Rapid Acquisition of Tissue-specific Homing Phenotypes by CD4<b>+</b> T Cells Activated in Cutaneous or Mucosal Lymphoid Tissues

Effector and memory T cells can be subdivided based on their ability to traffic through peripheral tissues such as inflamed skin and intestinal lamina propria, a property controlled by expression of ‘tissue-specific’ adhesion and chemoattractant receptors. However, little is known about the development of these selectively homing T cell subsets, and it is unclear whether activation in cutaneous versus intestinal lymphoid organs directly results in effector/memory T cells that differentially express adhesion and chemoattracant receptors targeting them to the corresponding nonlymphoid site. We define two murine CD4+ effector/memory T cell subsets that preferentially localize in cutaneous or intestinal lymphoid organs by their reciprocal expression of the adhesion molecules P-selectin ligand (P-lig) and α4β7, respectively. We show that within 2 d of systemic immunization CD4+ T cells activated in cutaneous lymph nodes upregulate P-lig, and downregulate α4β7, while those responding to antigen in intestinal lymph nodes selectively express high levels of α4β7 and acquire responsiveness to the intestinal chemokine thymus-expressed chemokine (TECK). Thus, during an immune response, local m