Fig. 1. The multistep model of T-cell migration. T cells migrate from the blood, across the vascular endothelium into infected tissue or into lymph node (LN). The receptors involved in stages 1-6 are indicated in tabular form. The process of crossing the endothelial barrier into infected tissue or LN is similar. However, in LN, T cells crawl within a network of fibroblastic reticular cell-coated cables and, in infected tissues, they migrate along matrices composed chiefly of collagen fibrils. Abbreviations: CCL, chemokine ligand; CCR, chemokine receptor; PBM, perivascular basement membrane;?, lack of information.