (a) Diagram illustrating the position of the two agonist wells relative to the cell well, and the outline of the target zone used to quantitate the number of cells migrating sequentially to both agonists (see c). (b) Photographs of fixed, stained cells that have been allowed to migrate for 3 h in the presence or absence of a central agonist (right side of photos) and/or side agonist (left side of photos). The approximate position of the target zone is indicated in each image (for quantitative analyses, target zones were precisely positioned by a template). Successfully homed cells have been accentuated for illustrative purposes by enhancing the contrast in the target region. The amounts of IL-8, LTB4, and fMLP in the agonist wells were 1 pmol, 1 pmol, and 0.5 pmol, respectively. (c) Graph indicating the number of cells migrating into the defined target zone in presence of various agonist combinations. The mean number of cells entering the target zone is indicated. Error bars show the range for two replicate determinations from a representative experiment. Asterisks indicate that the mean number of cells in the target region was <15. (d) Turning behavior of cells migrating to two agonists in sequence. Dots indicate the center of the leading edge of migrating cells at various times for cells responding to a central IL-8 source and side LTB4 source (top) or a central IL-8 source and side fMLP source (bottom).

Mentions: To model this type of scenario, we assessed the behavior of cells responding to attractants presented in two wells, one “central” well located 2.2 mm from the cell well (as in the previous assays), and the second “side” well positioned at a 90° angle, 2.2 mm from the central well and 4.5 mm from the cell well (Fig. 7 a). We defined an arbitrary target zone, as illustrated in the figure, and asked whether neutrophils could be attracted to this target zone by chemoattractants presented in various combinations in the primary (central) and/or the more distant, secondary attractant wells. All agonists were used at optimal chemoattractant concentrations (defined for the proximal well, Fig. 7, legend). As illustrated in Fig. 7 b, and shown quantitatively in Fig. 7 c, cells migrated well in response to IL-8 in the central well, but could not enter the target zone in significant numbers. When IL-8, LTB4, or both were presented in the side well only, cells were able to migrate a short distance directly towards the side well, but did not enter the target zone. When IL-8 was presented in both the central and side wells, cells migrated only towards the closer central well; this was not unexpected, as locally this would be seen as “upgradient” in spite of the additional, more distant source of the same agonist. Finally, when IL-8 was presented in the central well and LTB4 was presented in the side well, neutrophils were able to home to the target zone in large numbers (Fig. 7, b and c).


Multistep navigation and the combinatorial control of leukocyte chemotaxis.

Foxman EF, Campbell JJ, Butcher EC - J. Cell Biol. (1997)

