An optimized live-cell microscopy assay reveals human T-cells primarily respond chemokinetically to chemokines, in contrast to the chemotactic responses of human dendritic cells — ASN Events
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An optimized live-cell microscopy assay reveals human T-cells primarily respond chemokinetically to chemokines, in contrast to the chemotactic responses of human dendritic cells (#310)

Evert J. Loef 1 2 , Rod Dunbar 1 2 , Nigel P. Birch 1 3
  1. School of Biological Science, University of Auckland, Auckland, New Zealand
  2. Maurice Wilkins Centre for Molecular Biodiscovery, University of Auckland, Auckland, New Zealand
  3. Centre for Brain Research and Brain Research New Zealand; Rangahau Roro Aotearoa, University of Auckland, Auckland, New Zealand

Immune function depends on the ability of immune cells to respond to migratory signals. While migration induced by chemokines is often assumed to be directional (chemotaxis), end-point migration assays commonly used in the literature are confounded by the detection of increased cell migration that lacks directionality (chemokinesis).

To distinguish between chemotaxis and chemokinesis, we developed a modified live-cell video microscopy assay to monitor cell migration under agarose/agar. We placed chemokines in two separate wells in medium containing agar to generate different gradients of soluble chemokines in the surrounding agar, and simultaneously live-imaged how these competing gradients influenced the migration of human immune cells, including mixtures of differentially-labelled cells. This modified "under-agarose" assay allowed careful comparison of migratory responses to different types of chemokine signal, including comparing responses to chemokine gradients versus steady state concentrations.

The gradients generated in our assay system, imaged with a fluorescent marker, lasted several hours. Over that time period, CCR7+ monocyte-derived human dendritic cells (moDCs) migrated chemotactically in the direction of a CCL19 gradient. In contrast, under the same gradient of CCL19, CCR7+ T-cells exhibited increased exploratory chemokinesis, resembling a random walk, but only showed a minor directional bias toward CCL19. Similarly, activated T-cells that express CXCR4 showed increased exploratory chemokinesis in response to CXCL12, but displayed no chemotaxis in the direction of a gradient of CXCL12.

These T-cell specific motility patterns are consistent with the concept that T-cells use strategies to optimize their response between environmental cues, such as chemokines, and exploration of new information, enabling efficient scanning for antigen presenting cells (APCs) in lymphoid tissue, and APCs and target cells in peripheral tissues. However, the minor directional component of CCR7-driven motility in human T-cells might be important in driving their initial migration into lymphoid tissues rich in CCL19 and CCL21.

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