FIGURE 1

Kruppel-like factor 2 (KLF2) controls T-lymphocyte trafficking. The transcription factor KLF2 controls key molecules (starred) that are involved in T-lymphocyte trafficking. Mature T cells in the thymus require the sphingosine 1 phosphate receptor 1 (S1P₁) for egress into circulation. Once circulating, T cells require L-selectin (CD62L) for entry into lymph nodes through high endothelial vessels. Egress from the lymph node into lymphatic vessels again requires S1P₁. As KLF2 controls these 'keys' to the front and back door on the lymph node, when naïve T cells express KLF2 (and subsequently S1P₁ and CD62L) they circulate through secondary lymphoid tissue (red arrows). When T cells are activated, they downregulate KLF2, causing a loss of S1P₁ and CD62L, and express chemokine receptors. This results in thymic retention (if the T cell is in the thymus) or movement from circulation to tissues (if the T cell is in the periphery) (shaded blue).