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 circ ulate in blood. To study whether this immobilization could be partiall y extplained by the presence of constitutively activated integrins, pa rticularly alpha 4 beta 1, we used the activation reporter HUTS-21 ant i-beta 1 mAb. These analyses showed that beta 1 integrins on myeloma c ells were moderately active and could be upregulated similarly to inte grins on lymphoma or leukemia cells. Myeloma cells mere also tested fo r their ability to attach to RGD-containing fibronectin fragments, a p roperty 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 l ow/moderately active alpha 4 beta 1 and support the notion that multip le interactions contribute to their localization in the bone marrow. ( C) 1997 Federation of European Biochemical Societies.