Neutrophil navigation  targeted by sequential migration  to chemoattractants in a defined  spatial array. (a) Diagram illustrating the position of the two agonist wells relative to the cell  well, and the outline of the target zone used to quantitate the  number of cells migrating sequentially to both agonists (see  c). (b) Photographs of fixed,  stained cells that have been allowed to migrate for 3 h in the  presence or absence of a central  agonist (right side of photos)  and/or side agonist (left side of  photos). The approximate position of the target zone is indicated in each image (for quantitative analyses, target zones  were precisely positioned by a  template). Successfully homed  cells have been accentuated for  illustrative purposes by enhancing the contrast in the target region. The amounts of IL-8,  LTB4, and fMLP in the agonist  wells were 1 pmol, 1 pmol, and  0.5 pmol, respectively. (c) Graph  indicating the number of cells  migrating into the defined target  zone in presence of various agonist combinations. The mean  number of cells entering the target zone is indicated. Error bars  show the range for two replicate  determinations from a representative experiment. Asterisks indicate that the mean number of  cells in the target region was  <15. (d) Turning behavior of  cells migrating to two agonists in  sequence. Dots indicate the center of the leading edge of migrating cells at various times for  cells responding to a central IL-8  source and side LTB4 source  (top) or a central IL-8 source  and side fMLP source (bottom).
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Figure 7: Neutrophil navigation targeted by sequential migration to chemoattractants in a defined spatial array. (a) Diagram illustrating the position of the two agonist wells relative to the cell well, and the outline of the target zone used to quantitate the number of cells migrating sequentially to both agonists (see c). (b) Photographs of fixed, stained cells that have been allowed to migrate for 3 h in the presence or absence of a central agonist (right side of photos) and/or side agonist (left side of photos). The approximate position of the target zone is indicated in each image (for quantitative analyses, target zones were precisely positioned by a template). Successfully homed cells have been accentuated for illustrative purposes by enhancing the contrast in the target region. The amounts of IL-8, LTB4, and fMLP in the agonist wells were 1 pmol, 1 pmol, and 0.5 pmol, respectively. (c) Graph indicating the number of cells migrating into the defined target zone in presence of various agonist combinations. The mean number of cells entering the target zone is indicated. Error bars show the range for two replicate determinations from a representative experiment. Asterisks indicate that the mean number of cells in the target region was <15. (d) Turning behavior of cells migrating to two agonists in sequence. Dots indicate the center of the leading edge of migrating cells at various times for cells responding to a central IL-8 source and side LTB4 source (top) or a central IL-8 source and side fMLP source (bottom).
Mentions: To model this type of scenario, we assessed the behavior of cells responding to attractants presented in two wells, one “central” well located 2.2 mm from the cell well (as in the previous assays), and the second “side” well positioned at a 90° angle, 2.2 mm from the central well and 4.5 mm from the cell well (Fig. 7 a). We defined an arbitrary target zone, as illustrated in the figure, and asked whether neutrophils could be attracted to this target zone by chemoattractants presented in various combinations in the primary (central) and/or the more distant, secondary attractant wells. All agonists were used at optimal chemoattractant concentrations (defined for the proximal well, Fig. 7, legend). As illustrated in Fig. 7 b, and shown quantitatively in Fig. 7 c, cells migrated well in response to IL-8 in the central well, but could not enter the target zone in significant numbers. When IL-8, LTB4, or both were presented in the side well only, cells were able to migrate a short distance directly towards the side well, but did not enter the target zone. When IL-8 was presented in both the central and side wells, cells migrated only towards the closer central well; this was not unexpected, as locally this would be seen as “upgradient” in spite of the additional, more distant source of the same agonist. Finally, when IL-8 was presented in the central well and LTB4 was presented in the side well, neutrophils were able to home to the target zone in large numbers (Fig. 7, b and c).

Bottom Line: Furthermore, cells can chemotax effectively to a secondary distant agonist after migrating up a primary gradient into a saturating, nonorienting concentration of an initial attractant.Together, these observations suggest the potential for cells' step-by-step navigation from one gradient to another in complex chemoattractant fields.We propose a multistep model of chemoattractant-directed migration, which requires that leukocytes display multiple chemoattractant receptors for successful homing and provides for combinatorial determination of microenvironmental localization.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Immunology and Vascular Biology, Department of Pathology, and the Digestive Disease Center, Department of Medicine, Stanford University Medical School, Stanford, California 94305-5324, USA.

ABSTRACT
Cells migrating within tissues may encounter multiple chemoattractant signals in complex spatial and temporal patterns. To understand leukocyte navigation in such settings, we have explored the migratory behavior of neutrophils in model scenarios where they are presented with two chemoattractant sources in various configurations. We show that, over a wide range of conditions, neutrophils can migrate "down" a local chemoattractant gradient in response to a distant gradient of a different chemoattractant. Furthermore, cells can chemotax effectively to a secondary distant agonist after migrating up a primary gradient into a saturating, nonorienting concentration of an initial attractant. Together, these observations suggest the potential for cells' step-by-step navigation from one gradient to another in complex chemoattractant fields. The importance of such sequential navigation is confirmed here in a model system in which neutrophil homing to a defined domain (a) requires serial responses to agonists presented in a defined spatial array, and (b) is a function of both the agonist combination and the sequence in which gradients are encountered. We propose a multistep model of chemoattractant-directed migration, which requires that leukocytes display multiple chemoattractant receptors for successful homing and provides for combinatorial determination of microenvironmental localization.

Show MeSH
Related in: MedlinePlus