Phenotype, and migration properties of three major subsets of tissue homing T cells in sheep

T cells show a bias in their migration pathways: some T cells preferentially migrate to peripheral lymph nodes (LN), some to mucosal tissues, and some to peripheral tissues such as skin. These recirculation pathways were examined in sheep by collecting lymph draining into and out of peripheral and intestinal LN, and using fluorescent dyes to trace the recirculation of the lymph cells. Monoclonal antibodies (mAb) to α4, β1, and β7 integrins, and L-selectin, were used to define three major populations of recirculating T cells. Naive-type T cells (L-selectin⁺, α4β1(lo)β7(lo)) migrated preferentially through peripheral LN. Two memory populations could be defined: α4β1(hi)β7^- and α4β7(hi)β1(lo). α4β1(hi)β7^- T cells were present in lymph draining from the skin. T cells migrating preferentially through intestinal LN were α4β7(hi)β1(lo). Consistent with this migration pattern, the endothelial receptor for α4β7, mucosal addressin cell adhesion molecule-1 (MAdCAM-1) was detected on high endothelial venules within intestinal LN and Peyer's patches, but only weakly on high endothelial venules within peripheral LN. Thus, there are at least three easily definable subsets of T cells, based on integrin expression, which show distinct migration preferences.