Induction of αvβ3 integrin-mediated attachment to extracellular matrix in β1 integrin (CD29)-negative B cell lines

Abstract

β 1 integrin containing complexes have been implicated as the primary adhesion structures in many lymphocyte extracellular matrix (ECM) interactions. However, many B lymphocytes lack surface expression of the β 1 subunit, implying that this subpopulation of lymphoid cells must employ alternate adhesion structures if they are to maintain an interactive capacity with ECM. An examination of the adherence properties of the β 1 integrin-negative B cell line JY indicated that these cells exhibit little or no basal adherence to any of the ECM components examined. However, these cells could be induced to adhere to the ECM components fibronectin, laminin, and vitronectin following treatment with PMA. Blocking studies with monoclonal antibodies indicated the α v β 3 integrin complex was involved in the attachment to each of these ligands. However, the adherence to fibronectin displayed a complex pattern of inhibition suggesting the involvement of other ECM receptors. The utilization of the α v β 3 complex was not unique to the JY cell line. Other B cell lines were observed to employ α v β 3, and these lines similarly lacked expression of β 1 integrin. These results indicate that α v β 3 can act as a lymphoid ECM-adhesion structure which may provide an alternative means for lymphocytes to interact with ECM. Furthermore, these studies provide evidence for the presence of lymphoid-associated α v β 3 integrins with regulatable activity, which contrasts with the constitutive adhesive potential of these complexes when present on other cell types.