Invasion of collagen gels by mouse lymphoid cells

Small mouse lymphocytes from lymph nodes rapidly invaded three-dimensional collagen gels (in the absence of any added chemical attractant). In short-term assays (2-8 hr) this property was restricted to 20-25% of the cell population. Invasion was an active process involving cell locomotion. Time-lapse cinematography revealed that movement was erratic with frequent changes in cell speed. Tracks of cell paths within collagen gels demonstrated that lymphocytes made narrow angles of turn and thus showed a 'persistent random-walk' similar to other cell types moving on plane substrata. Analysis of lymphocyte movement within aligned collagen gels demonstrated that locomotion was biased in the axis of fibre alignment, i.e. lymphocytes showed contact guidance. Separated B lymphocytes invaded collagen gels at a slower rate than unseparated lymph node cells, as also did T cells purified by filtration through nylon wool columns. This latter anomaly implied that nylon wool filtration selectively depleted cells with invasive characteristics from a heterogeneous lymphocyte population. A comparison of Peyer's patch and lymph node lymphocytes showed that both populations invaded at the same rate but the latter cell type did this in greater numbers. This difference may reflect the different proportions of B and T lymphocytes in the two tissues. Lymphocytes from oxazolone-stimulated lymph nodes showed greatly increased movement into collagen matrices compared to unstimulated control lymph node lymphocytes. This increase was demonstrated to be a property of the blast cell population by separating the cells on Percoll gradients into lymphoblast-enriched and -depleted populations.