Constitutive αVβ3 integrin-mediated adhesion of human lymphoid B cells to vitronectin substrate

Adherence to cells and matrices participates in lymphocyte migration and tissue localization and contributes to the regulation of growth and differentiation of the lymphoid cells. The adherence is mainly mediated by three families of cell-surface proteins: integrins, immunoglobulin (Ig)-related molecules, and selectins. Integrins recognize Ig-related molecules such as ICAMs as well as fibronectin (FN), vitronectin (VN), and other matrix proteins. In this study, the in vitro adhesive properties of two Epstein—Barr virus-carrying B lymphoblastoid cell lines, IB-4 and NAD-20, were compared. IB-4 cells grow as a monolayer in contrast to NAD-20 cells, which grow as cell clusters. IB-4 cells were found to adhere to the tissue culture vessel through a component of the fetal bovine serum. By using blocking monoclonal antibodies to cell-surface molecules and serum proteins, IB-4 cells were found to use αVβ3 integrin (CD51/CD61) and serum VN as the adhesive molecules. αVβ3 integrin also mediated adhesion of IB-4 cells to human serum VN and to purified VN and FN. This constitutive adherence was not enhanced by phorbol ester treatment and was inhibited by RGD-containing peptides, in contrast to the homotypic adhesion of NAD-20 cells, which was mediated by β2 integrin CD11a/CD18 and its ligand ICAM-1 (CD54). Since VN is a component of both lymphoid tissue matrix and plasma, adhesion to this protein may affect functions and activities of B lymphocytes.