Molecular Mechanisms of Lymphocyte Homing to Peripheral Lymph Nodes

Abstract

To characterize the adhesion cascade that directs lymphocyte homing to peripheral lymph nodes (PLNs), we investigated the molecular mechanisms of lymphocyte interactions with the microvasculature of subiliac lymph nodes. We found that endogenous white blood cells and adoptively transferred lymph node lymphocytes (LNCs) tethered and rolled in postcapillary high endothelial venules (HEVs) and to a lesser extent in collecting venules. Similarly, firm arrest occurred nearly exclusively in the paracortical HEVs. Endogenous polymorphonuclear (PMNs) and mononuclear leukocytes (MNLs) attached and rolled in HEVs at similar frequencies, but only MNLs arrested suggesting that the events downstream of primary rolling interactions critically determine the specificity of lymphocyte recruitment. Antibody inhibition studies revealed that L-selectin was responsible for attachment and rolling of LNCs, and that LFA-1 was essential for sticking. LFA-1–dependent arrest was also abolished by pertussis toxin, implicating a requirement for Gαi−-protein–linked signaling. α4 integrins, which play a critical role in lymphocyte homing to Peyer's Patches, made no significant contribution to attachment, rolling, or sticking in resting PLNs. Velocity analysis of interacting LNCs revealed no detectable contribution by LFA-1 to rolling. Taken together, our results suggest that lymphocyte– HEV interactions within PLNs are almost exclusively initiated by L-selectin followed by a G protein–coupled lymphocyte-specific activation event and activation-induced engagement of LFA-1. These events constitute a unique adhesion cascade that dictates the specificity of lymphocyte homing to PLNs.

Visualization and in situ analysis of leukocyte trafficking into the ankle joint in a systemic murine model of rheumatoid arthritis

“…The ankle was immobilized by gripping the malleoli in a custom-built vise (as indicated in Figure 1B) that was mounted on a glass plate. Blood was drawn from the retroorbital vein (to determine systemic leukocyte counts), and then rhodamine 6G (Molecular Probes, Eugene, OR) was injected intravenously at a dose of 3 mg/kg for the in vivo labeling of circulating leukocytes (9,16). The intraarticular tissue was accessed by transection of the Achilles tendon at the calcaneal insertion site (see Figure 1B).…”

“…In most IVM experiments included in this study, we used the fluorescent membrane-permeable DNA dye rhodamine 6G for in vivo staining of nucleated cells in the peripheral blood (9,16). Rhodamine 6G permeates leukocytes (and platelets) in minutes, does not interfere with leukocyte-vessel interactions, and its unbound portion is cleared rapidly from the circulation.…”

Reversibly locking a protein fold in an active conformation with a disulfide bond: Integrin αL I domains with high affinity and antagonist activityin vivo

“…Furthermore, it inhibited the transition of lymphocytes in lymphoid high endothelial venules from rolling adhesion to firm adhesion, but did not inhibit rolling adhesion. These steps are known to depend on ␣L␤2 and L-selectin, respectively (1,42), demonstrating the high specificity of the locked open I domain in vivo. Our results suggest that locked open I domains can be used to demonstrate the importance of specific molecular targets in disease processes and are therapeutic candidates.…”

Unique Subpopulations of CD56+ NK and NK-T Peripheral Blood Lymphocytes Identified by Chemokine Receptor Expression Repertoire

“…However, CD16 Ϫ NK cells express high levels of CCR7, and respond very well to CCR7 ligands. These cells also express very high levels of L-selectin, which is another molecule necessary for homing through high endothelial venule (31). This small subset of NK cells may thus have a role in the events that occur within secondary lymphoid organs, and it will be interesting to see whether these cells can be found in such organs in future studies.…”