Lymphocyte Migration in Lymphocyte Function-associated Antigen (LFA)-1–deficient Mice

Using lymphocyte function-associated antigen (LFA)-1(−/−) mice, we have examined the role of LFA-1 and other integrins in the recirculation of lymphocytes. LFA-1 has a key role in migration to peripheral lymph nodes (pLNs), and influences migration into other LNs. Second, the α4 integrins, α4β7 and α4β1, have a hitherto unrecognized ability to compensate for the lack of LFA-1 in migration to pLNs. These findings are confirmed using normal mice and blocking LFA-1 and α4 monoclonal antibodies. Unexpectedly, vascular cell adhesion molecule (VCAM)-1, which is essential in inflammatory responses, serves as the ligand for the α4 integrins on pLN high endothelial venules. VCAM-1 also participates in trafficking into mesenteric LNs and Peyer's patch nodes where mucosal addressin cell adhesion molecule 1 (MAdCAM-1), the α4β7-specific ligand, dominates. Both α4β1, interacting with ligand VCAM-1, and also LFA-1 participate in substantial lymphocyte recirculation through bone marrow. These observations suggest that organ-specific adhesion receptor usage in mature lymphocyte recirculation is not as rigidly adhered to as previously considered, and that the same basic sets of adhesion receptors are used in both lymphocyte homing and inflammatory responses.