Haptotactic activity of fibronectin on lymphocyte migration in vitro

In addition to mediating cell adhesion, fibronectin (FN) also affects the migration of different cell types. However, the role of FN in lymphocyte migration is unclear. In this study, we examined the effects of FN on the in vitro migration of lymphocytes. Using the checkerboard analysis in a blind-well microchemotaxis assay, soluble FN was determined to have neither a chemotactic nor chemokinetic effect on spleen or thymus lymphocytes. However, when the nitrocellulose filter was coated unidirectionally with FN, the migration of both spleen and thymus lymphocytes into the filter was enhanced, indicating that FN is haptotactic for lymphocytes. When the filter was coated bidirectionally, no enhancement in migration was observed, indicating that FN is not haptokinetic for lymphocytes. When the FN cell-binding domain and the heparin-binding domain were tested, the cell-binding domain was haptotactic for both spleen and thymus lymphocytes, whereas the heparin-binding domain was only haptotactic for spleen lymphocytes. Because the heparin-binding domain can mediate strong adhesion of thymus lymphocytes, the lack of haptotactic activity is likely to be the result of excessive binding that prevents cell motility.