Developmental and antigen-driven switches in the trafficking receptors of FoxP3+ regulatory T cells (99.2)

Abstract

Abstract FoxP3+ regulatory T cells play important roles in immune regulation and tolerance. There is an increasing body of evidence that the migration ability of FoxP3+ T cells is important for their regulatory functions at effector tissue sites. We investigated the two different trafficking receptor switches of FoxP3+ T cells occurring in the thymus and secondary lymphoid tissues. The first trafficking receptor switch in the thymus is developmentally programmed: Precursors of FoxP3+ cells undergo the first trafficking receptor switch from CCR8/CCR9 to CXCR4 and then finally to CCR7, generating mostly homogeneous CD62L+CCR7+ FoxP3+ T cells. The recent thymic emigrant CD62L+CCR7+ FoxP3+ T cells are programmed to migrate to secondary lymphoid tissues. The CD62L+CCR7+ FoxP3+ T cells undergo the second switch in trafficking receptors in an antigen-dependent manner. This second switch involves down-regulation of CCR7 and CXCR4 but up-regulation of a number of memory/effector type homing receptors, resulting in generation of heterogeneous FoxP3+ T cell subsets expressing various combinations of trafficking receptors including CCR2, CCR4, CCR5, CCR6, CCR7, CCR8, CCR9 and CXCR5. FoxP3+ cells undergo the second switch to selected non-lymphoid tissue homing receptors at highly accelerated rates. This results in generation of FoxP3+ T cells with unconventionally efficient migratory capacity to major non-lymphoid tissues such as intestinal lamina propria and bone marrow. Importantly, this accelerated switch of FoxP3+ T cells is conserved in both men and mice. The two switches in homing receptors are though to be important for effective distribution and differentiation-dependent effector functions of FoxP3+ regulatory T cells.