Naïve T cells in the absence of CCL21 are round and exhibit mostly Brownian motion. (Courtesy of Darrell Irvine. Used with permission.)
Naïve T cells in the presence of sufficient CCL21 will polarize and migrate along a protein-coated surface. (Courtesy of Darrell Irvine. Used with permission.)
Reference: Stachowiak, A., et al. "Homeostatic Lymphoid Chemokines Synergize with Adhesion Ligands to Trigger T and B Lymphocyte Chemokinesis." J Immunol 177 (2006): 2340-2348.
Activated T cells are able to migrate through a 3-dimensional porous polymeric scaffold. T cells were stimulated with CCL21 and the polymer was coated with an adhesion protein. (Copyright © 2010 Wiley Periodicals, Inc., A Wiley Company. Reprinted with permission of John Wiley & Sons., Inc.)
Reference: Supporting video for Stachowiak, A. N., and D. J. Irvine. "Inverse opal hydrogel-collagen composite scaffolds as a supportive microenvironment for immune cell migration." J Biomed Mater Res 85A, no.3 (2008): 815-828.