title: Alpha4beta1-integrin activation is necessary for high-efficiency T-cell subset interactions with VCAM-1 under flow.
abstract: OBJECTIVE
  The purpose of this study was to examine the relationship between alpha4beta1-integrin state of activation on CD4+ T-cell subsets and their adhesive interaction to VCAM-1 under flow.
  
  
  METHODS
  Human CD4+ memory and naive T-cells were freshly isolated and effector-helper T-cell subsets. Th1 and Th2 cells, were differentiated in vitro from CD4+ naive T-cells. The expression of activation/ligand induced epitopes on beta1-integrins of each T-cell subset was assessed using mAb HUTS21 and mAb 15/7. T-cell subsets attachment and rolling on VCAM-1 was determined under defined flow conditions and the rates of attachment (ka), accumulation, and instantaneous rolling velocities were correlated to their beta1-integrin activation epitope expression.
  
  
  RESULTS
  A subset of memory T-cells constitutively express activation/ligand induced epitopes on beta1-integrins recognized by mAb HUTS21 and 15/7, whereas expression levels on naive T-cells is low or not detectable. Consistent with an activated phenotype, memory T-cells exhibit significantly higher rates of attachment and accumulation on VCAM-1 under flow as compared to naive T-cells. Interestingly, the expression of activation/ligand induced epitopes on beta1-integrins on Th2 cells and the ability of these cells to interact with VCAM-1 are comparable to memory T-cells. In contrast, Th1 cells did not interact as efficiently with VCAM-1, which correlated with lower expression of activation/ligand induced epitopes on these cells. VCAM-1 interactions are inhibited completely by pretreatment of the T-cells with blocking mAb to alpha4-integrins or beta1-integrins, indicating that alpha4beta1 is the predominant T-cell integrin involved.
  
  
  CONCLUSIONS
  Memory T-cells express constitutively active alpha4beta1-integrins, as compared to naive T-cells, which mediate high rates of initial attachment and sustained high-affinity adhesive interactions with VCAM-1 under flow conditions in vitro. Similarly, in vitro differentiated Th2 cells but not Th1 cells, which also express elevated levels of activated alpha4beta1-integrins, are capable of sustaining high-affinity adhesive interactions with VCAM-1. The differences observed in beta1-integrin activation on T-cell subsets may underlie selective recruitment patterns of T-cell subsets in vivo.
authors.affiliation: Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Y C
authors.initials: YC
authors.lastname: Lim
authors.forename: M W
authors.initials: MW
authors.lastname: Wakelin
authors.forename: L
authors.initials: L
authors.lastname: Henault
authors.forename: D J
authors.initials: DJ
authors.lastname: Goetz
authors.forename: T
authors.initials: T
authors.lastname: Yednock
authors.forename: C
authors.initials: C
authors.lastname: Cabañas
authors.forename: F
authors.initials: F
authors.lastname: Sánchez-Madrid
authors.forename: A H
authors.initials: AH
authors.lastname: Lichtman
authors.forename: F W
authors.initials: FW
authors.lastname: Luscinskas
mesh_terms: D002448:Cell Adhesion; D002634:Chemotaxis, Leukocyte / Q000502:physiology*; D005434:Flow Cytometry; D018056:Hemorheology; D006801:Humans; D007156:Immunologic Memory; D039041:Integrin alpha4beta1; D016023:Integrins / Q000502:physiology*; D017493:Leukocyte Common Antigens / Q000032:analysis; D008213:Lymphocyte Activation; D008222:Lymphokines / Q000096:biosynthesis; D016201:Receptors, Lymphocyte Homing / Q000502:physiology*; D018417:Th1 Cells / Q000166:cytology / Q000378:metabolism*; D018418:Th2 Cells / Q000166:cytology / Q000378:metabolism*; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism*
chemical_list: D039041:Integrin alpha4beta1; D016023:Integrins; D008222:Lymphokines; D016201:Receptors, Lymphocyte Homing; D019010:Vascular Cell Adhesion Molecule-1; D017493:Leukocyte Common Antigens