Locomotion of human T lymphocytes in 3-D collagen lattices in vitro -adhesion requirements and redistribution of β1 integrins

The mechanism of T cell migration within the tissues may involve the coordinated adhesion and deadhesion ofl (VLA) integrins to ligands of the extracellular matrix. Using a highly sensitive T cell migration approach in combination with computer-assisted cell tracking and quantitative data analysis, the locomotion of non-activated as well as Con A-stimulated human CD4⁺ and CD8⁺ lymphocytes within 3-D collagen lattices could not be inhibited by blocking anti-61 integrin mAbs 4B4, Lia 1/2, 13, DE9, and P4CIO, either alone or in combination. In contrast, activating anti-l mAb TS2/16 led to a pronounced but transient reduction in migration (1 to 3 h) which was completely antagonized by mAb 4B4 or a combination of blocking anti-l mAbs. On locomoting T cells, an increased number of physical contacts to the collagen fibrils was related with the development of an uropod at the rear side of the cell, as detected by laserscanning reflection microscopy. During locomotion, l integrins prominently redistributed towards the uropod at attachment sites to the matrix, whereas, at the leading edge, focal adhesion contacts to collagen fibrils containing patches of phosphotyrosine residues and focal adhesion kinase (pp125^FAK) snowed no clustering of B1 integrins. This polar redistribution pattern of β1 integrins as well as the differential usage of individual fibrils in the process of translocation were not affected by blocking anti-l mAbs, as deteceted by three-color confocal time series analysis of migrating cells. In conclusion, adhesion and focal clustering of l integrins may not be a prerequisite for T cell locomotion within 3-D collagen lattices, however, activatory signals via βl integrins can result in adhesiondependent stopping signals in previously locomoting T cells.