Distinct roles for LFA-1 affinity regulation during T-cell adhesion, diapedesis, and interstitial migration in lymph nodes

Abstract

During the course of homing to lymph nodes (LNs), T cells undergo a multistep adhesion cascade that culminates in a lymphocyte function-associated antigen 1 (LFA-1)-dependent firm adhesion to the luminal surface of high endothelial venules (HEVs). The importance of LFA-1 affinity regulation in supporting T-cell arrest on HEVs has been well established, however, its importance in the postadhesion phase, which involves intraluminal crawling and diapedesis to the extravascular space, remains elusive. Here we have shown that LFA-1 affinity needs to be appropriately regulated to support these essential steps in the homing cascade. Genetically engineered T cells that were unable to properly down-regulate LFA-1 affinity underwent enhanced, chemokine-independent arrest in HEVs but showed perturbed intravascular crawling to transmigration sites and compromised diapedesis across HEVs. By contrast, the extravascular migration of T cells was insensitive to the affinity-enhancing LFA-1 mutation. These results highlight the requirement for balanced LFA-1 affinity regulation in intravascular and transvascular, but not extravascular, T-cell migration in LNs. (Blood. 2010;115:1572-1581) IntroductionThe constant recirculation of naive T cells through secondary lymphoid organs is critical for immune surveillance. 1 A central event in this process is homing of T cells to lymph nodes (LNs) via high endothelial venules (HEVs). A current model of the homing cascade includes a sequence of at least 4 distinct steps 2-5 : (1) recruitment of circulating T cells to the luminal HEV surface, involving a rolling interaction and its subsequent conversion to firm adhesion upon chemokine activation; (2) intravascular migration of luminally adherent T cells that allows the translocation from the initial attachment site to a suitable exit site; (3) transendothelial diapedesis across HEVs; and (4) random migration of T cells within the extravascular compartment in LN parenchyma. Considerable information is available on the molecular and cellular mechanisms involved in the first and last step in this homing cascade; however, little is known about the rules that control the access of luminally adherent cells to the LN parenchyma.Integrin lymphocyte function-associated antigen 1 (LFA-1; ␣ L ␤ 2 ) is the predominant cell adhesion molecule present on T cells. 6-8 LFA-1 is an ␣/␤ heterodimeric transmembrane membrane protein that contains the ligand binding inserted (I) domain at the most distal part of the extracellular portion. 9 LFA-1 undergoes dynamic and regulated conformational changes in response to internal cues (eg, the intracellular signaling elicited by chemokine and T-cell receptors) as well as in response to external cues (eg, ligand densities and shear stress). [10][11][12] A series of in vitro investigations propose a model that explains how these sequential engagements of internal and external cues regulate LFA-1 conformations in T-cell interactions with intercellular adhesion molecule-1 (ICAM-1), the major LFA-1 ligand on endothelial cell...

Actin stabilizer TAGLN2 potentiates adoptive T cell therapy by boosting the inside-out costimulation via lymphocyte function-associated antigen-1

“…34 It has been shown that genetically engineered T cells with affinity-enhancing LFA-1 mutation show perturbed intravascular crawling to transmigration sites, thereby compromising diapedesis across the blood vessels. 35 In our case, however, overexpression of TAGLN2 did not affect the migration of OTI CD8 + T cells into the tumor sites, suggesting that LFA-1 avidity regulation does not influence T-cell diapedesis across the tumor blood vessels. Moreover, we found that tumor non-specific polyclonal TG2P-CD8 + T cells have little effect on tumor suppression (data not shown), suggesting that the TAGLN2–actin–LFA-1 axis can be effective when T cells are activated via TCRs or CARs.…”

A New Leukocyte Hyperadhesion Syndrome of Delayed Cord Separation, Skin Infection, and Nephrosis

“…Whereas the exact mechanism causing the hyperadhesiveness of the integrins is not known, the symptoms bear resemblance to mice expressing constitutively active LFA-1 in which excessive adhesion prevents leukocytes from entering injured tissues and, when tested in vitro, causes increased adhesion and stalled migration. [15][16] Insight into the mechanisms of glucocorticoid action might also help to explain the diminished recurrence of skin infections.…”

Distinct Binding Affinities of Mac-1 and LFA-1 in Neutrophil Activation

“…LFA-1 also supports monocyte firm adhesion and crawling in quiescent condition, whereas Mac-1 is responsible for TNF-a-stimulated monocyte crawling (16). Multiple functional states of LFA-1 with different affinities are required for lymphocyte rolling, adhesion, and crawling because no Mac-1 molecules are presented onto lymphocyte surface (17)(18)(19)(20). These observations bring up a question why the two structurally similar b 2 integrins behave distinctly in leukocyte recruitment and what the underlying mechanisms are.…”

“…Although a body of evidences has been found to focus on the functional differences between Mac-1 and LFA-1 using in vivo, ex vivo, and in vitro measurements (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23), it is still hard to provide a mechanistic insight. One way to elucidate the underlying mechanisms is to quantify the binding kinetics because it determines the on-and off-rates and binding affinity of interacting molecules.…”