Analysis of the activation state of alpha 4 beta 1 integrin in human B cell lines derived from myeloma, leukemia or lymphoma

Myeloma cells specifically localize in the bone marrow and rarely circulate in blood. To study whether this immobilization could be partially extplained by the presence of constitutively activated integrins, particularly alpha 4 beta 1, we used the activation reporter HUTS-21 anti-beta 1 mAb. These analyses showed that beta 1 integrins on myeloma cells were moderately active and could be upregulated similarly to integrins on lymphoma or leukemia cells. Myeloma cells mere also tested for their ability to attach to RGD-containing fibronectin fragments, a property of activated (but not resting) alpha 4 beta 1. Two cell lines adhered to these fragments and this was inhibited by anti-alpha 5 but not by anti-alpha 4 mAbs, These results show that myeloma cells bear low/moderately active alpha 4 beta 1 and support the notion that multiple interactions contribute to their localization in the bone marrow. (C) 1997 Federation of European Biochemical Societies.