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α4β7 Integrin mediates B cell binding to fibronectin and vascular cell adhesion molecule-1: Expression and function of α4 integrins on human B lymphocytes

Abstract:

Cell-cell and cell-extracellular matrix interactions are mediated by a wide array of cell surface molecules known as adhesion receptors, including the integrin family that comprises numerous αβ heterodimers. A new integrin group, the β7 subfamily, has been recently defined. Its two members, α4β7 and α(H)β7, are involved in the lymphocyte migration to the Peyer's patches and the intestinal mucosa, respectively. We have analyzed the expression of α4β7 integrin on B cells from different cellular compartments and at different activation states. Resting peripheral blood B lymphocytes constitutively express large amounts of α4β7. By contrast, α4β7 integrin, which is absent on resident B cells from different lymphoid tissues, is induced upon activation. Functional studies indicates that α4β7 is mediating B cell attachment to fibronectin and vascular cell adhesion molecule-1 through distinct epitopes on this integrin. Furthermore, the α4β7 integrin is also implicated in intercellular interactions as deduced by the ability of anti-α4β7 mAb to trigger homotypic B cell aggregation. Finally, α4β7 and α4β1 integrins bkp_redistribute at the cell membrane in a similar clustering pattern when B cells attach to fibronectin- and vascular cell adhesion molecule-1-coated surfaces. Our studies demonstrate the differential regulation on the expression and function of α4β7 integrin among different human B cell populations.