INTEGRIN VLA-6 (ALPHA-6-BETA-1) MEDIATES ADHESION OF MOUSE BONE-MARROW-DERIVED MAST-CELLS TO LAMININ

The development of mast cells from bone marrow precursors and their fu nction as the mucosal- or connective-tissue-type mast cell are critica lly dependent on microenvironmental factors. Extracellular matrix prot eins, such as collagen, fibronectin, and laminin, may represent insolu ble components of the microenvironment. Recent studies have described multiple isoforms of laminin isolated from different tissues. In the p resent study, adhesion of mouse bone marrow-derived mast cells (BMMC) and long-term mast cell lines to Engelbreth-Holm-Swarm (EHS) tumor lam inin, rat laminin, human merosin, and human placental laminin was comp ared. The greatest level of adhesion was found with human laminin as t he substrate. By use of a newly prepared mouse VLA-alpha 6 integrin-sp ecific mAb (MA6) together with the previously described mAb GoH3, VLA- 6 (alpha 6 beta 1) integrin was found to be expressed and utilized by BMMC and long-term mast cell Lines. VLA-6 has been described as a majo r laminin receptor with roles in diverse cell functions including cell growth and differentiation. BMMC have been shown to express a 32/67-k Da laminin receptor. Therefore, in addition to the 32/67-kDa laminin r eceptor described in early studies, BMMC also express VLA-6 integrin, which may have roles in the regulation of their development.